JP3135181U - Sensor that detects both acceleration and angular velocity - Google Patents

Abstract

PROBLEM TO BE SOLVED: To detect static and dynamic acceleration and angular velocity while adopting a simple structure.
A doughnut-shaped annular groove 140 is dug on the lower surface of a main substrate 100 to form an annular intermediate portion 120 having a small thickness. A weight body 210 is joined below the inner portion 110. The annular intermediate part 120 has flexibility, and the weight body 210 can be displaced with respect to the outer part 130. A piezoresistive element P is embedded in the surface layer of the annular intermediate portion 120, and piezoelectric elements D1, D2, E1, and E2 are fixed to the upper surface thereof. When the weight body 210 is displaced by acceleration, the annular intermediate portion 120 is bent, and acceleration is detected as a change in the electric resistance of the piezoresistive element P. When the weight body 210 is displaced by the Coriolis force based on the angular velocity in the state in which the weight body 210 is vibrated by supplying an AC signal to the piezoelectric elements E1 and E2, the annular intermediate portion 120 is bent, and the piezoelectric elements D1 and D2 are deformed. Angular velocity is detected by the generated charge.
[Selection] Figure 2

Description

  The present invention relates to a sensor that detects both acceleration and angular velocity, and more particularly to a sensor that detects acceleration and angular velocity based on a force acting on a weight body.

  Industrial machines and electronic devices often incorporate devices that detect physical quantities such as acceleration and angular velocity. For this reason, many small and highly accurate acceleration sensors and angular velocity sensors have been developed. In particular, there is an increasing demand for multi-axis acceleration sensors that can detect acceleration in two or three dimensions and multi-axis angular velocity sensors that can detect angular velocities around two or three axes. For example, many recent digital cameras incorporate a multi-axis acceleration sensor, a multi-axis angular velocity sensor, or the like in order to perform camera shake control. In such applications, downsizing of the sensor is an important issue, and a single-purpose device that can detect both acceleration and angular velocity (generally called a motion sensor). Is desired).

In order to meet such a demand, the inventor of the present application has proposed a sensor capable of detecting both acceleration and angular velocity. For example, in Patent Documents 1 and 2 below, both acceleration and angular velocity are detected by electrically detecting displacement of a weight body (vibrator) caused by the action of acceleration or angular velocity as bending of a piezoelectric element. A sensor is disclosed. Patent Document 3 discloses a sensor that detects both acceleration and angular velocity by electrically detecting displacement of a weight body (vibrator) as a change in capacitance value of a capacitance element. Has been.
JP-A-8-068636 JP 2002-350138 A JP 2005-031096 A

  The above-mentioned type of sensor using a piezoelectric element utilizes the property of a piezoelectric element that an electric charge is generated when mechanical deformation is applied. Therefore, “dynamic displacement of the weight body (transient movement)” can be detected, but “static displacement of the weight body (deviation amount from the fixed position)” cannot be detected. . Therefore, with regard to angular velocity detection based on the assumption that the weight body is moved, static angular velocity (angular velocity of motion that always rotates at a constant speed in a constant direction) is also dynamic angular velocity (rotation direction and speed is time Can be detected, but with regard to acceleration detection, dynamic acceleration (change in the magnitude and direction of acceleration over time) can be detected, but static acceleration (for example, In other words, it is impossible to detect constant acceleration (such as gravitational acceleration). For example, when a force is applied to the piezoelectric element, a predetermined charge is initially generated as a transient response. However, if the applied force is constant, no charge can be generated after the measurement system is stabilized. . Therefore, constant acceleration (static acceleration) cannot be detected as in the case of gravitational acceleration.

  On the other hand, the above-mentioned type of sensor using the capacitive element can detect the displacement of the weight body itself as the capacitance value (distance between electrodes) of the capacitive element. Any of dynamic angular velocity, static acceleration, and dynamic acceleration can be detected. However, since it is necessary to provide wiring for each of the pair of electrodes constituting the capacitance element, the structure of the entire sensor must be complicated. In particular, in order to obtain a highly accurate detection value, when air that functions as a damper is removed from the periphery of the weight body and the inside is evacuated, wiring is performed to the internal electrodes while maintaining a vacuum state. Since a need arises, a very complex structure is required.

  Accordingly, an object of the present invention is to provide a sensor capable of detecting both static and dynamic angular velocities and static and dynamic acceleration while adopting a simple structure.

(1) The first aspect of the present invention is a sensor that detects both acceleration and angular velocity.
An annular groove is formed on the lower surface, and has an inner part located inside the annular groove forming area, an outer part located outside the annular groove forming area, and an annular intermediate part located in the annular groove forming area, The annular intermediate portion is flexible so that the inner portion can be displaced with respect to the outer portion, and
A weight body connected to the lower surface of the inner part;
A pedestal connected to the lower surface of the outer portion and fixed to the apparatus housing so as to surround the weight body;
A piezoresistive element embedded in the annular intermediate part;
A driving piezoelectric element and a detecting piezoelectric element fixed to the surface of the annular intermediate portion;
An acceleration detection circuit for detecting an acceleration acting based on a change in electrical resistance of the piezoresistive element;
An angular velocity that detects the angular velocity acting on the basis of the signal generated in the detecting piezoelectric element while supplying an alternating current signal to the driving piezoelectric element to periodically deform the annular intermediate portion and causing the weight body to periodically move. A detection circuit;
It is made up by.

(2) A second aspect of the present invention is a sensor for detecting both acceleration and angular velocity according to the first aspect described above,
The acceleration detection circuit has a low-pass filter circuit that cuts a high-frequency component included in a signal indicating a change in the electrical resistance of the piezoresistive element, and the signal component that has passed through the low-pass filter circuit is used as an acceleration detection value. Output,
The angular velocity detection circuit supplies an AC signal to the drive piezoelectric element to control the periodic movement of the weight body, and a high frequency cut off low frequency component included in the AC signal generated in the detection piezoelectric element. A detection result by the synchronous detection circuit, and a synchronous detection circuit that performs synchronous detection based on a detection signal given from the drive control circuit with respect to the AC signal that has passed through the high-pass filter circuit. Is output as a detected value of angular velocity.

(3) A third aspect of the present invention is a sensor that detects both acceleration and angular velocity according to the first or second aspect described above,
The contour line of the projected image when the weight body is vertically projected onto the upper surface of the main body substrate is positioned outside the inner portion of the main body substrate.

(4) A fourth aspect of the present invention is a sensor for detecting both acceleration and angular velocity according to the first to third aspects described above,
When the annular groove is vertically projected on the upper surface of the main body substrate, the inner contour line and the outer contour line of the projected image form concentric circles,
The weight body has a columnar shape having a central axis at “an axis orthogonal to the upper surface of the main body substrate and passing through the center of the concentric circle”.

(5) A fifth aspect of the present invention is a sensor for detecting both acceleration and angular velocity according to the first to fourth aspects described above,
The piezoresistive element, the driving piezoelectric element, and the detecting piezoelectric element are arranged at positions in contact with the inner contour line or the outer contour line of the annular groove forming region.

(6) A sixth aspect of the present invention is a sensor for detecting both acceleration and angular velocity according to the first to fifth aspects described above,
The main body substrate is constituted by a single silicon substrate or SOI substrate, and the piezoresistive element is constituted by a silicon impurity-containing layer formed on the surface layer portion of the main body substrate.

(7) A seventh aspect of the present invention is a sensor for detecting both acceleration and angular velocity according to the first to sixth aspects described above,
An XYZ three-dimensional coordinate system is defined such that the origin O is located at the center of the inner part of the upper surface of the main body substrate and the XY plane is located on the upper surface of the main body substrate. When defining the neighborhood part as the inner neighborhood area and the neighborhood part of the outer contour line as the outer neighborhood area,
A first X-axis detection piezoresistive element is disposed in the outer vicinity region on the positive X-axis, and a second X-axis detection piezoresistive element is disposed in the inner vicinity region on the positive X-axis. A third X-axis detection piezoresistive element is disposed in the inner vicinity region on the X-axis, and a fourth X-axis detection piezoresistive element is disposed in the outer vicinity region on the negative X-axis;
A first Y-axis detection piezoresistive element is disposed in the outer vicinity region on the positive Y-axis, and a second Y-axis detection piezoresistive element is disposed in the inner vicinity region on the positive Y-axis. A third Y-axis detecting piezoresistive element is disposed in the inner vicinity region on the Y-axis, and a fourth Y-axis detecting piezoresistive element is disposed in the outer vicinity region on the negative Y-axis,
A first Z-axis detection piezoresistive element is disposed at an arbitrary position in the outer vicinity area, and a second Z-axis detection piezoresistive element is disposed at an arbitrary position in the inner vicinity area. A third Z-axis detecting piezoresistive element is disposed at a position, and a fourth Z-axis detecting piezoresistive element is disposed at an arbitrary position in the outer vicinity region;
The acceleration detection circuit has the first X-axis detection piezoresistive element and the third X-axis detection piezoresistive element as the first opposite side, and the second X-axis detection piezoresistive element and the fourth X-axis detection. The first Y-axis detecting piezoresistive element and the third Y-axis detecting piezo element are detected by detecting acceleration acting in the X-axis direction based on the bridge voltage of the bridge circuit having the piezoresistive element as the second opposite side. Acting in the Y-axis direction based on the bridge voltage of the bridge circuit having the resistance element as the first opposite side and the second Y-axis detection piezoresistance element and the fourth Y-axis detection piezoresistance element as the second opposite side The first Z-axis detecting piezoresistive element and the fourth Z-axis detecting piezoresistive element are set as the first opposite sides, and the second Z-axis detecting piezoresistive element and the third Z-axis detecting element are detected. The axis detecting piezoresistive element is connected to the second opposite side. That on the basis of the bridge voltage of the bridge circuit is obtained so as to detect the acceleration applied in the Z-axis direction.

(8) An eighth aspect of the present invention is a sensor for detecting both acceleration and angular velocity according to the first to seventh aspects described above,
An XYZ three-dimensional coordinate system is defined such that the origin O is located at the center of the inner part of the upper surface of the main body substrate and the XY plane is located on the upper surface of the main body substrate. When defining the neighborhood part as the inner neighborhood area and the neighborhood part of the outer contour line as the outer neighborhood area,
One of the inner vicinity area and the outer vicinity area is set as a driving piezoelectric element arrangement area, and the other is set as a detection piezoelectric element arrangement area,
The first driving piezoelectric element is arranged on the positive X axis in the driving piezoelectric element arrangement region, the second driving piezoelectric element is arranged on the negative X axis, and the third driving piezoelectric element is arranged on the positive Y axis. A driving piezoelectric element is disposed, and a fourth driving piezoelectric element is disposed on the negative Y-axis,
The first detection piezoelectric element is arranged on the positive X axis in the detection piezoelectric element arrangement region, the second detection piezoelectric element is arranged on the negative X axis, and the third detection piezoelectric element is arranged on the positive Y axis. A detection piezoelectric element is disposed, and a fourth detection piezoelectric element is disposed on the negative Y axis.
The angular velocity detection circuit supplies an alternating current signal whose phase is shifted by π / 2 to each driving piezoelectric element, thereby causing the weight body to move in a plane parallel to the XY plane while the weight body is XZ. Based on the difference between the signal generated in the first detection piezoelectric element and the signal generated in the second detection piezoelectric element at the time of passing through the plane, the angular velocity around the Z axis is detected, and the weight body passes through the XZ plane. The angular velocity around the X axis is detected based on the sum of the signal generated in the third detection piezoelectric element and the signal generated in the fourth detection piezoelectric element at the time when the weight body passes through the YZ plane. The angular velocity around the Y axis is detected based on the sum of the signal generated in the third detection piezoelectric element and the signal generated in the fourth detection piezoelectric element.

(9) A ninth aspect of the present invention is a sensor for detecting both acceleration and angular velocity according to the first to seventh aspects described above,
An XYZ three-dimensional coordinate system is defined such that the origin O is located at the center of the inner part of the upper surface of the main body substrate and the XY plane is located on the upper surface of the main body substrate. When defining the neighborhood part as the inner neighborhood area and the neighborhood part of the outer contour line as the outer neighborhood area,
One of the inner vicinity area and the outer vicinity area is set as a driving piezoelectric element arrangement area, and the other is set as a detection piezoelectric element arrangement area,
A first driving piezoelectric element is disposed on the positive X axis in the driving piezoelectric element arrangement region, and a second driving piezoelectric element is disposed on the negative X axis;
The first detection piezoelectric element is arranged on the positive X axis in the detection piezoelectric element arrangement region, the second detection piezoelectric element is arranged on the negative X axis, and the third detection piezoelectric element is arranged on the positive Y axis. A detection piezoelectric element is disposed, and a fourth detection piezoelectric element is disposed on the negative Y axis.
The angular velocity detection circuit supplies an alternating current signal whose phase is shifted by π / 2 to the first driving piezoelectric element and the second driving piezoelectric element, whereby the weight body is circular in the XZ plane. The angular velocity about the Y axis based on the difference between the signal generated in the first detection piezoelectric element and the signal generated in the second detection piezoelectric element when the weight body moves in the Z-axis direction while moving. And the angular velocity around the X axis based on the difference between the signal generated in the third detection piezoelectric element and the signal generated in the fourth detection piezoelectric element at the time when the weight body moves in the Z-axis direction. And the angular velocity around the Z axis based on the difference between the signal generated in the third detection piezoelectric element and the signal generated in the fourth detection piezoelectric element when the weight body moves in the X-axis direction. Is to be detected.

(10) A tenth aspect of the present invention is a sensor for detecting both acceleration and angular velocity according to the first to seventh aspects described above,
An XYZ three-dimensional coordinate system is defined such that the origin O is located at the center of the inner part of the upper surface of the main body substrate and the XY plane is located on the upper surface of the main body substrate. When defining the neighborhood part as the inner neighborhood area and the neighborhood part of the outer contour line as the outer neighborhood area,
One of the inner vicinity area and the outer vicinity area is set as a driving piezoelectric element arrangement area, and the other is set as a detection piezoelectric element arrangement area,
An annular driving piezoelectric element surrounding the Z axis is arranged in the driving piezoelectric element arrangement region,
The first detection piezoelectric element is arranged on the positive X axis in the detection piezoelectric element arrangement region, the second detection piezoelectric element is arranged on the negative X axis, and the third detection piezoelectric element is arranged on the positive Y axis. A detection piezoelectric element is disposed, and a fourth detection piezoelectric element is disposed on the negative Y axis.
The angular velocity detection circuit supplies a single alternating current signal to the driving piezoelectric element, so that the signal generated in the first detection piezoelectric element and the second are generated while vibrating the weight body in the Z-axis direction. An angular velocity around the Y axis is detected based on the difference between the signal generated in the detection piezoelectric element and X based on the difference between the signal generated in the third detection piezoelectric element and the signal generated in the fourth detection piezoelectric element. The angular velocity around the axis is detected.

(11) An eleventh aspect of the present invention is a sensor for detecting both acceleration and angular velocity according to the first to seventh aspects described above,
When an XYZ three-dimensional coordinate system is defined such that the origin O is located at the center of the inner side of the upper surface of the main body substrate and the XY plane is located on the upper surface of the main body substrate,
A first drive piezoelectric element is disposed on the positive X axis, a second drive piezoelectric element is disposed on the negative X axis, and a first detection piezoelectric element is disposed on the positive Y axis. , A second detection piezoelectric element is disposed on the negative Y-axis,
The angular velocity detection circuit supplies alternating current signals having opposite phases to the first driving piezoelectric element and the second driving piezoelectric element, thereby vibrating the weight body in the X-axis direction. Both the acceleration and the angular velocity are characterized in that the angular velocity around the Z-axis is detected based on the difference between the signal generated in the first detecting piezoelectric element and the signal generated in the second detecting piezoelectric element. Is.

(12) A twelfth aspect of the present invention is a sensor for detecting both acceleration and angular velocity according to the first to eleventh aspects described above,
A lower electrode is formed on the lower surface of the driving piezoelectric element and the detecting piezoelectric element, and an upper electrode is formed on the upper surface. The lower electrode of each piezoelectric element is fixed to the upper surface of the annular intermediate portion via an insulating layer. Has been
The angular velocity detection circuit applies an AC voltage between the upper electrode and the lower electrode of the driving piezoelectric element to cause a periodic motion in the weight body, while the upper electrode and the lower electrode of the detection piezoelectric element Both the acceleration and the angular velocity, which are characterized by detecting the angular velocity acting based on the AC voltage generated between them, are detected.

(13) An eleventh aspect of the present invention is a sensor for detecting both acceleration and angular velocity according to the twelfth aspect,
The lower electrodes of the plurality of piezoelectric elements are physically constituted by a single common conductive layer.

(14) A fourteenth aspect of the present invention is a sensor that detects both acceleration and angular velocity according to the twelfth or thirteenth aspect described above,
A plurality of piezoelectric elements are physically constituted by a single common piezoelectric element layer.

(15) A fifteenth aspect of the present invention is a sensor that detects both acceleration and angular velocity according to the twelfth aspect described above,
A common insulating layer is formed on the upper surface of the main substrate, a lower common conductive layer is formed on the upper surface of the common insulating layer, and individual piezoelectric element layers are formed on the upper surface of the lower common conductive layer. Each upper individual conductive layer is formed on the upper surface,
Each upper individual conductive layer constitutes an upper electrode of each drive piezoelectric element and each detection piezoelectric element, and each individual piezoelectric element layer constitutes each drive piezoelectric element and each detection piezoelectric element, and the lower common conductive layer. The individual parts of the layer constitute the lower electrode of each driving piezoelectric element and each detecting piezoelectric element,
On the upper surface of the lower common conductive layer, a piezoelectric element patterning layer patterned along the wiring path for each upper electrode is formed,
The wiring layer for each piezoresistive element is embedded in the common insulating layer,
The wiring layer for each upper electrode is formed on the upper surface of the piezoelectric element patterning layer.

(16) A sixteenth aspect of the present invention is a sensor for detecting both acceleration and angular velocity according to the twelfth aspect,
A common insulating layer is formed on the upper surface of the main substrate, a lower common conductive layer is formed on the upper surface of the common insulating layer, a common piezoelectric element layer is formed on the upper surface of the lower common conductive layer, and an upper surface of the common piezoelectric element layer. In each case, an upper individual conductive layer is formed,
Each upper individual conductive layer constitutes an upper electrode of each drive piezoelectric element and each detection piezoelectric element, and each drive piezoelectric element and each detection piezoelectric element is constituted by an individual portion of the common piezoelectric element layer, The lower electrode of each driving piezoelectric element and each detecting piezoelectric element is constituted by individual portions of the lower common conductive layer,
The wiring layer for each piezoresistive element is embedded in the insulating layer,
The wiring layer for each upper electrode is formed on the upper surface of the common piezoelectric element layer.

(17) A seventeenth aspect of the present invention is a sensor for detecting both acceleration and angular velocity according to the first to sixteenth aspects described above,
In some regions, the piezoresistive element and the piezoelectric element are formed so as to be in a laminated state with at least an insulating layer interposed therebetween.

  In the sensor according to the present invention, a weight body is connected to the inner side portion of the main body substrate having an annular groove formed on the lower surface, and the weight body is supported from the periphery by an annular intermediate portion having flexibility. The detected acceleration or angular velocity is detected by detecting the displacement of the weight body. In addition, the acceleration is detected based on a change in electrical resistance of the piezoresistive element formed in the annular intermediate portion, and the angular velocity is detected by a piezoelectric element formed in the annular intermediate portion. Since both the piezoresistive element and the piezoelectric element are formed in the annular intermediate portion, the structure of the entire sensor can be simplified. In addition, when performing detection using a piezoresistive element or a piezoelectric element, it is not necessary to measure a minute change in electrode spacing as in the case of detection using a capacitive element. Absent. Moreover, the piezoresistive element can detect the static acceleration as an electric resistance value even in a state where static acceleration (for example, gravitational acceleration) is applied. Acceleration can be detected. As described above, the sensor according to the present invention can detect both static and dynamic angular velocities and static and dynamic acceleration while adopting a simple structure.

  Hereinafter, the present invention will be described based on the illustrated embodiment.

<<< §1. Structure of sensor according to basic embodiment >>
FIG. 1 is a top view showing an example of a sensor according to a basic embodiment of the present invention. As shown in the figure, a state is shown in which eight fan-shaped piezoelectric elements D1 to D4 and E1 to E4 are arranged on the upper surface of the square main body substrate 100, respectively. Here, for convenience of explanation, the origin O is set at the center position of the upper surface of the main body substrate 100, the X axis is set in the right direction in FIG. Define the system. 1 is a piezoresistive element P embedded in the upper surface of the main body substrate 100, and its arrangement will be described in detail later. Further, the Xa axis and the Xb axis shown in FIG. 1 are auxiliary axes defined on both sides of the X axis, and some of the piezoresistive elements P are disposed along these auxiliary axes.

  FIG. 2 is a sectional side view of the sensor shown in FIG. 1 taken along the XZ plane. As shown in the figure, the basic structure of the sensor is composed of three substrates: a main substrate 100, an auxiliary substrate 200, and a support substrate 300. In the embodiment shown here, the main body substrate 100 is formed of a silicon substrate, the auxiliary substrate 200 is formed of a glass substrate, and the support substrate 300 is formed of a silicon substrate. FIG. 3 shows a cross-sectional view of the sensor cut along the cutting line 3-3, and FIG. 4 shows a cross-sectional view cut along the cutting line 4-4.

  The main body substrate 100 is a square substrate composed of three parts, an inner part 110, an annular intermediate part 120, and an outer part 130, and an annular groove 140 is formed on the lower surface thereof. As clearly shown in the plan sectional view of FIG. 3, the annular groove 140 is a washer-like gap portion, and a portion located inside the annular groove 140 formation region becomes a cylindrical inner portion 110, The portion located outside becomes the outer portion 130. The annular groove 140 is an annular groove dug on the lower surface side of the main body substrate 100. As shown in FIG. 2, the annular intermediate portion 120 located immediately above the annular groove 140 is thin. It functions as a diaphragm. In other words, the annular intermediate portion 120 is a thin-walled structure (its plan view is the same as the plan view of the annular groove 140 shown in FIG. 3) located in the annular groove forming region, The portion 110 is flexible so that it can be displaced with respect to the outer portion 130. The annular groove 140 can also be a toroidal groove.

  On the other hand, as shown in FIG. 4, the auxiliary substrate 200 includes a prismatic weight body 210 having a square cross section and a pedestal 220 surrounding the weight body 210. As shown in FIG. 2, a cylindrical protrusion (thickness d1) having the same diameter as that of the inner portion 110 is formed on the upper surface of the weight body 210. It is connected to the lower surface of the part 110. Further, the upper surface of the pedestal 220 is connected to the lower surface of the outer portion 130, and the lower surface of the pedestal 220 is connected to the upper surface of the support substrate 300. The support substrate 300 is fixed to an apparatus housing (not shown) that encloses the entire components shown in FIG. Eventually, the pedestal 220 is fixed to the apparatus housing via the support substrate 300.

  As shown in FIG. 2, a gap dimension d <b> 1 is secured between the upper surface of the weight body 210 and the lower surface of the outer portion 130, and the outer peripheral surface of the weight body 210 and the inner peripheral surface of the base 220. A gap dimension d2 is secured between them (see also FIG. 4), and a gap dimension d3 is secured between the lower surface of the weight body 210 and the upper surface of the support substrate 300. Therefore, in a state where no force is applied, the weight body 210 is suspended from above via the inner portion 110.

  2, constituent elements D1, D2, E1, and E2 disposed on the upper surface of the main body substrate 100 are a part of the eight piezoelectric elements D1 to D4 and E1 to E4 shown in FIG. In FIG. 2, the constituent element embedded in the surface layer portion on the upper surface of the main substrate 100 is the piezoresistive element P described above.

  FIG. 5 is a top view showing a state where the piezoelectric elements D1 to D4 and E1 to E4 are removed from the sensor shown in FIG. 1 in order to clearly show the planar arrangement of the piezoresistive elements P. The broken-line circles in the figure are the inner contour line C1 and the outer contour line C2 of the annular groove 140, and the inner side of the inner contour line C1 is the inner portion 110, between the inner contour line C1 and the outer contour line C2 (annular groove). The formation region) is the annular intermediate portion 120, and the outer side of the outer contour line C2 is the outer portion 130.

  As illustrated, a total of 12 sets of piezoresistive elements Px1 to Px4, Py1 to Py4, and Pz1 to Pz4 are embedded on the upper surface of the main body substrate 100, all of which are portions of the annular intermediate portion 120 (annular groove forming region). ). Moreover, among the parts belonging to the annular intermediate portion 120, if the vicinity of the inner contour line C1 is defined as the inner vicinity region, and the vicinity of the outer contour line C2 is defined as the outer vicinity region, six sets of piezoresistive elements Px2, Px3, Py2, Py3, Pz2, Pz3 are arranged in the inner vicinity region, the inner end thereof is in contact with the inner contour line C1, and the remaining six sets of piezoresistive elements Px1, Px4, Py1, Py4, Pz1, Pz4 are It arrange | positions at an outer side vicinity area | region, and the outer side edge has touched the outer side outline C2. The reason why the piezoresistive elements are arranged in the inner vicinity area and the outer vicinity area is that stress is concentrated in these areas when an external force is applied to the weight body 210 as will be described later. . That is, the detection sensitivity is increased by arranging each piezoresistive element at a location where stress is most likely to be concentrated.

  The piezoresistive elements Px1 to Px4 are used to detect acceleration acting in the X-axis direction, and are referred to as X-axis detecting piezoresistive elements here. Similarly, since the piezoresistive elements Py1 to Py4 are used to detect acceleration acting in the Y-axis direction, they are referred to herein as Y-axis detecting piezoresistive elements, and the piezoresistive elements Pz1 to Pz4 are referred to as the Z-axis direction. Since it is used to detect the acceleration acting on the, it will be referred to as a Z-axis detecting piezoresistive element here.

  The arrangement of the individual piezoresistive elements shown in FIG. 5 will be described more specifically as follows. That is, as shown in the drawing, an XYZ three-dimensional coordinate system is defined such that the origin O is located at the center of the inner part 110 on the upper surface of the main body substrate 100 and the XY plane is located on the upper surface of the main body substrate 100. Of the belonging parts, if the vicinity of the inner contour line C1 is defined as the inner vicinity region, and the vicinity of the outer contour line C2 is defined as the outer vicinity region, the first X axis detection for the outer vicinity region on the positive X axis The piezoresistive element Px1 is disposed, the second X-axis detecting piezoresistive element Px2 is disposed in the inner vicinity region on the positive X-axis, and the third X-axis detecting element is disposed in the inner vicinity region on the negative X-axis. A piezoresistive element Px3 is arranged, and a fourth X-axis detecting piezoresistive element Px4 is arranged in the outer vicinity region on the negative X-axis. In this way, the acceleration acting in the X-axis direction is detected by the four sets of piezoresistive elements Px1 to Px4 arranged on the X-axis.

  Similarly, for the Y-axis detecting piezoresistive element, the first Y-axis detecting piezoresistive element Py1 is arranged in the outer vicinity region on the positive Y-axis, and the second in the inner vicinity region on the positive Y-axis. Y-axis detecting piezoresistive element Py2 is arranged, a third Y-axis detecting piezoresistive element Py3 is arranged in the inner vicinity region on the negative Y-axis, and the fourth in the outer neighboring region on the negative Y-axis. Y-axis detecting piezoresistive element Py4 is arranged. As described above, the acceleration acting in the Y-axis direction is detected by the four sets of piezoresistive elements Py1 to Py4 arranged on the Y-axis.

  For the Z-axis detecting piezoresistive element, auxiliary axes Xa and Xb parallel to the X-axis are defined on both sides of the X-axis, and the first Z-axis detecting element is located in the outer vicinity region on the positive Xb-axis. The piezoresistive element Pz1 is disposed, the second Z-axis detecting piezoresistive element Pz2 is disposed in the inner vicinity region on the positive Xb axis, and the third Z-axis detecting element is disposed in the inner vicinity region on the negative Xa axis. A piezoresistive element Pz3 is disposed, and a fourth Z-axis detecting piezoresistive element Pz4 is disposed in the outer vicinity region on the negative Xa axis.

  Thus, in the illustrated example, the Z-axis detection piezoresistive elements Pz1 to Pz4 are arranged on the auxiliary axes Xa and Xb defined on both sides of the X-axis. Pz1 to Pz4 are not necessarily arranged on both sides of the X axis. In principle, the first Z-axis detection piezoresistive element Pz1 is arranged at an arbitrary position in the outer vicinity area, and the second Z-axis detection piezoresistive element Pz2 is set at an arbitrary position in the inner vicinity area. The third Z-axis detecting piezoresistive element Pz3 is arranged at an arbitrary position in the inner vicinity area, and the fourth Z-axis detecting piezoresistive element Pz4 is arranged at an arbitrary position in the outer neighboring area. That's fine.

  In order to increase the detection sensitivity, each piezoresistive element is preferably an elongated shape extending substantially along a radial direction centered on the origin O (radial direction of the circle C2). An acceleration detection circuit, which will be described later, detects acceleration that has acted on the basis of changes in the electrical resistance of these piezoresistive elements.

  On the other hand, eight sets of piezoelectric elements D1 to D4 and E1 to E4 shown in FIG. 1 are fixed to the surface of the annular intermediate portion 120. Moreover, the piezoelectric elements D1 to D4 are disposed in the inner vicinity region, and the inner peripheral edge thereof is in contact with the inner contour line C1 (see FIG. 5). Further, the piezoelectric elements E1 to E4 are arranged in the outer vicinity region, and the outer peripheral edge thereof is in contact with the outer contour line C2 (see FIG. 5). The reason why such an arrangement is adopted is that stress is concentrated in these areas when an external force is applied to the weight body 210.

  The eight sets of piezoelectric elements are elements having the same physical configuration, but here, in consideration of the use, the detection piezoelectric elements D1 to D4 and the driving piezoelectric elements E1 to E1 are used. It will be divided into E4. As will be described in detail later, in the case of the sensor shown in FIG. 1, the four sets of piezoelectric elements D1 to D4 arranged in the inner vicinity area serve as detection piezoelectric elements, and the four sets of piezoelectric elements E1 to E1 arranged in the outer vicinity area. E4 is a driving piezoelectric element. An angular velocity detection circuit, which will be described later, supplies an alternating current signal to the driving piezoelectric elements E1 to E4, periodically deforms the annular intermediate portion 120, and causes periodic motion in the weight body 210, while detecting piezoelectricity. An angular velocity acting on the basis of signals generated in the elements D1 to D4 is detected.

  The positions of the detecting piezoelectric elements D1 to D4 and the driving piezoelectric elements E1 to E4 may be interchanged. That is, the detection piezoelectric elements D1 to D4 shown in FIG. 1 are used as drive piezoelectric elements E1 to E4 as they are, and the drive piezoelectric elements E1 to E4 shown in FIG. 1 are used as they are as detection piezoelectric elements D1 to D4. It may be used as D4.

  In short, one of the inner vicinity region and the outer vicinity region is set as a driving piezoelectric element arrangement region, and the other is set as a detection piezoelectric element arrangement region (in the example of FIG. 1, the inner vicinity region is set as a detection piezoelectric element. In this example, the outer vicinity region is determined as the driving piezoelectric element arrangement region), the first driving piezoelectric element E1 is arranged on the positive X axis of the driving piezoelectric element arrangement region, and the negative A second driving piezoelectric element E2 is arranged on the X axis, a third driving piezoelectric element E3 is arranged on the positive Y axis, and a fourth driving piezoelectric element E4 is arranged on the negative Y axis. The first detection piezoelectric element D1 is arranged on the positive X axis in the detection piezoelectric element arrangement region, the second detection piezoelectric element D2 is arranged on the negative X axis, and the positive The third detection piezoelectric element D3 is disposed on the Y axis, and the fourth detection piezoelectric element is disposed on the negative Y axis. 4 it suffices to be placed.

  In the piezoelectric elements for detection D1 to D4 and the piezoelectric elements for driving E1 to E4, the bending generated on the upper surface of the annular intermediate portion 120 is transmitted to each piezoelectric element, and conversely, the bending generated in each piezoelectric element is annular intermediate. What is necessary is just to adhere to the predetermined position of the surface of the cyclic | annular intermediate part 120 so that it may be transmitted to the upper surface of the part 120. FIG. Accordingly, each piezoelectric element may be directly fixed to the surface of the annular intermediate portion 120, or may be indirectly fixed via some other member. In the embodiment described here, an upper electrode is formed on the upper surface of each piezoelectric element, and a lower electrode is formed on the lower surface. Each piezoelectric element is indirectly connected to the surface of the annular intermediate portion 120 via the lower electrode. In FIG. 2, the illustration of the upper electrode and the lower electrode is omitted because the drawing becomes complicated.

<<< §2. Deflection of each part of sensor according to basic embodiment >>>
Next, let us examine what kind of bending occurs in each portion of the annular intermediate portion 120 when a force in the direction of each coordinate axis acts on the weight body 210 of the sensor shown in FIG. Specifically, let us consider how the structure of the sensor deforms when a force in the direction of each coordinate axis acts on the center of gravity G of the weight body 210. First, the deformation state when the force + Fx in the X-axis positive direction is applied is shown in the side sectional view of FIG. 6, and the deformation state when the force -Fx in the negative direction of the X-axis is applied is shown in the side sectional view of FIG. Shown in Here, among the portions of the main body substrate 100, the inner portion 110 and the outer portion 130 have sufficient rigidity, whereas the thin annular intermediate portion 120 has flexibility. Therefore, a diagram assuming that the deformation is concentrated on the annular intermediate portion 120 is shown. Strictly speaking, the inner portion 110 and the outer portion 130 are slightly deformed. However, if the annular intermediate portion 120 is sufficiently thin, in practice, the deformation is substantially the annular intermediate portion 120. There is no problem considering that it concentrates on. For example, when the main body substrate 100 is formed of a silicon substrate, if the thickness of the entire substrate (the thickness of the inner portion 110 and the outer portion 130) is set to about 0.3 mm and the thickness of the annular intermediate portion 120 is set to about 10 μm, the deformation is It concentrates on the substantially annular intermediate part 120.

  Here, let's focus on the bending of each part along the X axis. In particular, attention is paid to the expansion and contraction in the longitudinal direction of the X-axis detection piezoresistive elements Px1 to Px4 shown in FIG. 6 and 7, each arrow described above the annular intermediate portion 120 indicates this stretched state. A pair of arrows pointing outward indicates that the region extends compared to a normal state (a state where no force is applied), and a pair of arrows pointing inward indicates that the region contracts compared to a normal state. ing.

  For example, as shown in FIG. 6, when a force + Fx in the positive direction of the X axis acts on the center of gravity G, the piezoresistive elements Px1 and Px3 contract and Px2 and Px4 expand. On the contrary, when the force -Fx in the negative direction of the X-axis acts, as shown in FIG. 7, the piezoresistive elements Px1 and Px3 expand and Px2 and Px4 contract. At this time, the piezoresistive elements Py1 to Py4 arranged on the Y axis are deformed to be twisted in the width direction, but are not significantly deformed in the longitudinal direction. The expansion and contraction of the piezoresistive elements Pz1 to Pz4 is substantially the same as the expansion and contraction of the piezoresistive elements Px1 to Px4.

  Next, let us consider a case where a force + Fy in the positive Y-axis direction and a force −Fy in the negative Y-axis direction are applied to the center of gravity G. As shown in FIG. 5, the X axis and the Y axis are orthogonal to each other, and the shape is exactly the same even if the main body substrate 100 is rotated by 90 ° about the origin O. Therefore, the deformation mode when the force related to the X-axis direction is applied can be applied as it is to the deformation mode when the force related to the Y-axis direction is applied. That is, the expansion and contraction of the piezoresistive elements Py1 to Py4 when the force related to the Y-axis direction is applied is the same as the expansion and contraction of the piezoresistive elements Px1 to Px4 when the force related to the X-axis direction is applied. Further, when a force related to the Y-axis direction is applied, the piezoresistive elements Px1 to Px4 arranged on the X-axis are deformed to be twisted with respect to the width direction, but are not significantly deformed with respect to the longitudinal direction. Similarly, the expansion and contraction of the piezoresistive elements Pz1 to Pz4 when a force in the Y-axis direction is applied is substantially the same as the expansion and contraction of the piezoresistive elements Px1 to Px4, and no significant deformation occurs in the longitudinal direction.

  Next, consider a case where a force in the Z-axis direction is applied to the center of gravity G. FIG. 8 is a side sectional view showing a deformed state when a force + Fz in the positive direction of the Z-axis is applied. As the weight body 210 moves upward, the piezoresistive elements Px2, Px3, Py2, Py3, Pz2, and Pz3 disposed in the inner vicinity region are extended, and the piezoresistive elements Px1 disposed in the outer vicinity region. , Px4, Py1, Py4, Pz1, Pz4 shrink. On the other hand, FIG. 9 is a side sectional view showing a deformed state when a force -Fz in the Z-axis negative direction is applied. When the weight body 10 moves downward, the piezoresistive elements Px2, Px3, Py2, Py3, Pz2, and Pz3 arranged in the inner vicinity area contract, and the piezoresistive elements Px1 arranged in the outer vicinity area. , Px4, Py1, Py4, Pz1, Pz4 extend.

  As shown in FIG. 2, since the gap dimensions d1, d2, and d3 are secured around the weight body 210, if the amount of displacement in each axial direction is within these dimension ranges, the weight The weight body 210 can be freely displaced, but if a further displacement is to be generated, the upper surface of the weight body 210 abuts on the lower surface of the outer portion 130, or the outer peripheral surface of the weight body 210 is the pedestal 220. The displacement is suppressed by abutting on the inner peripheral surface or the bottom surface of the weight body 210 abutting on the upper surface of the support substrate 300. That is, even if an excessive external force is applied to the weight body 210, the displacement generated in the weight body 210 is suppressed within a predetermined range. Such a structure is useful for preventing the support structure of the weight body 210 from being damaged by the action of an excessive external force. For example, if the gap dimensions d1, d2, and d3 are set to about 10 μm, it is possible to withstand an impact of about 3,000 to 10,000 G.

  Now, based on the examination results shown in FIG. 6 to FIG. 9, the stretched state in the longitudinal direction at each part of the upper surface of the annular intermediate part 120 when forces in the coordinate axis directions are applied to the weight body 210 of the sensor shown in FIG. 2. Are collectively shown in the top views of FIGS. That is, FIG. 10 is a top view showing a state in which an X-axis positive direction force + Fx is applied, FIG. 11 is a top view showing a state in which an X-axis negative direction force −Fx is applied, and FIG. 12 is a Y-axis positive direction force. FIG. 13 is a top view showing a state where a force −Fy in the Y-axis negative direction is applied, and FIG. 14 is a top view showing a state where a force + Fz in the Z-axis positive direction is applied. 15 is a top view showing a state in which a negative force -Fz in the Z-axis is applied.

  In either figure, a pair of arrows pointing outward indicates that the part extends compared to a normal state (a state where no force is applied), and a pair of arrows pointing inward indicates that the part is in a normal state. Compared to the shrinkage. In addition, the expansion / contraction considered here is an expansion / contraction about the direction (direction shown by the arrow) along the coordinate axis of each part to the last. Bars without arrows indicate that no significant expansion or contraction occurs in the direction along the bar. Moreover, the expansion / contraction result shown here is a result of expansion / contraction on the upper surface of the annular intermediate portion 120, and is not a result of expansion / contraction on the inside or the lower surface.

<<< §3. Detailed structure of piezoresistive element and piezoelectric element >>
FIG. 16 is an enlarged side sectional view of a portion where each piezoresistive element P (one of the twelve sets of piezoresistive elements Px1 to Px4, Py1 to Py4, Pz1 to Pz4 shown in FIG. 5) is formed. As described above, the piezoresistive element P is embedded in the upper surface layer portion of the main body substrate 100. In the embodiment shown here, the main body substrate 100 is constituted by an N-type silicon substrate, and the piezoresistive element P is constituted by a P-type impurity-containing layer formed on a part of the N-type silicon substrate. . Of course, the piezoresistive element can be constituted by an N-type impurity-containing layer formed in the surface layer portion of the P-type silicon substrate.

  In FIG. 16, the wiring extending from the terminals T1 and T2 is shown by lines, but this indicates that the wiring is formed between the left and right ends of the piezoresistive element P and the terminals T1 and T2. It is a thing. In practice, such a wiring layer is formed using a metal such as aluminum.

  The piezoresistive element P is an element having the property that the electrical resistance increases or decreases according to the mechanical expansion / contraction state. Therefore, in the example shown in FIG. When the element P expands and contracts in the longitudinal direction (left and right direction in the figure), the electrical resistance between the terminals T1 and T2 changes. As will be described later, acceleration detection is performed by electrically detecting this change in electrical resistance.

  On the other hand, FIG. 17 is an enlarged side cross-sectional view of a portion where the piezoelectric element F (one of the piezoelectric elements D1 to D4 and E1 to E4 shown in FIG. 1) is formed. As already described, the piezoelectric element F is fixed to the upper surface of the main body substrate 100. In the example shown in the figure, the piezoelectric element F has a plate shape, and the upper electrode UE is fixed to the upper surface thereof, and the lower electrode LE is fixed to the lower surface thereof. Since the lower surface of the lower electrode LE is fixed to the upper surface of the main substrate 100, the piezoelectric element F is eventually fixed to the upper surface of the main substrate 100 indirectly via the lower electrode LE. As a result, the bending (mechanical deformation) generated on the upper surface of the main body substrate 100 (annular intermediate portion 120) is transmitted to the piezoelectric element F. Conversely, the bending generated in the piezoelectric element F is the main body substrate 100 (annular intermediate portion). Transmitted to the upper surface of the portion 120).

  In the embodiment shown here, as described above, the main body substrate 100 is made of an N-type silicon substrate, and the piezoelectric element F is made of PZT (lead zirconate titanate) (such as aluminum nitride). Other piezoelectric elements may be used), and the upper electrode UE and the lower electrode LE are formed of a metal layer. In FIG. 17, wirings extending from the terminals U and L are indicated by lines. This is because wirings are connected between the terminal U and the upper electrode UE and between the terminal L and the lower electrode LE, respectively. This is done for the sake of convenience. Actually, such a wiring layer is formed using metal.

  In general, a piezoelectric element has a property that a voltage is generated when a stress is applied, and a stress is generated when a voltage is applied. The piezoelectric element F shown in FIG. 17 has a property that a voltage is generated between the upper electrode UE and the lower electrode LE when a stress for expanding and contracting in the horizontal direction (direction parallel to the upper surface of the main body substrate 100) is applied. . The polarity of the generated voltage depends on the direction of the applied stress (in the direction of stretching or contracting in the lateral direction), and the magnitude of the generated voltage depends on the magnitude of the applied stress. . The piezoelectric element F has a property of expanding and contracting in the horizontal direction in the figure when a voltage is applied between the upper electrode UE and the lower electrode LE. Whether to stretch or contract depends on the polarity of the applied voltage, and the amount of expansion / contraction deformation depends on the magnitude of the applied voltage.

<<< §4. Principle of acceleration detection >>>
Here, the principle of acceleration detection of the sensor according to the basic embodiment shown in FIGS. 1 and 2 will be described. As described above, a total of 12 sets of piezoresistive elements P are embedded in the upper surface of the annular intermediate portion 120 as shown in FIG. 5 and acted on the basis of the change in electrical resistance of these piezoresistive elements P. Acceleration is detected. Each of the piezoresistive elements P is an element made of the same material having the same size, and only the arrangement position thereof is different.

  FIG. 18 is a circuit diagram showing an example of an acceleration detection circuit used in this sensor. 18A is a circuit that detects the X-axis direction component αx of the applied acceleration, FIG. 18B is a circuit that detects the Y-axis direction component αy of the applied acceleration, and FIG. 18C is operated. This circuit detects the Z-axis direction component αz of acceleration. A set of piezoresistive elements in these circuits is composed of a piezoresistive element P shown in FIG. 16, and both terminals T1 and T2 shown in FIG. 16 correspond to black circles shown in each circuit diagram of FIG. . Each circuit includes a bridge circuit composed of four sets of piezoresistive elements P, and a constant voltage is always applied to each bridge circuit from the DC power supply 50.

  First, the bridge circuit shown in FIG. 18A is composed of four sets of piezoresistive elements Px1 to Px4 arranged on the X axis in FIG. 5, and the bridge voltage Vx is measured by a potentiometer 51. . In the state where no force is applied, the electric resistances of these four sets of piezoresistive elements P are equal to each other. Therefore, the bridge circuit maintains an equilibrium state, and the bridge voltage Vx measured by the potentiometer 51 becomes zero. However, when a force related to the X-axis direction acts on the weight body 210, the stretched state shown in FIG. 10 or FIG. 11 occurs. The piezoresistive element P is an element having the property that the electrical resistance increases or decreases according to the mechanical expansion / contraction state. Therefore, when the expansion / contraction state shown in FIG. 10 or FIG. 11 occurs, the bridge circuit shown in FIG. Thus, the bridge voltage Vx measured by the potentiometer 51 becomes a positive or negative value.

  In the bridge circuit shown in FIG. 18 (a), the pair of piezoresistive elements Px1 and Px3 constituting the opposite side have the same expansion / contraction state with respect to the action of the force in the X-axis direction (if one extends, the other extends, Similarly, if one side contracts, the other also contracts, and similarly, the pair of piezoresistive elements Px2 and Px4 forming another opposite side also have the same expansion / contraction state with respect to the action of the force in the X-axis direction. The bridge voltage Vx measured by the potentiometer 51 is a value indicating the direction and magnitude of the force with respect to the applied X-axis direction, and is a value indicating the X-axis direction component αx of the acceleration.

  When a force in the Y-axis direction is applied, as shown in FIGS. 12 and 13, significant expansion and contraction is not caused in the four sets of piezoresistive elements Px1 to Px4 constituting the bridge circuit shown in FIG. Since it does not occur, there is no significant variation in the bridge voltage Vx. On the other hand, when a force related to the Z-axis direction is applied, as shown in FIGS. 14 and 15, the four piezoresistive elements Px1 to Px4 constituting the bridge circuit shown in FIG. Expansion and contraction will occur. However, the pair of piezoresistive elements Px1 and Px3 constituting the opposite sides of the bridge circuit have a relationship of taking a stretched state opposite to the action of the force in the Z-axis direction (if one stretches, the other shrinks and one shrinks). Similarly, the pair of piezoresistive elements Px2 and Px4 constituting another opposite side are also in a relationship of taking expansion and contraction that is opposite to the action of force in the Z-axis direction. Variations in the bridge voltage Vx due to the action of force in the direction are canceled out. As a result, the bridge circuit shown in FIG. 18A can independently detect only the X-axis direction component αx of the applied acceleration.

  On the other hand, the bridge circuit shown in FIG. 18 (b) is composed of four sets of piezoresistive elements Py1 to Py4 arranged on the Y axis in FIG. 5, and the bridge voltage Vy is measured by a potentiometer 52. . In the state where no force is applied, the electric resistances of these four sets of piezoresistive elements P are equal to each other. Therefore, the bridge circuit maintains an equilibrium state, and the bridge voltage Vy measured by the potentiometer 52 becomes zero. However, when a force in the Y-axis direction acts on the weight body 210, the expansion / contraction state shown in FIG. 12 or FIG. 13 occurs, and the equilibrium state of the bridge circuit is lost. Eventually, the bridge voltage Vy measured by the potentiometer 52 becomes a value indicating the Y-axis direction component αy of acceleration.

  In the case of the bridge circuit shown in FIG. 18 (b), when a force in the X-axis direction is applied, no significant fluctuation occurs in the bridge voltage Vy. In addition, when a force related to the Z-axis direction is applied, the pair of piezoresistive elements that constitute the opposite side are in a contradictory expansion / contraction state, so that fluctuations in the bridge voltage Vy due to the action of the force related to the Z-axis direction are canceled out. End up. Therefore, the bridge circuit shown in FIG. 18 (b) can independently detect only the Y-axis direction component αy of the applied acceleration.

  Further, the bridge circuit shown in FIG. 18 (c) is composed of four sets of piezoresistive elements Pz1 to Pz4 arranged on the Xa axis or Xb axis of FIG. Measured. In the state where no force is applied, the electric resistances of these four sets of piezoresistive elements P are equal to each other. Therefore, the bridge circuit maintains an equilibrium state, and the bridge voltage Vz measured by the potentiometer 53 becomes zero. However, when a force in the Z-axis direction is applied to the weight body 210, the stretched state shown in FIG. 14 or FIG. 15 occurs, and the balanced state of the bridge circuit is lost. Eventually, the bridge voltage Vz measured by the potentiometer 53 becomes a value indicating the Z-axis direction component αz of acceleration.

  In the case of the bridge circuit shown in FIG. 18 (c), the pair of piezoresistive elements constituting the opposite side is either a combination of elements arranged in the inner vicinity area, or both of the elements arranged in the outer vicinity area. It is a combination. Therefore, when a force related to the Z-axis direction is applied, the pair of piezoresistive elements constituting the opposite side take the same expansion / contraction state, and the bridge voltage Vz varies, but the force related to the X-axis direction or the Y-axis direction. When this occurs, the pair of piezoresistive elements constituting the opposite sides take opposite stretched states, so that the fluctuation in the bridge voltage Vz due to the action of the force in the X-axis direction or the Y-axis direction is canceled out. Therefore, the bridge circuit shown in FIG. 18 (c) can independently detect only the Z-axis direction component αz of the applied acceleration.

  Eventually, the acceleration detection circuit used in the sensor according to this basic embodiment uses the first X-axis detection piezoresistive element Px1 and the third X-axis detection piezoresistive element Px3 as the first opposite side, and the second The acceleration αx acting in the X-axis direction is detected based on the bridge voltage Vx of the bridge circuit having the X-axis detection piezoresistive element Px2 and the fourth X-axis detection piezoresistive element Px4 as the second opposite side, The first Y-axis detecting piezoresistive element Py1 and the third Y-axis detecting piezoresistive element Py3 are the first opposite sides, and the second Y-axis detecting piezoresistive element Py2 and the fourth Y-axis detecting piezoresistive element are used. Based on the bridge voltage Vy of the bridge circuit having the resistance element Py4 as the second opposite side, the acceleration αy acting in the Y-axis direction is detected, and the first Z-axis detection piezoresistance element Pz1 and the fourth Z-axis detection are detected. The bridge voltage Vz of the bridge circuit having the outgoing piezoresistive element Pz4 as the first opposite side and the second Z-axis detecting piezoresistive element Pz2 and the third Z-axis detecting piezoresistive element Pz3 as the second opposite side. Based on this, the acceleration αz acting in the Z-axis direction is detected.

  As described in §1, the arrangement of the four sets of piezoresistive elements used for detecting the force in the Z-axis direction is not limited to the arrangement shown in FIG. 5, and the piezoresistive elements Pz1 and Pz4 are It is only necessary to arrange the piezoresistive elements Pz2 and Pz3 at arbitrary positions in the outer vicinity area (in order to increase sensitivity, the direction from the origin O to the radial direction is preferably the longitudinal direction). Is preferred). This is because, when a force + Fz in the positive direction of the Z-axis is applied, as shown in FIG. 14, a force extending in a radial direction from the origin O is applied to the upper surface of the inner vicinity region, and When a force contracting in the radial direction from the origin O is applied, and conversely, when a force -Fz in the negative Z-axis direction is applied, as shown in FIG. This is because a force contracting in the direction is applied, and a force extending in the radial direction from the origin O is applied to the upper surface of the outer vicinity region.

<<< §5. Principle of angular velocity detection >>>
Next, the principle of angular velocity detection of the sensor according to the basic embodiment shown in FIGS. 1 and 2 will be described. As already described, a total of eight sets of piezoelectric elements are arranged on the upper surface of the annular intermediate portion 120 as shown in FIG. Each piezoelectric element is an element having a physically identical configuration, but is slightly different in size and arrangement (all have the same thickness). That is, the four sets of piezoelectric elements D1 to D4 arranged in the inner vicinity region are piezoelectric elements having the same shape and size, and only the arrangement positions thereof are different. Similarly, the four sets of piezoelectric elements E1 to E4 arranged in the outer vicinity region are also piezoelectric elements having the same shape and size, and only their arrangement positions are different. Further, when the four sets of piezoelectric elements D1 to D4 and the four sets of piezoelectric elements E1 to E4 are compared, the shape and size are different, and the latter has a larger planar area. This is because the outer vicinity region has a larger area than the inner vicinity region.

  As can be seen from the top view of FIG. 1, each piezoelectric element is arranged on the X axis or the Y axis, and the shape thereof is line-symmetric with respect to the arrangement axis. Further, since the entire arrangement pattern of each piezoelectric element is also line symmetric with respect to the X axis and the Y axis, the contour pattern of the piezoelectric element shown in FIG. 1 is eventually symmetrical with respect to both the X axis and the Y axis. Have. Such symmetry is important for the convenience of driving a weight body and force detection described later.

  Here, in consideration of the use of each piezoelectric element, the piezoelectric element used for detecting the force applied to the weight body 210 is called a detection piezoelectric element D, and the piezoelectric element used for driving the weight body 210. Is called a driving piezoelectric element E. Further, when the detection piezoelectric element D and the drive piezoelectric element E are referred to without distinction, they are simply referred to as “piezoelectric elements F”. The detailed structure of the piezoelectric element F is as shown in FIG. 17, and actually, the upper electrode UE is fixed to the upper surface and the lower electrode LE is fixed to the lower surface.

  As described above, the piezoelectric element F has a property that a voltage is generated when a stress is applied, and a stress is generated when a voltage is applied. By utilizing such a property of the piezoelectric element F, the weight body 210 can be driven. That is, if an alternating current signal is supplied to the driving piezoelectric elements E1 to E4 and the annular intermediate portion 120 is periodically deformed, the weight body 210 can be caused to periodically move.

  For example, a voltage having a first polarity is applied between the upper and lower electrodes of the driving piezoelectric element E1 shown in FIG. 1 so as to be contracted in a direction along the XY plane, and the driving piezoelectric element E2 is If a voltage having the second polarity is applied between both electrodes and is deformed so as to extend in the direction along the XY plane, a deformation mode as shown in FIG. 6 is obtained. The center of gravity G of 210 moves in the positive direction of the X axis. Further, if the polarity of the voltage applied to each of the driving piezoelectric elements E1 and E2 is reversed, a deformation mode as shown in FIG. 7 can be obtained, and the gravity center G of the weight body 210 moves in the negative direction of the X axis. To do.

  Eventually, AC drive signals S1 and S2 (a pair of sine wave signals having opposite phases to each other) as shown in FIG. 19 are prepared, and the lower electrode LE of each drive piezoelectric element is kept at the ground level, and the drive shown in FIG. If the drive signal S1 is supplied to the upper electrode UE of the piezoelectric element E1 and the drive signal S2 is supplied to the upper electrode UE of the drive piezoelectric element E2, the center of gravity G of the weight body 210 is simply oscillated in the X-axis direction. Can be made. For example, when a positive voltage is applied to the upper electrode UE, the piezoelectric element expands, and when a negative voltage is applied, the piezoelectric element contracts. (Depending on the piezoelectric element, the reverse characteristic may be present. In the specification, for the sake of convenience, it is assumed that the piezoelectric element having the characteristics as described above is used), and in the periods t1 and t3, an action is performed to move the weight body 210 in the negative direction of the X axis. At t2 and t4, an action for moving the weight body 210 in the X-axis positive direction is performed.

  Similarly, if the center of gravity G of the weight body 210 is simply oscillated in the Y-axis direction, the lower electrode LE of each driving piezoelectric element is kept at the ground level, and the upper electrode UE of the driving piezoelectric element E3 shown in FIG. Is supplied with the drive signal S1, and the drive signal S2 may be supplied to the upper electrode UE of the drive piezoelectric element E4. Further, if the center of gravity G of the weight body 210 is simply vibrated in the Z-axis direction, the deformation mode shown in FIG. 14 and the deformation mode shown in FIG. 15 may be alternately repeated. Therefore, the lower electrode LE of each driving piezoelectric element may be kept at the ground level, and the driving signal S1 (or driving signal S2) may be supplied to the upper electrode UE of each piezoelectric element E1 to E4. Thus, by supplying a specific drive signal to a specific drive piezoelectric element E, the center of gravity G of the weight body 210 can be oscillated in the X-axis, Y-axis, or Z-axis direction. .

  Further, if four kinds of drive signals SS1 to SS4 (sine wave signals whose phases are shifted by π / 2) as shown in FIG. 20 are prepared, the center of gravity G of the weight body 210 can be circularly moved. . For example, if the center of gravity G is circularly moved in a plane parallel to the XY plane, the lower electrodes LE of the driving piezoelectric elements E1 to E4 are kept at the ground level, and the driving signals SS1 to SS4 are respectively applied to the upper electrodes UE. What is necessary is just to supply. Specifically, the drive signal SS1 is given to the upper electrode UE of the piezoelectric element E1, the drive signal SS2 is given to the upper electrode UE of the piezoelectric element E3, and the drive signal SS3 is given to the upper electrode UE of the piezoelectric element E2. The drive signal SS4 may be given to the upper electrode UE of the piezoelectric element E4. In the period t1, an action for moving the weight body 210 in the negative direction of the X axis is performed, and in a transition period of the periods t1 to t2, an action for moving the weight body 210 in the negative direction of the Y axis is performed. In the period t2, an action for moving the weight body 210 in the positive direction of the X axis is performed, and in a transition period of the periods t2 to t3, an action for moving the weight body 210 in the positive direction of the Y axis is performed. I ... and so on.

  In this way, if a drive signal supplied to each of the driving piezoelectric elements E1 to E4 is appropriately selected, the center of gravity G can be circularly moved in the XZ plane or the YZ plane. In the above description, the example in which the lower electrodes LE of the driving piezoelectric elements E1 to E4 are kept at a common ground level and individual driving signals are supplied to the individual upper electrodes UE has been described. The upper electrodes UE of the driving piezoelectric elements E1 to E4 may be kept at a common ground level, and individual driving signals may be supplied to the individual lower electrodes UL. 19 and 20 show an example in which a sine wave signal is used as a drive signal. However, since the signal supplied to the drive piezoelectric element may be an AC signal, for example, a rectangular wave signal is used. Is also possible.

  Next, functions of the detection piezoelectric elements D1 to D4 will be described. Since electrical signals based on the expansion and contraction of each part are generated in the detection piezoelectric elements D1 to D4, by using this, it is possible to detect the force in each axial direction acting on the weight body 210.

  For example, when a force + Fx in the positive direction of the X-axis acts on the weight body 210, expansion and contraction as shown in FIG. Further, when a force −Fx in the negative X-axis direction is applied, expansion and contraction as shown in FIG. In either case, the expansion and contraction states of the detection piezoelectric elements D1 and D2 are opposite to each other, so that the polarity of the electrical signal generated in the detection piezoelectric element D1 is opposite to the polarity of the electrical signal generated in the detection piezoelectric element D2. Become. Therefore, if the difference between the two is obtained, the X-axis direction component of the force acting on the weight body 210 can be detected (the sign of the difference indicates the direction of the force, and the absolute value of the difference indicates the magnitude of the force. ).

  Further, when a force + Fy in the Y-axis positive direction acts on the weight body 210, expansion and contraction as shown in FIG. 12 occurs on the upper surface of the annular intermediate portion 120, and a force -Fy in the Y-axis negative direction acts. The upper and lower surfaces of the annular intermediate portion 120 expand and contract as shown in FIG. In either case, the expansion and contraction states of the detection piezoelectric elements D3 and D4 are opposite to each other, so that the polarity of the electric signal generated in the detection piezoelectric element D3 is opposite to the polarity of the electric signal generated in the detection piezoelectric element D4. Become. Therefore, if the difference between the two is obtained, the Y-axis direction component of the force acting on the weight body 210 can be detected (the sign of the difference indicates the direction of the force, and the absolute value of the difference indicates the magnitude of the force. ).

  On the other hand, when a force + Fz in the positive direction of the Z axis acts on the weight body 210, expansion and contraction as shown in FIG. 14 occurs on the upper surface of the annular intermediate portion 120, and a force −Fz in the negative direction of the Z axis acts. The expansion and contraction as shown in FIG. In either case, the expansion and contraction states of the detection piezoelectric elements D1 to D4 are the same, so the polarities of the electrical signals generated in the detection piezoelectric elements D1 to D4 are the same. Therefore, for example, if the sum of the electrical signal generated in the piezoelectric element D1 and the electrical signal generated in the piezoelectric element D2 or the sum of the electrical signal generated in the piezoelectric element D3 and the electrical signal generated in the piezoelectric element D4 is obtained (total piezoelectricity). The sum of the electrical signals generated in the elements D1 to D4 may be obtained), and the Z-axis direction component of the force acting on the weight body 210 can be detected (the sign of the sum indicates the direction of the force, Absolute value indicates the magnitude of the force).

  In this way, the force in the X-axis direction acting on the weight body 210 is detected based on the difference between the signals from the piezoelectric elements D1 and D2, and Y acting on the weight body 210 based on the difference between the signals from the piezoelectric elements D3 and D4. If the axial force is detected and the Z-axis direction force acting on the weight body 210 is detected by the sum of signals from the piezoelectric elements D1, D2 (or D3, D4), interference of other axial force components is suppressed. The detected value can be obtained.

  For example, when a force in the Y-axis direction is applied to the weight body 210, expansion and contraction as shown in FIG. That is, axial expansion and contraction occurs on the Y axis, but no axial expansion and contraction occurs on the X axis. However, as shown in FIG. 1, since the piezoelectric elements D1 and D2 are elements that also spread in the Y-axis direction, they are affected by expansion and contraction in the Y-axis direction, and force in the Y-axis direction Even when this occurs, electric charges are generated for each portion. However, since the shapes of the piezoelectric elements D1 and D2 are line symmetric with respect to the X axis, the charges generated in the upper half region and the charges generated in the lower half of the symmetry axis (X axis) cancel each other, and the piezoelectric element D1 The output value output in total from the output value and the output value output in total from the piezoelectric element D2 are zero. Therefore, if the force in the X-axis direction applied to the weight body 210 is detected based on the difference between the signals from the piezoelectric elements D1 and D2, the force component in the Y-axis direction is not mixed with the detected value.

  In addition, when a force in the Z-axis direction is applied to the weight body 210, expansion and contraction as shown in FIG. However, in this case, since the output value output from the piezoelectric element D1 and the output value output from the piezoelectric element D2 are equal, the X axis acting on the weight body 210 due to the difference between the signals from the piezoelectric elements D1 and D2. If the force in the direction is detected, the force component in the Z-axis direction is not mixed with the detected value.

  After all, if the force in the X-axis direction applied to the weight body 210 is detected by the difference between the signals from the piezoelectric elements D1 and D2, the detected value affects the force in the Y-axis direction and the force in the Z-axis direction. The correct value will not be. For the same reason, if the Y-axis direction force acting on the weight body 210 is detected by the difference in the signals from the piezoelectric elements D3 and D4, the detected value is the X-axis direction force or the Z-axis direction force. The correct value is not affected by force. Further, if the Z-axis direction force acting on the weight body 210 is detected by the sum of the signals from the piezoelectric elements D1, D2 (or D3, D4), the X-axis direction force and the Y-axis direction force can be detected. Even if a force is applied, it is canceled out by taking the sum, so that the detected value is a correct value that is not influenced by the force in the X-axis direction or the force in the Y-axis direction.

  By the way, when an object is moving at a velocity V in the direction of the first coordinate axis in the three-dimensional orthogonal coordinate system, when an angular velocity ω around the second coordinate axis acts on this object, The Coriolis force Fc acts in the coordinate axis direction, and the angular velocity ω becomes a value proportional to Fc / V. The sensor according to the present invention has a function of detecting an angular velocity around a desired coordinate axis using this principle.

  For example, if the weight body 210 is simply vibrated in the X-axis direction by the above-described method, and the Y-axis direction force (Coriolis force) Fc acting on the weight body 210 is detected by the above-described method in that state. Based on the detected value, the angular velocity ωz around the Z-axis acting on the weight body 210 can be obtained. In this case, for example, if it is determined that “the force Fc is detected at the moment when the center of gravity G of the weight body 210 passes the center position (YZ plane) of the simple vibration”, the weight at the measurement timing is determined. Since the velocity V in the X-axis direction of the body 210 is always constant (maximum velocity of simple vibration), the detection value of the force Fc can be handled as an amount proportional to the angular velocity ωz as it is.

  Similarly, the angular velocity ωy around the Y axis can be detected by detecting the Coriolis force Fc acting in the Z axis direction in a state where the weight body 210 is simply vibrated in the X axis direction. Alternatively, the angular velocity ωx around the X axis can be detected by detecting the Coriolis force Fc acting in the Z axis direction in a state where the weight body 210 is simply vibrated in the Y axis direction. In short, in the sensor according to this basic embodiment, the weight body 210 can be moved in desired directions of the X axis, the Y axis, and the Z axis, and in this state, the X axis acting on the weight body 210, Since the Coriolis force in the Y-axis and Z-axis directions can be detected, the angular velocities around the X-axis, Y-axis, and Z-axis can be detected by appropriately combining the drive axis and the detection axis.

<<< §6. Three-dimensional angular velocity detection >>>
In §5 described above, the principle of detecting the angular velocity is described, but here, the weight body 210 is moved in a circular motion, whereby the angular velocity ωx around the X axis, the angular velocity ωy around the Y axis, and the angular velocity ωz around the Z axis are calculated. A specific method of three-dimensional angular velocity detection capable of detecting all will be described.

  As described in §5, if four drive signals SS1 to SS4 (sine wave signals whose phases are shifted by π / 2) as shown in FIG. 20 are used, the weight body 210 is placed in a plane parallel to the XY plane. You can make a circular motion with. Here, a method of detecting the three-dimensional angular velocities ωx, ωy, and ωz in a state where the weight body 210 performs such a circular motion will be considered.

  Here, for convenience of explanation, in the XYZ three-dimensional coordinate system as shown in FIG. 21, consider the case where the gravity center G of the weight body is circularly moving in the XY plane (actually, the gravity center G of the weight body is Although the circular motion is performed in a plane parallel to the XY plane, it is assumed here that the motion of the center of gravity G is a circular motion on the XY plane for convenience. A circular orbit H shown in FIG. 21 is a circle drawn on the XY plane with the origin O as the center, and corresponds to the motion locus of this weight body.

  In such a circular motion, attention is paid to the moment when the center of gravity G passes through the points Q1 and Q3 shown in the figure. Point Q1 is a position at the moment when the center of gravity G passes through the XZ plane with a velocity Vy directed in the positive Y-axis direction, and point Q3 is an XZ plane with a velocity −Vy where the center of gravity G is directed in the negative Y-axis direction. It is the position at the moment of passing. At any position, the weight body 210 is moving in the Y-axis direction, and if the Coriolis force acting in the X-axis direction at this moment is detected, the angular velocity around the Z-axis can be obtained. If the Coriolis force acting in the Z-axis direction at this moment is detected, the angular velocity around the X-axis can be obtained.

  Similarly, attention is paid to the moment when the center of gravity G passes through the illustrated points Q2 and Q4 in such a circular motion. Point Q2 is the momentary position when the center of gravity G passes through the YZ plane with a velocity −Vx directed in the negative X-axis direction, and point Q4 is the YZ plane with velocity Vx where the center of gravity G faces in the positive X-axis direction. It is the position at the moment of passing. At any position, the weight body 210 moves in the X-axis direction. Therefore, if the Coriolis force acting in the Y-axis direction is detected at this moment, the angular velocity around the Z-axis can be obtained. If the Coriolis force acting in the Z-axis direction at this moment is detected, the angular velocity around the Y-axis can be obtained.

  As already described, the force in the direction of each coordinate axis acting on the weight body 210 can be detected using each of the detection piezoelectric elements D1 to D4. Consider a case where a detection circuit as shown in FIG. 22 is prepared. The upper circuit in FIG. 22 is a circuit that detects the X-axis direction component of the applied force, and the lower circuit is a circuit that detects the Z-axis direction component of the applied force. In this circuit, the lower electrode LE of each detection piezoelectric element D is maintained at a common ground level, and the result of analog calculation based on the voltage value generated at each upper electrode UE is output to the terminals Tx and Tz.

  That is, the circuit shown in the upper part of FIG. 22 is an arithmetic circuit for the detection piezoelectric elements D1 and D2 on the X axis shown in FIG. 1, and the voltage value of the upper electrode D1U of the detection piezoelectric element D1 and the detection piezoelectric element. It is comprised by the calculator 61 which calculates | requires the difference with the voltage value of upper electrode D2U of D2. The voltage value indicating the obtained difference value is output to the output terminal Tx as a detected value of the X-axis direction component of the force acting on the weight body 210. Similarly, the circuit shown in the lower part of FIG. 22 is an arithmetic circuit for the detection piezoelectric elements D3 and D4 on the Y axis shown in FIG. 1, and the voltage value of the upper electrode D3U of the detection piezoelectric element D3 and the detection piezoelectric element. It is comprised by the calculator 62 which calculates | requires the sum with the voltage value of the upper electrode D4U of the element D4. The voltage value indicating the obtained sum value is output to the output terminal Tz as a detected value of the Z-axis direction component of the force acting on the weight body 210.

  If the angular velocity detection circuit shown in FIG. 22 is used, the three-dimensional angular velocities ωx, ωy, and ωz can be detected at the following timing. That is, in the diagram shown in FIG. 21, output is performed at the moment when the center of gravity G of the weight body 210 passes through the points Q1 and Q3 (timing when the weight body moves in the Y-axis direction and passes through the XZ plane). The detected value of the force of the X-axis direction component output to the terminal Tx is a value corresponding to the angular velocity ωz around the Z-axis, and the detected value of the force of the Z-axis direction component output to the output terminal Tz is the X-axis It becomes a value according to the surrounding angular velocity ωx. In addition, Z is output to the output terminal Tz at the moment when the center of gravity G of the weight body 210 passes through the points Q2 and Q4 (timing when the weight body moves in the X-axis direction and passes through the YZ plane). The detected value of the axial component force is a value corresponding to the angular velocity ωy about the Y axis.

  Thus, the three-dimensional angular velocities ωx, ωy, and ωz can be detected by extracting the output values of the output terminals Tx and Tz at a predetermined timing. Note that the timing at which the center of gravity G of the weight body 210 passes through the points Q1, Q2, Q3, and Q4 can be determined based on the phases of the drive signals SS1 to SS4 shown in FIG. Actually, a time delay inherent in the system composed of the physical structure occurs between the time when the driving signals SS1 to SS4 are supplied and the weight body 210 performs a predetermined motion. In practice, it is preferable to determine an appropriate timing by actually measuring the motion of the weight body 210.

  After all, the angular velocity detection circuit based on the above-described detection principle supplies the alternating current signal whose phase is shifted by π / 2 to each of the driving piezoelectric elements E1 to E4, so that the weight body 210 is a plane parallel to the XY plane. Based on the difference between the signal generated in the first detection piezoelectric element D1 and the signal generated in the second detection piezoelectric element D2 when the weight body 210 passes through the XZ plane while being circularly moved in the Z axis. A surrounding angular velocity ωz is detected, and X is determined based on the sum of a signal generated in the third detection piezoelectric element D3 and a signal generated in the fourth detection piezoelectric element D4 when the weight body 210 passes through the XZ plane. The angular velocity ωx around the axis is detected, and Y is determined based on the sum of the signal generated in the third detection piezoelectric element D3 and the signal generated in the fourth detection piezoelectric element D4 when the weight passes through the YZ plane. The angular velocity ωy around the axis It will be out.

  In the example described above, four sets of driving signals SS1 to SS4 shown in FIG. 20 are supplied to the four sets of driving piezoelectric elements E1 to E4, and the weight body 210 is circularly moved in a plane parallel to the XY plane. As an example, the three-dimensional angular velocities ωx, ωy, and ωz can be detected by circularly moving the weight body 210 in the XZ plane or the YZ plane. For example, when circular motion is performed in the XZ plane, two types of drive signals SSS1 and SSS2 as shown in FIG. 23 are prepared. The phase of the drive signal SSS2 is delayed by π / 2 with respect to the drive signal SSS1.

  Here, the drive signal SSS1 is supplied to the drive piezoelectric element E1, and the drive signal SSS2 is supplied to the drive piezoelectric element E2. Specifically, the lower electrode LE of the driving piezoelectric elements E1 and E2 is kept at the ground level, the driving signal SSS1 is given to the upper electrode UE of the piezoelectric element E1, and the driving signal SSS2 is given to the upper electrode UE of the piezoelectric element E2. Give it. In the driving method described here, the piezoelectric elements E3 and E4 are not used. In a period t1 on the time axis in FIG. 23, an action for moving the weight body 210 in the negative direction of the X axis is performed. Moreover, focusing on the latter half of the period t1, since the drive signals SSS1 and SSS2 both show positive values, both the piezoelectric elements E1 and E2 are deformed in the extending direction, and as shown in FIG. An action for moving the weight body 210 in the negative Z-axis direction is performed. In the period t2, an action for moving the weight body 210 in the positive direction of the X-axis is performed. When attention is paid to the latter half of the period t2, the drive signals SSS1, SSS2 both show negative values. Therefore, both the piezoelectric elements E1 and E2 are deformed in the contracting direction, and an action for moving the weight body 210 in the positive Z-axis direction is performed as shown in FIG.

  Thus, the weight body 210 moves circularly in the XZ plane. Similarly, when the drive signals SSS1 and SSS2 are supplied to the piezoelectric elements E3 and E4, the weight body 210 moves circularly in the YZ plane. Thus, even if the circular motion plane of the weight body 210 is the XZ plane or the YZ plane, the basic principle of angular velocity detection shown in FIG. 21 is the same. For example, when the weight body 210 is circularly moved in the XZ plane, a detection circuit as shown in FIG. 24 may be prepared.

  The upper circuit in FIG. 24 is a circuit that detects the X-axis direction component of the applied force, and the lower circuit is a circuit that detects the Y-axis direction component of the applied force. In this circuit, the lower electrode LE of each detection piezoelectric element D is maintained at a common ground level, and the result of analog calculation based on the voltage value generated in each upper electrode UE is output to the terminals Tx and Ty.

  That is, the circuit shown in the upper part of FIG. 24 is substantially the same as the circuit shown in the upper part of FIG. 22, and is an arithmetic circuit for the detection piezoelectric elements D1 and D2 on the X axis shown in FIG. The calculator 63 is configured to obtain a difference between the voltage value of the upper electrode D1U of the piezoelectric element D1 and the voltage value of the upper electrode D2U of the detecting piezoelectric element D2. The voltage value indicating the obtained difference value is output to the output terminal Tx as a detected value of the X-axis direction component of the force acting on the weight body 210. Similarly, the circuit shown in the lower part of FIG. 24 is an arithmetic circuit for the detection piezoelectric elements D3 and D4 on the Y axis shown in FIG. 1, and the voltage value of the upper electrode D3U of the detection piezoelectric element D3 and the detection piezoelectric element. It is comprised by the calculator 64 which calculates | requires the difference with the voltage value of the upper electrode D4U of the element D4. The voltage value indicating the obtained difference value is output to the output terminal Ty as the detected value of the Y-axis direction component of the force acting on the weight body 210.

  If the circuit shown in FIG. 24 is used, the three-dimensional angular velocities ωx, ωy, and ωz can be detected by the following method. That is, by supplying AC signals SSS1 and SSS2 whose phases are shifted from each other by π / 2 to the first driving piezoelectric element E1 and the second driving piezoelectric element E2, as shown in FIG. While the weight body 210 is circularly moved in the XZ plane, the signal generated in the first detection piezoelectric element D1 and the second detection piezoelectric element D2 when the weight body 210 moves in the Z-axis direction. The angular velocity ωy around the Y axis is detected based on the difference from the generated signal (the detected value of the force in the X axis direction output to the output terminal Tx in FIG. 24), and the weight body 210 similarly moves in the Z axis direction. The difference between the signal generated in the third detection piezoelectric element D3 and the signal generated in the fourth detection piezoelectric element D4 at the time (the detected value of the force in the Y-axis direction output to the output terminal Ty in FIG. 24) Detects angular velocity ωx around the X axis based on The difference between the signal generated in the third detection piezoelectric element D3 and the signal generated in the fourth detection piezoelectric element D4 when the weight body 210 moves in the X-axis direction (at the output terminal Ty in FIG. 24). The angular velocity ωz around the Z axis may be detected based on the output detection value of the force in the Y axis direction.

<<< §7. Example of configuration including wiring of piezoresistive element and piezoelectric element >>
As already described in §3, the piezoresistive element P used in the sensor according to the basic embodiment of the present invention is a surface layer of the main body substrate 100 made of an N-type silicon substrate, as shown in the enlarged side sectional view of FIG. It consists of a P-type impurity content layer formed in the part. Further, the piezoelectric element F used in the sensor according to the basic embodiment of the present invention is a plate-like element disposed on the upper surface of the main body substrate 100 made of an N-type silicon substrate, as shown in the enlarged side sectional view of FIG. It consists of PZT.

  However, as can be seen from the top view of FIG. 1, the arrangement of the piezoresistive elements overlaps the arrangement of the piezoelectric elements in a plane. This is because the stress on the annular intermediate portion 120 tends to concentrate, that is, the inner vicinity region (the region immediately outside the inner contour line C1 shown in FIG. 5) and the outer vicinity region (the outer contour line C2 shown in FIG. 5). This is because each piezoresistive element and each piezoelectric element are arranged in the region closest to the inside to increase detection sensitivity. Of course, when viewed three-dimensionally, as shown in the side sectional view of FIG. 2, the piezoresistive element P is embedded in the upper layer of the main body substrate 100, and the piezoelectric element is formed thereabove. It will be. In addition, the piezoresistive element P requires wiring to both ends thereof, and the piezoelectric element needs to form the upper electrode UE and the lower electrode LE and also have wiring to these electrodes. Furthermore, if necessary, an insulating layer for insulating the electrodes and wiring from each other is also required. Therefore, hereinafter, a configuration example including wiring of the piezoresistive element and the piezoelectric element will be described.

  FIG. 25 is an enlarged side cross-sectional view of the overlapping formation portion of the piezoresistive element and the piezoelectric element in the vicinity of the upper surface of the main body substrate 100 of the sensor shown in FIGS. 1 and 2. As described above, the main body substrate 100 is composed of an N-type silicon substrate, and the piezoresistive element P is composed of a P-type impurity-containing layer formed on the surface layer portion of the N-type silicon substrate. As illustrated, insulating layers 511, 512, and 513 (for example, a silicon oxide film or a silicon nitride film) are formed on the upper surface of the main body substrate 100. The wiring layer 521 formed on the insulating layer 511 and the wiring layer 522 formed on the insulating layer 512 are layers (for example, aluminum layers) for wiring to both ends of the piezoresistive element P. Yes, and used for wiring to the terminals T1 and T2.

The common metal layer LE ^* formed on the upper surface of the insulating layer 513 functions as a lower electrode used in common for all the piezoelectric elements F, and individual piezoelectric layers are formed at predetermined positions on the upper surface of the common metal layer LE ^*. An element F (for example, PZT) is formed, and an individual upper electrode UE is formed on the upper surface thereof. As described above, the piezoelectric element F and the upper electrode UE are individually arranged to form a total of eight sets of piezoelectric elements D1 to D4 and E1 to E4 shown in FIG. Instead of forming an individual electrode LE for each individual piezoelectric element F, the electrode LE is replaced by one common metal layer LE ^* .

If such a configuration is adopted, as described in the principle of angular velocity detection in §5, wiring can be omitted when detection is performed by connecting all the lower electrodes LE to a common ground potential. So convenient. In the example of FIG. 25, wiring to all the lower electrodes LE is completed by connecting the terminal L ^* of the common metal layer to the ground potential. In short, the advantage of simplifying the wiring can be obtained by physically configuring the lower electrodes of the plurality of piezoelectric elements with a single common conductive layer (common metal layer LE ^* ). Of course, the individual metal layers may be formed only in the regions below the individual piezoelectric elements F without using the common metal layer LE ^* .

On the other hand, FIG. 26 is an enlarged side sectional view of a portion where only the piezoelectric element is formed in the vicinity of the upper surface of the main body substrate 100 of the sensor shown in FIGS. An insulating layer 513 (for example, a silicon oxide film or a silicon nitride film) is formed on the upper surface of the main body substrate 100, and the layer structure thereon is exactly the same as that shown in FIG. In other words, the insulating layers 511, 512, and 513 shown in FIG. 25 and the insulating layer 513 shown in FIG. 26 are substantially the same layer, and the wiring layers 521 and 522 shown in FIG. Wiring embedded in the insulating layer. Further, the same layer in the common metal layer LE ^* is also substantially shown in a common metal layer LE ^* and 26 shown in FIG. 25.

  Thus, in the embodiment described here, the lower electrode LE is formed on the lower surface of each piezoelectric element, and the upper electrode UE is formed on the upper surface, and the lower surface of the lower electrode LE of each piezoelectric element is the annular intermediate portion 120. It is fixed to the upper surface of the insulating layer 513 with an insulating layer 513 interposed therebetween. As described above, the angular velocity detection circuit applies an AC voltage between the upper electrode UE and the lower electrode LE of the driving piezoelectric elements E1 to E4 to cause the weight body 120 to generate periodic motion. The angular velocity acting on the basis of the alternating voltage generated between the upper electrode and the lower electrode of the detecting piezoelectric elements D1 to D4 is detected.

Since both the piezoresistive element and the piezoelectric element are disposed in the annular intermediate portion 120, the insulating layer 513 and the common metal layer LE ^* are theoretically formed only on the upper surface of the annular intermediate portion 120. It is enough. However, practically, if the structure in which the insulating layer 513 and the common metal layer LE ^* are formed on the entire upper surface of the main body substrate 100, the manufacturing process can be simplified. Therefore, practically, first, after performing a process of embedding 12 sets of piezoresistive elements P on the upper surface of the main body substrate 100 as shown in FIG. 5, a wiring layer for each piezoresistive element P is formed on the entire upper surface. An insulating layer 513 in which 521 and 522 are embedded is formed, a common metal layer LE ^* is formed on the entire upper surface of the insulating layer 513, individual piezoelectric elements F are formed at predetermined positions on the upper surface, An individual upper electrode UE may be formed on the upper surface.

  Thus, in some regions, as shown in FIG. 25, the piezoresistive element and the piezoelectric element are formed so as to be in a laminated state with the insulating layer interposed therebetween, but in another part of the region, As shown in FIG. 26, only the piezoelectric element is formed on the insulating layer.

The material of the common metal layer LE ^* functioning as the lower electrode and the individual upper electrode UE may be any material as long as it can form a conductive layer that can function as an electrode. . In general, a metal such as aluminum may be used. However, in the embodiment shown here, as the common metal layer LE ^* , a two-layer film having a lower layer made of titanium and an upper layer made of platinum is used. This is because the insulating layer 513 located below the common metal layer LE ^* is composed of a silicon oxide film or a silicon nitride film, and the piezoelectric element F located above the common metal layer LE ^* is composed of PZT. This is a consideration to improve the suitability of. That is, if the lower layer of the common metal layer LE ^* is made of titanium, the bonding property to the insulating layer 513 made of a silicon oxide film or a silicon nitride film is excellent, and if the upper layer of the common metal layer LE ^* is made of platinum, PZT is used. The merit that it is excellent in the bondability to the piezoelectric element F is obtained. For the same reason, a two-layer film in which the lower layer is made of platinum and the upper layer is made of aluminum is used as the upper electrode UE.

In the example shown in FIG. 25, since the wiring layers 521 and 522 for the piezoresistive element P are embedded in the insulating layer 513, a common metal layer is used for connection to the wiring terminals T1 and T2. A contact hole may be opened at a predetermined portion of LE ^* and the insulating layer 523. In addition, among the wirings for the piezoelectric element F, the wiring for the lower electrode LE is sufficient if the common metal layer LE ^* and the wiring terminal L ^* are connected at any point. However, among the wiring to the piezoelectric element F, the wiring to the upper electrode UE needs to be performed separately for each of the eight sets of piezoelectric elements (that is, the upper electrode wiring terminal U shown in FIG. (Each piezoelectric element is independent and independent.) The wiring between the eight sets of upper electrodes UE and the wiring terminal U of the piezoelectric element, it is necessary to place over the common metal layer LE ^*, the common metal layer LE ^* is a conductive layer Therefore, it is necessary to form some kind of insulating layer thereon.

The use of a piezoelectric element layer as such an insulating layer provides the advantage of simplifying the manufacturing process. Originally, a piezoelectric element such as PZT itself has an insulating property, so that the piezoelectric element forming layer can be used as an insulating layer as it is. Moreover, as can be seen from the side sectional views of FIGS. 25 and 26, since the piezoelectric element F is a component formed on the upper surface of the common metal layer LE ^* , simultaneously with the process of forming the piezoelectric element F, If an insulating layer made of the same material as the piezoelectric element F is formed, a wiring layer for the upper electrode UE can be formed on the upper surface thereof.

Specifically, after forming the insulating layer 513 and the common metal layer LE ^* on the entire upper surface of the main body substrate 100, a piezoelectric element layer made of PZT is formed on the entire surface, and this piezoelectric element layer is patterned, and FIG. It suffices to leave only the area hatched with dots (the hatching in FIG. 27 indicates the remaining area of the piezoelectric element layer after patterning, not the cross section). The remaining area of the piezoelectric element layer shown in FIG. 27 is obtained by adding a wiring formation area A2 and a bonding pad formation area A3 to the piezoelectric element formation area A1 for forming the eight sets of piezoelectric elements shown in FIG. is there.

If a conductive layer of metal or the like is formed on the upper surface of the remaining region of the piezoelectric element layer shown in FIG. 27, a structure as shown in FIG. 28 is obtained. A hatched area in FIG. 28 is an area where a conductive layer is formed (the hatching in FIG. 28 indicates a conductive layer forming area, not a cross section). The conductive layer formed on the upper surface portion of the piezoelectric element formation region A1 shown in FIG. 27 becomes the upper electrode UE for the piezoelectric element, and the conductive layer formed on the upper surface portion of the wiring formation region A2 corresponds to the upper electrode UE. The conductive layer which is the wiring layer UW and is formed on the upper surface portion of the bonding pad formation region A3 becomes the bonding pad UB for the upper electrode UE (corresponding to the upper electrode wiring terminal U shown in FIGS. 25 and 26). . Incidentally, the bonding pad LB shown in FIG. 28 is a bonding pad formed directly on the upper surface of the common metal layer LE ^*, 25, which corresponds to the common metal layer LE ^* of the wiring terminals L ^* shown in FIG. 26 It is.

25 and 26, a common insulating layer 513 is formed on the upper surface of the main body substrate 100, and a wiring layer for each piezoresistive element P is embedded in the common insulating layer 513. A lower common conductive layer LE ^* is formed on the upper surface of the common insulating layer 513, and individual piezoelectric element layers F are formed on the upper surface of the lower common conductive layer LE ^*. The upper individual conductive layer UE is formed, and the upper individual conductive layers UE form the upper electrodes of the driving piezoelectric elements E1 to E4 and the detection piezoelectric elements D1 to D4, and the individual piezoelectric element layers. by F, the driving piezoelectric element E1~E4 and the detecting piezoelectric elements D1~D4 is constituted by individual parts of the lower common conductive layer LE ^*, the piezoelectric element E1~E4 and each for each drive Lower electrodes of the piezoelectric element D1~D4 for out will be configured.

In addition, when the structure shown in FIGS. 27 and 28 is adopted to perform wiring for each upper electrode UE, a wiring path (wiring forming region A2) for each upper electrode UE is provided on the upper surface of the lower common conductive layer LE ^*. ), And a wiring layer for each upper electrode UE is formed on the upper surface of the piezoelectric element patterning layer.

In another embodiment, the individual piezoelectric elements F can be replaced by a single common piezoelectric element F ^* in the same way that the individual lower electrodes LE can be replaced by a single common metal layer LE ^* . it can. FIG. 29 and FIG. 30 are enlarged side sectional views showing an example in which a plurality of piezoelectric elements F are physically configured by a single common piezoelectric element F ^* . FIG. 29 is a diagram regarding a region where both the piezoresistive element P and the piezoelectric element F need to be disposed, and FIG. 30 is a diagram regarding a region where only the piezoelectric element F needs to be disposed. In the examples shown in FIGS. 25 and 26, the individual piezoelectric elements F are formed in the individual regions, whereas in the examples shown in FIGS. 29 and 30, a single common piezoelectric element F ^* is formed on the main body substrate. 100 is formed on the entire upper surface of 100 (the upper surface of lower common conductive layer LE ^* ). Thus, even if the single common piezoelectric element F ^* is formed, if the upper electrodes UE are individually formed, individual portions of the single common piezoelectric element F ^* (individual upper electrode UE's) Since the immediately lower portion behaves as an independent piezoelectric element F, there is no problem in the operation of the sensor.

In FIG. 31, an insulating layer 513 (a wiring layer for each piezoresistive element P is embedded on the entire upper surface of the main body substrate 100 (with 12 sets of piezoresistive elements P formed on the surface layer portion) shown in FIG. And a lower common conductive layer LE ^* is formed, and a single common piezoelectric element F ^{* made} of PZT or the like is formed on the entire upper surface of the lower common conductive layer LE ^* . The portion hatched with dots in the figure is the formation region of the piezoelectric element layer (the hatching with dots in FIG. 31 does not indicate a cross section). As shown in the drawing, a wiring opening WW is provided in a part of the common piezoelectric element F ^* . Inside the wiring opening WW, the upper surface of the lower common conductive layer LE ^* located in the lower layer is exposed and functions as a contact hole. Common piezoelectric element F ^* is prepared in advance a plate member made of PZT, which to a may be formed in the step of attaching the upper surface of the lower common conductive layer LE ^*, the lower common conductive layer LE * ^(above As described above, PZT may be deposited by sputtering on the upper surface of a two-layer structure in which the lower layer is made of titanium and the upper layer is made of platinum to form a microcrystallized PZT thin film.

32, the upper electrode UE, the upper electrode wiring layer UW, and the upper electrode bonding pad UB are formed on the upper surface of the common piezoelectric element F ^* shown in FIG. 31, and the upper electrode bonding pad UB is further formed in the wiring opening WW. It is a top view which shows the state in which the bonding pad LB was formed. In practice, a conductive layer may be formed on the entire upper surface of the common piezoelectric element F ^* , and the conductive layer may be patterned to leave only necessary portions. The hatched portion in FIG. 32 shows the remaining region of the conductive layer after this patterning, and the dot-hatched portion has the conductive layer removed and the upper surface of the common piezoelectric element F ^* is exposed. A region is shown (hatching by hatching and dots in FIG. 32 does not indicate a cross section).

As described above, since a piezoelectric element such as PZT itself has an insulating property, the layer of the single common piezoelectric element F ^* shown in FIG. 31 itself functions as an insulating layer. Fulfill. Therefore, as shown in FIG. 32, even if the upper electrode UE, the upper electrode wiring layer UW, and the upper electrode bonding pad UB are directly formed on the upper surface thereof, they are not short-circuited with each other. Moreover, since the part in which the upper electrode UE is formed functions as an individual piezoelectric element, a sensor having substantially the same function as the basic embodiment shown in FIG. 1 can be obtained.

After all, in the sensor having the structure shown in FIGS. 29 and 30, a common insulating layer 513 is formed on the upper surface of the main body substrate 100, and a wiring layer for each piezoresistive element P is embedded in the common insulating layer 513. , on the upper surface of the common insulating layer 513 is formed lower common conductive layer LE ^*, on the upper surface of the lower common conductive layer LE ^* is common piezoelectric element layer F ^* is formed on the upper surface of the common piezoelectric element layer F ^* The upper individual conductive layers UE are formed, and the upper individual conductive layers UE form the upper electrodes of the drive piezoelectric elements E1 to E4 and the detection piezoelectric elements D1 to D4, respectively. the individual parts of F ^*, the driving piezoelectric element E1~E4 and the detecting piezoelectric elements D1~D4 is constituted by individual parts of the lower common conductive layer LE ^*, the piezoelectric element E1~ for each drive 4 and the lower electrode of each detecting piezoelectric element D1~D4 is to be configured. In addition, when the structure shown in FIGS. 31 and 32 is adopted, the wiring layer UW for each upper electrode UE is directly formed on the upper surface of the common piezoelectric element layer F ^* functioning as an insulating layer.

<<< §8. One-dimensional and two-dimensional acceleration / angular velocity detection >>>
The sensors according to the embodiments described so far are capable of independently detecting accelerations in the three axis directions of the acceleration αx in the X-axis direction, the acceleration αy in the Y-axis direction, and the acceleration αz in the Z-axis direction. A function as a sensor and a function as a three-dimensional angular velocity sensor capable of independently detecting angular velocities about three axes, an angular velocity ωx around the X axis, an angular velocity ωy around the Y axis, and an angular velocity ωz around the Z axis. Is a device having a function to be called a 6-axis motion sensor.

  However, in practice, it is not always necessary to detect all three-dimensional acceleration and three-dimensional angular velocity, so it is possible to detect the required axial acceleration and the necessary angular velocity around the axis according to the application. A simple sensor may be used.

  For example, for acceleration detection, only the components for the required detection axis are selected from the 12 sets of piezoresistive elements shown in FIG. 5 and the 3 sets of bridge circuits shown in FIG. Thus, it may be included as a component of the sensor.

  On the other hand, regarding the angular velocity detection, if a function for detecting angular velocities around two axes or one axis is sufficient, the motion of the weight body can be further simplified. That is, in §6, in order to detect the three-dimensional angular velocity, an example in which the weight body is circularly moved in a predetermined plane has been described. However, if it is sufficient to detect a two-dimensional angular velocity or a one-dimensional angular velocity, There is no need to circularly move the weight body, and it is sufficient to simply vibrate in one axial direction.

  FIG. 33 is a top view of a sensor having a detection function around two axes with respect to the angular velocity detection function (the acceleration detection function may be either one, two, or three axes). A region shown by hatching in the figure indicates a piezoelectric element formed on the upper surface of the main body substrate 100 (hatching does not indicate a cross section). The four sets of detection piezoelectric elements D11 to D14 shown in FIG. 33 are exactly the same as the detection piezoelectric elements D1 to D4 in the sensor according to the basic embodiment shown in FIG. However, the drive piezoelectric element E10 shown in FIG. 33 is a washer-like piezoelectric element, and has a form in which the four sets of drive piezoelectric elements E1 to E4 shown in FIG. 1 are connected to each other.

  The angular velocity detection by the sensor shown in FIG. 33 is performed as follows. First, when an AC signal such as a sine wave signal or a rectangular wave signal is given to the driving piezoelectric element E10, the main body substrate 100 alternately takes the deformed state shown in FIG. 8 and the deformed state shown in FIG. The weight body 210 simply vibrates in the Z-axis direction. Therefore, a detection circuit as shown in FIG. 24 is prepared, and signals output to the output terminals Tx and Ty are detected at a predetermined timing (for example, when passing through the center point of the amplitude of simple vibration). Then, since the signal output to the terminal Tx is a force component (Coriolis force) acting on the weight body 210 in the X-axis direction, the signal has a value corresponding to the angular velocity ωy around the Y-axis and is output to the terminal Ty. Since this signal is a force component (Coriolis force) in the Y-axis direction that has acted on the weight body 210, it has a value corresponding to the angular velocity ωx around the X-axis.

  Thus, both the angular velocity ωx around the X axis and the angular velocity ωy around the Y axis can be detected. Of course, even when a single AC signal is given to the four sets of driving piezoelectric elements E1 to E4 using the sensor shown in FIG. 1, the weight body 210 can be made to vibrate in the Z-axis direction. Similar to the sensor shown in FIG. 33, the sensor can be operated as a two-dimensional angular velocity sensor.

  In the illustrated example, the detection piezoelectric elements D11 to D14 are disposed in the region near the inner side of the annular intermediate portion 120, and the driving piezoelectric element E10 is disposed in the region near the outer side of the annular intermediate portion 120. The arrangement may be reversed. In short, one of the inner vicinity region and the outer vicinity region is set as a driving piezoelectric element arrangement region, and the other is set as a detection piezoelectric element arrangement region, and the driving piezoelectric element arrangement region surrounds the Z axis. An annular driving piezoelectric element E10 is arranged, the first detecting piezoelectric element D11 is arranged on the positive X axis in the detecting piezoelectric element arrangement region, and the second detecting piezoelectric element D12 is arranged on the negative X axis. Is arranged, the third detection piezoelectric element D13 is arranged on the positive Y axis, and the fourth detection piezoelectric element D14 is arranged on the negative Y axis. By supplying a single AC signal to the piezoelectric element E10, the signal generated in the first detection piezoelectric element D11 and the second detection piezoelectric element while vibrating the weight body 210 in the Z-axis direction. Y based on the difference from the signal generated at D12 If the angular velocity ωy around is detected, and the angular velocity ωx around the X axis is detected based on the difference between the signal generated in the third detecting piezoelectric element D13 and the signal generated in the fourth detecting piezoelectric element D14. Good.

  On the other hand, FIG. 34 is a top view of a sensor having only a detection function around one axis with respect to the detection function of angular velocity (the acceleration detection function may be either one axis, two axes, or three axes). A region shown by hatching in the figure indicates a piezoelectric element formed on the upper surface of the main body substrate 100 (hatching does not indicate a cross section). The four sets of detection piezoelectric elements D21, D22, E21, and E22 shown in FIG. 34 are exactly the same as the detection piezoelectric elements D1 to D4 in the sensor according to the basic embodiment shown in FIG. However, while the piezoelectric elements D21 and D22 are detection piezoelectric elements, the piezoelectric elements E21 and E22 are driving piezoelectric elements.

  The angular velocity detection by the sensor shown in FIG. 34 is performed as follows. First, a drive signal S1 shown in FIG. 19 is given to the drive piezoelectric element E21, and a drive signal S2 shown in FIG. 19 is given to the drive piezoelectric element E22 (the drive signal may be a rectangular wave). Then, the main body substrate 100 takes the deformation state shown in FIG. 6 and the deformation state shown in FIG. 7 alternately, and the weight body 210 vibrates in the X-axis direction. Therefore, a detection circuit as shown in the lower part of FIG. 24 is prepared (the upper electrode D3U is connected to the upper electrode of the piezoelectric element D21, and the upper electrode D4U is connected to the upper electrode of the piezoelectric element D22). Is connected), a signal output to the output terminal Ty is detected at a predetermined timing (for example, when passing through the center point of the amplitude of simple vibration). Then, since the signal output to the terminal Ty is a force component (Coriolis force) in the Y-axis direction that acts on the weight body 210, it becomes a value corresponding to the angular velocity ωz around the Z-axis, and the angular velocity around the Z-axis. It becomes possible to detect ωz.

  In short, the first driving piezoelectric element E21 is disposed on the positive X axis, the second driving piezoelectric element E22 is disposed on the negative X axis, and the first detecting piezoelectric element is disposed on the positive Y axis. The element D21 is arranged so that the second detection piezoelectric element D22 is arranged on the negative Y axis, and the angular velocity detection circuit is connected to the first drive piezoelectric element E21 and the second drive piezoelectric element E22. On the other hand, by supplying AC signals having opposite phases to each other, the signal generated in the first detection piezoelectric element D21 and the second detection piezoelectric element D22 are generated while vibrating the weight body 210 in the X-axis direction. The angular velocity ωz around the Z axis may be detected based on the difference from the signal.

<<< §9. Example of using an SOI substrate for the main substrate >>>
In the basic embodiment described so far, an N-type silicon substrate is used as the main body substrate 100. Here, an example in which an SOI (Silicon On Insulator) substrate is used instead of the N-type silicon substrate will be described. Note that a sensor using a silicon substrate or an SOI substrate can be mass-produced using the MEMS technology, and is optimal for miniaturization.

  FIG. 35 is a side cross-sectional view showing an example of a generally available SOI substrate. The illustrated SOI substrate 600 is an SOI substrate having a three-layer structure of an upper layer 610 made of N-type silicon, an intermediate layer 620 made of an insulating film of silicon oxide or silicon nitride, and a lower layer 630 made of N-type or P-type silicon serving as a base. It is. FIG. 36 is a side cross-sectional view showing a state where an annular groove 635 is formed by etching the lower layer 630 of the SOI substrate shown in FIG. 35 from the lower surface side. An inner portion 631 is formed inside the annular groove 635, and an outer portion 632 is formed outside. Thereafter, a P-type impurity is implanted into a predetermined portion of the upper surface layer portion of the upper layer 610 to form an embedded piezoresistive element P, and further, a piezoelectric element is formed on the upper surface thereof, thereby the main body used in the present invention. A substrate 100 can be formed.

  Thus, the first merit of configuring the main body substrate 100 using the SOI substrate is that the upper layer 610 and the lower layer 630 are separated by the middle layer 620 made of an insulating layer, so that the electrical behavior of each element is stabilized. It is a point that can be made to. When the piezoresistive element P is constituted by a P-type impurity-containing layer formed in an N-type silicon layer, a potential barrier due to a PN junction is formed at the boundary surface. It becomes possible. However, in practice, leakage current through the PN junction is unavoidable, and if this leakage current flows through the pedestal 220 to the apparatus housing side, correct detection cannot be performed. When the SOI substrate is used, as shown in FIG. 36, the upper layer 610 on which the piezoresistive element P is formed and the lower layer 632 joined to the pedestal 220 are electrically separated by the middle layer 620 made of an insulating layer. Therefore, adverse effects due to the above-described leakage current can be prevented.

  A second advantage of using the SOI substrate is that the thickness of the annular intermediate portion 120 that functions as a diaphragm can be easily controlled. Silicon constituting the lower layer 630 and silicon oxide (or silicon nitride) constituting the middle layer 620 have different etching characteristics. Therefore, when the annular groove 635 is dug by etching from the lower surface side of the SOI substrate, the middle layer 620 functions as an etch stopper, and the depth of the annular groove 635 can be accurately controlled to the thickness of the lower layer 630. Therefore, the thickness of the annular intermediate portion 120 exactly matches the sum of the thickness of the upper layer 610 and the thickness of the middle layer 620 for any portion.

  In the case of the structure shown in FIG. 36, since the annular intermediate portion 120 functioning as a diaphragm is a two-layer structure of the upper layer 610 and the middle layer 620, the temperature characteristics may be deteriorated due to the difference in thermal expansion coefficient between them. There is sex. For example, when a change occurs in the temperature of the environment in which the sensor is used, a stress may be generated in the annular intermediate portion 120 having a two-layer structure based on the change in temperature, thereby affecting the measurement value. In order to prevent such influence, the middle layer 620 is etched from the annular groove 635 shown in FIG. 36, and the middle layer 620 in the annular groove 635 is removed as shown in FIG. A portion 642 and an annular groove 645 may be formed. Then, the annular intermediate portion 120 that functions as a diaphragm is configured only from the upper layer 610. Of course, when etching the middle layer 620, the upper layer 610 having different etching characteristics functions as an etch stopper, so that the thickness of the annular intermediate portion 120 exactly matches the thickness of the upper layer 610 in any portion.

  However, considering that the insulating layer 513 is laminated on the upper surface of the upper layer 610, better temperature characteristics can be obtained if the annular intermediate portion 120 is left as a two-layer structure as shown in FIG. Sometimes. Therefore, in practice, it may be determined on a case-by-case basis whether to adopt the structure shown in FIG. 36 or the structure shown in FIG.

<<< §10. Device to prevent interference between acceleration detection and angular velocity detection >>>
The sensor according to the present invention has a function of detecting both acceleration and angular velocity. However, if both are detected simultaneously, there is a possibility that mutual interference occurs and a correct detection value cannot be obtained. For example, acceleration is detected by detecting the displacement of the weight body based on the acceleration. If the weight body is driven for angular velocity detection, the displacement due to this drive is erroneously detected as acceleration. There is a possibility that. The angular velocity is detected by detecting the displacement of the weight body based on the Coriolis force, but the displacement based on the acceleration may be erroneously detected as the angular velocity.

  As described above, in order to prevent mutual interference between the acceleration detection and the angular velocity detection, the weight body is driven at a frequency sufficiently higher than the acceleration detection target frequency band (for example, simple vibration or circular motion), and the acceleration detection circuit. And the angular velocity detection circuit may be provided with a filter circuit for cutting unnecessary signal components.

  In general applications, it is sufficient that the acceleration detection target frequency band is about several tens of Hz. Therefore, if the driving frequency of the weight body (the driving signals S1 and S2 shown in FIG. 19, the driving signals SS1 to SS4 shown in FIG. 20, and the driving signals SSS1 and SSS2 shown in FIG. 23) is set to several tens of kHz, The frequency band necessary for acceleration detection and the frequency band necessary for angular velocity detection can be separated by a filter circuit. For example, the driving frequency of the weight body is set to 20 kHz, and the acceleration detection circuit is provided with a filter circuit that cuts high frequency components of 100 Hz or more so as to exclude signal noise components caused by vibration of the weight body. The angular velocity detection circuit may be provided with a filter circuit that cuts low frequency components of 100 Hz or less so as to exclude signal noise components caused by acceleration.

  FIG. 38 is a circuit diagram showing a detection circuit employing such a filter circuit, and corresponds to an acceleration and angular velocity detection circuit used in the sensor shown in FIG. The upper part of the figure is the acceleration detection circuit 710, and the lower part of the figure is the angular velocity detection circuit 720. The terminals T11 to T13 of the acceleration detection circuit 710 are terminals to which voltages indicating initial detection values of the acceleration αx in the X-axis direction, the acceleration αy in the Y-axis direction, and the acceleration αz in the Z-axis direction are respectively applied. That is, the output voltages from the potentiometers 51, 52, and 53 shown in FIG. 18 are given to the terminals T11, T12, and T13. These output voltages are amplified by the amplifier circuits 71, 72, 73, passed through the filter circuits 81, 82, 83, and given to the terminals Tαx, Tαy, Tαz. The signals output from these terminals Tαx, Tαy, and Tαz indicate the detected values of the acceleration αx in the X-axis direction, the acceleration αy in the Y-axis direction, and the acceleration αz in the Z-axis direction, respectively.

  Here, the filter circuits 81, 82, 83 are, for example, low-pass filter circuits that cut high-frequency components of 100 Hz or higher, and high-frequency components included in signals indicating changes in the electrical resistance of the piezoresistive elements are cut. . Therefore, even if the output voltage from the potentiometers 51, 52, 53 shown in FIG. 18 includes a noise signal in the driving frequency band of the weight body, the detection signal output from the terminals Tαx, Tαy, Tαz. Does not contain such noise signals.

  On the other hand, the angular velocity detection circuit 720 includes amplifier circuits 74 and 75 that amplify voltages applied to the terminals T14 and T15, filter circuits 84 and 85, a synchronous detection circuit 91, a drive control circuit 92, and a final-stage amplifier. Circuits 76, 77, 78 are provided. In the circuit shown here, while the weight body 210 of the sensor shown in FIG. It has a function to detect. The drive control circuit 92 has a function of supplying the AC drive signals SS1 to SS4 as shown in FIG. 20 to the drive piezoelectric elements E1 to E4 to cause the weight body 210 to move circularly. A detection signal synchronized with the drive signals SS1 to SS4 is given from the drive control circuit 92 to the synchronous detection circuit 91. The synchronous detection circuit 91 can recognize the detection timing based on this detection signal. Conversely, a feedback signal is given from the synchronous detection signal 91 to the drive control circuit 92, and the drive control circuit 92 can perform drive correction based on this feedback signal as necessary.

  The voltage value of the terminal Tx of the circuit shown in FIG. 22 (value indicating the force in the X-axis direction acting on the weight body 210) is given to the terminal T14, and the terminal Tz of the circuit shown in FIG. Voltage value (value indicating the force in the Z-axis direction acting on the weight body 210) is given. The detection target signals given to the terminals T14 and T15 are amplified by the amplifier circuits 74 and 75, and then given to the synchronous detection circuit 91 through the filter circuits 84 and 85. Here, the filter circuits 84 and 85 are high-pass filter circuits that cut low-frequency components included in AC signals generated in the detection piezoelectric elements D1 to D4. For example, if a high-pass filter circuit that cuts a low frequency component of 100 Hz or less is used, a signal component caused by acceleration in a general application can be removed.

  The synchronous detection circuit 91 is a circuit that performs synchronous detection based on the detection signal supplied from the drive control circuit 92 with respect to the AC signal that has passed through the high-pass filter circuits 84 and 85. Specifically, based on the detection signal, the moment when the weight body 210 passes through the XZ plane (the moment when the weight body moves with the velocity component in the Y-axis direction) is detected, and the detection target signal at that time point is detected. Based on (a signal indicating the X-axis direction force acting on the weight body from the terminal T14 and a signal indicating the Z-axis direction force acting on the weight body from the terminal T15), the angular velocity ωz around the Z axis And the angular velocity ωx about the X axis can be obtained. Further, the moment when the weight body 210 passes through the YZ plane (the moment when the weight body moves with the velocity component in the X-axis direction) is detected, and the detection target signal at that time (the weight body from the terminal T15 is applied to the weight body). The angular velocity ωy about the Y axis can be obtained based on the signal indicating the applied Z-axis direction force.

  Thus, the signals indicating the angular velocities ωx, ωy, and ωz obtained by the synchronous detection circuit 91 are amplified by the amplifier circuits 76, 77, and 78, and then output from the terminals Tωx, Tωy, and Tωz.

  The synchronous detection circuit 91 monitors whether or not the weight body is moving with a correct amplitude (radius in the case of circular movement) based on the detection target signal, and the result is used as a feedback signal to drive control circuit 92. To give. The drive control circuit 92 appropriately controls the amplitudes of the drive signals SS1 to SS4 based on the feedback signal.

<<<< §11. Features of the sensor according to the present invention >>>
Finally, individual characteristics of the sensor according to the present invention will be described. The most important feature of the sensor according to the present invention is that acceleration is detected by a piezoresistive element and angular velocity is detected by a piezoelectric element. Here, the change in the electrical resistance of the piezoresistive element is a static physical phenomenon. For example, as shown in FIG. 6, a constant force + Fx continues to act, and the annular intermediate portion 120 always has a constant deformation state. Even if maintained, the electrical resistance of the piezoresistive element formed in the annular intermediate portion 120 is maintained at a constant value depending on the deformation state. Therefore, it can be detected even in a state where steady acceleration is acting like gravitational acceleration.

  As described above, the piezoresistive element has an advantage that static state detection is possible, but cannot be used as a drive element. In order to detect the angular velocity, as described above, it is necessary to move the weight body in a predetermined direction, and a driving element is required. Therefore, a piezoelectric element is employed as the driving element. The piezoelectric element can function as a detection element that generates a voltage in response to deformation of the annular intermediate portion 120, and can also function as a drive element that generates displacement by supplying a drive signal.

  However, a piezoelectric element cannot detect a static deformation state unlike a piezoresistive element, and its function as a detection element is limited to detection of a dynamic transient phenomenon. For example, when the weight body 210 is moved in the positive direction of the X axis as shown in FIG. 6 by the action of force + Fx, the piezoelectric element fixed to the upper surface of the annular intermediate portion 120 is subjected to its transient deformation. Charges are temporarily generated. However, when the weight body 210 is stationary at the position shown in FIG. 6 and the annular intermediate portion 120 is maintained in the deformed state shown in the figure, no charge is generated in the piezoelectric element.

  As described above, the detection function of the piezoelectric element is limited to detection of a dynamic deformation state, but such a limited detection function is sufficient when the angular velocity is detected. As described above, the weight body 210 is driven to perform a simple vibration or a circular motion. These motions are motions in which the magnitude or direction of the velocity V of the weight body 210 changes with time. Therefore, the magnitude and direction of the Coriolis force Fc acting on the weight body 210 also change with time, and eventually the Coriolis force Fc to be detected is not detected as a static amount, It will be detected as a transient phenomenon. Therefore, there is no problem even if a piezoelectric element is used as the detection element.

  In the present invention, the reason why acceleration is detected by a piezoresistive element and angular velocity is detected by a piezoelectric element is due to such circumstances. In addition, since the piezoresistive element and the piezoelectric element can be formed on the upper surface of the annular intermediate portion 120, there is an advantage that the wiring is simplified. For example, when a capacitive element is used as a detection element or a drive element, one of a pair of electrodes constituting the capacitive element needs to be provided on the weight body side, and wiring for each electrode must be complicated. Absent. In addition, when a capacitive element is used, detection based on a minute change in the distance between the electrodes is necessary. Therefore, in practice, it is necessary to maintain the inside in a vacuum so that the movement of the weight body is not hindered by air. . When a piezoresistive element or a piezoelectric element is used as the detection element, it is not necessary to maintain the inside in a vacuum, and the structure can be simplified.

  Further, the sensor according to the present invention has a structure in which a weight body 210 is joined to the lower surface of the inner portion 110 of the main body substrate 100 as shown in FIG. The important point here is that the planar shape of the weight body 210 is larger than the planar shape of the inner portion 110 when viewed from above. In other words, the contour line of the projection image when the weight body 210 is vertically projected onto the upper surface of the main body substrate 100 has a structure located outside the inner portion 110 of the main body substrate 100, so to speak, A large block-like weight body 210 is joined to the lower surface of the portion 110.

  The first merit of such a structure is that the mass of the weight body 210 can be sufficiently secured. If the weight body 210 is constituted by a large lump and a large mass is secured, sufficient deformation of the annular intermediate portion 120 can be caused by the action of minute acceleration or the action of minute Coriolis force. Thus, the sensitivity of the sensor can be improved.

  The second merit is that it becomes easy to design a structure having a practically optimal resonance frequency. In order to detect the angular velocity, it is necessary to cause the weight body 210 to perform a periodic motion such as a simple vibration or a circular motion. However, the driving frequency is preferably set to 15 kHz or more in practice. This is because when the driving frequency is lower than that, the driving sound of the weight body 210 is heard as noise because it overlaps the human audible frequency range. On the other hand, since acceleration and angular velocity sensors are built in various devices, they must always meet demands for miniaturization. For example, to make a sensor that meets the demands of the industry, the planar size is about 3 to 5 mm square, the thickness is about 0.3 to 1 mm, and the thickness of the annular intermediate portion 120 that functions as a diaphragm is about 5 to 10 μm. It is necessary to design to. In designing a mechanical structure that meets such dimensional conditions and has a resonance frequency of 15 kHz or more, a structure in which a large block of weight 210 is joined to the lower surface of the inner portion 110 is extremely advantageous.

  In addition, in order to improve the detection sensitivity of the angular velocity sensor, the condition that the resonance frequency related to the moving direction of the weight body and the resonance frequency related to the direction of Coriolis force generation (generally called “bi-resonance”). It is necessary to use a structure satisfying the above. Usually, the design is such that the difference between the resonance frequencies in the two directions is about 1%. The technique of joining a large block-like weight body 210 to the lower surface of the inner portion 110 is advantageous in designing a structure that satisfies such a dual resonance condition.

  In particular, in the sensor structure shown as the basic embodiment, the inner contour line C1 and the outer contour line C2 of the projected image when the annular groove 140 is vertically projected onto the upper surface of the main body substrate 100 are concentric (see FIG. 5). ), The weight body 120 is a columnar shape having a central axis of “an axis orthogonal to the upper surface of the main body substrate 100 and passing through the centers of the concentric circles C1 and C2” (in the embodiment, the columnar shape is a prismatic column, A weight body may be used). Such a structure is very preferable in satisfying the condition of dual resonance.

  In the sensor shown as the basic embodiment, the piezoresistive element P, the driving piezoelectric elements E1 to E4, and the detecting piezoelectric elements D1 to D4 are in contact with the inner contour line C1 or the outer contour line C2 of the annular groove forming region. Placed in position. This is extremely effective for increasing detection sensitivity and driving efficiency. In the deformation of the annular intermediate portion 120 as shown in FIGS. 6 to 9, the portion where the stress is most concentrated is the portion of the inner contour line C1 or the outer contour line C2 (that is, the base portion of the diaphragm). Therefore, it is very reasonable to place each element in this part.

  Furthermore, in the sensor according to the present invention, the fan-shaped piezoelectric element is formed on the washer-shaped annular intermediate portion 120 along the inner contour line C1 or the outer contour line C2. A relatively large area can be secured. This is effective for increasing the detection sensitivity and driving efficiency of the piezoelectric element. The charge generated in the piezoelectric element increases as the area of the electrodes formed above and below it increases, so that the detection area and drive efficiency improve as the planar area of the piezoelectric element increases.

1 is a top view of a sensor according to a basic embodiment of the present invention. It is the sectional side view which cut | disconnected the sensor shown in FIG. 1 by XZ plane. FIG. 3 is a plan sectional view of the sensor shown in FIG. 2 cut along a cutting line 3-3. FIG. 4 is a plan sectional view of the sensor shown in FIG. 2 cut along a cutting line 4-4. It is a top view which shows the state which removed each piezoelectric element D1-D4, E1-E4 from the sensor shown in FIG. It is a sectional side view which shows a deformation | transformation state when the force + Fx of the X-axis positive direction acts on the weight body 210 of the sensor shown in FIG. It is a sectional side view which shows a deformation | transformation state when force -Fx of the X-axis negative direction acts on the weight body 210 of the sensor shown in FIG. It is a sectional side view which shows a deformation | transformation state when force + Fz of the Z-axis positive direction acts on the weight body 210 of the sensor shown in FIG. FIG. 3 is a side sectional view showing a deformed state when a force −Fz in the negative Z-axis direction acts on the weight body 210 of the sensor shown in FIG. 2. FIG. 3 is a top view showing a stretched state at each position on the top surface of the annular intermediate portion 120 when a force + Fx in the X-axis positive direction is applied to the weight body 210 of the sensor shown in FIG. 1. FIG. 3 is a top view showing a stretched state at each position on the top surface of the annular intermediate portion 120 when a force −Fx in the negative X-axis direction acts on the weight body 210 of the sensor shown in FIG. 1. FIG. 3 is a top view showing an expanded / contracted state at each position on the upper surface of the annular intermediate portion 120 when a force + Fy in the positive direction of the Y-axis acts on the weight body 210 of the sensor shown in FIG. 1. FIG. 3 is a top view illustrating a stretched state at each position on the top surface of the annular intermediate portion 120 when a force −Fy in the negative Y-axis direction is applied to the weight body 210 of the sensor illustrated in FIG. 1. FIG. 3 is a top view showing a state of expansion and contraction at each position on the top surface of the annular intermediate portion 120 when a force + Fz in the positive direction of the Z axis is applied to the weight body 210 of the sensor shown in FIG. 1. FIG. 3 is a top view showing a stretched state at each position on the top surface of the annular intermediate portion 120 when a force −Fz in the negative Z-axis direction acts on the weight body 210 of the sensor shown in FIG. 1. It is an expanded sectional side view of the formation part of the piezoresistive element of the sensor shown in FIG. It is an expanded sectional side view of the formation part of the piezoelectric element of the sensor shown in FIG. It is a circuit diagram which shows an example of the acceleration detection circuit used for the sensor shown in FIG. It is a wave form diagram which shows the drive signal used in order to vibrate the weight body 210 of the sensor shown in FIG. It is a wave form diagram which shows the drive signal used in order to carry out circular motion of the weight body 210 of the sensor shown in FIG. 1 within a plane parallel to XY plane. It is a perspective view which shows the state which the weight body is carrying out the circular motion in XY plane. FIG. 2 is a circuit diagram showing an example of a circuit that detects a Coriolis force Fx in the X-axis direction and a Coriolis force Fz in the Z-axis direction that act on the weight body 210 of the sensor shown in FIG. 1. It is a wave form diagram which shows the drive signal used in order to circularly move the weight body 210 of the sensor shown in FIG. 1 within an XZ plane. FIG. 2 is a circuit diagram showing an example of a circuit that detects a Coriolis force Fx in the X-axis direction and a Coriolis force Fy in the Y-axis direction that act on the weight body 210 of the sensor shown in FIG. 1. FIG. 2 is an enlarged side cross-sectional view of a superimposed formation portion of a piezoresistive element and a piezoelectric element on a main body substrate 100 of the sensor shown in FIG. 1. FIG. 2 is an enlarged side sectional view of a piezoelectric element forming portion on a main body substrate 100 of the sensor shown in FIG. 1. It is a top view which shows each piezoelectric element layer and piezoelectric element patterning layer of the sensor which has a structure shown in FIG. 25 and FIG. 26 as a hatching area | region (hatching does not show a cross section). It is a top view which shows the conductive layer formed in the upper surface of each piezoelectric element layer and piezoelectric element patterning layer shown in FIG. 27 as a hatching area | region (hatching does not show a cross section). It is an expanded sectional side view which shows the modification of the superimposition formation part of a piezoresistive element and a piezoelectric element on the main body board | substrate 100 of the sensor shown in FIG. It is an expanded sectional side view which shows the modification of the piezoelectric element formation part on the main body board | substrate 100 of the sensor shown in FIG. It is a top view which shows the piezoelectric element layer of the sensor which has a structure shown in FIG. 29 and FIG. 30 as a hatching area | region (hatching does not show a cross section). FIG. 32 is a top view showing a conductive layer formed on the top surface of the piezoelectric element layer shown in FIG. 31 as a hatched region (hatching does not indicate a cross section). It is a top view of the sensor which concerns on the modification which detects the angular velocity about 2 axes | shafts (hatching does not show a cross section). It is a top view of the sensor which concerns on the modification which detects the angular velocity about 1 axis | shaft (hatching does not show a cross section). FIG. 3 is a side sectional view showing a first stage of a manufacturing process in which the main body substrate 100 of the sensor shown in FIG. 1 is configured using an SOI substrate. FIG. 4 is a side sectional view showing a second stage of a manufacturing process in which the main body substrate 100 of the sensor shown in FIG. 1 is configured using an SOI substrate. FIG. 4 is a side sectional view showing a third stage of a manufacturing process in which the main body substrate 100 of the sensor shown in FIG. 1 is configured using an SOI substrate. It is a circuit diagram which shows an example of the detection circuit of the acceleration and angular velocity used for the sensor shown in FIG.

Explanation of symbols

50: DC power supplies 51-53: potentiometers 61-64: calculators 71-78: amplifier circuits 81-85: filter circuit 91: synchronous detection circuit 92: drive control circuit 100: main body substrate 110: inner part 120: annular intermediate Part 130: outer part 140: annular groove 200: auxiliary substrate 210: weight body 220: pedestal 300: support substrate 511, 512, 513: insulating layer 521, 522: wiring layer 600: SOI substrate 610: silicon layer 620: oxidation Silicon layer / silicon nitride layer 630: silicon layer 631: inner part 632: outer part 635: annular groove 641: inner part 642: outer part 645: annular groove 710: acceleration detection circuit 720: angular velocity detection circuit A1: piezoelectric element formation region A2: Wiring forming area A3: Bonding pad forming area C1: Inner outline C2 of the annular groove C2: Outer outline d1 of the annular groove 3: pore size D1~D4, D11~D14, D21, D22: detecting piezoelectric elements D1U～D4U: upper electrode E1~E4 the detecting piezoelectric elements, E10, E21, E22: driving piezoelectric element F: a piezoelectric element F ^* : Common piezoelectric element layer + Fx: Force acting in the X-axis positive direction + Fy: Force acting in the Y-axis positive direction + Fz: Force acting in the Z-axis positive direction-Fx: Force acting in the X-axis negative direction-Fy: Force acting in the negative direction of the Y axis -Fz: Force acting in the negative direction of the Z axis G: Gravity center of the weight H: Circular orbit L: Terminal for wiring L ^{* of the} lower electrode: Terminal LB for wiring of the common metal layer: Lower electrode bonding pad LE: Lower electrode LE ^* : Common metal layer constituting lower electrode O: Origin of coordinate system P: Piezoresistive elements Px1 to Px4: Piezoresistive elements Py1 to Py4 for detecting acceleration in the X-axis direction: For acceleration detection in the Y-axis direction Piezoresistive elements Pz1 to Pz4: Piezoresistive elements Q1 to Q4 for detecting acceleration in the Z-axis direction: passing points S1 and S2 on a circular orbit: drive signals SS1 to SS4: drive signals SSS1 and SSS2: drive signal t: time axis t1 to t4: period T1, T2, T11 to T15: wiring terminals Tx, Ty, Tz: output terminals Tαx, Tαy, Tαz: acceleration detection signal output terminals Tωx, Tωy, Tωz: angular velocity detection signal output terminals U : Upper electrode wiring terminal UB: Upper electrode bonding pad UE: Upper electrode UW: Upper electrode wiring layer Vx, Vy, Vz: Bridge voltage / moving speed WW: Wiring openings X, Y, Z: Three-dimensional Each coordinate axis Xa, Xb in the Cartesian coordinate system: auxiliary axis parallel to the X axis

Claims (17)

An annular groove is formed on the lower surface, and an inner part located inside the annular groove forming area, an outer part located outside the annular groove forming area, and an annular intermediate part located in the annular groove forming area, The annular intermediate portion is flexible so that the inner portion can be displaced with respect to the outer portion; and
A weight body connected to the lower surface of the inner portion;
A pedestal connected to the lower surface of the outer portion and fixed to the apparatus housing so as to surround the weight body;
A piezoresistive element embedded in the annular intermediate portion;
A driving piezoelectric element and a detecting piezoelectric element fixed to the surface of the annular intermediate portion;
An acceleration detection circuit for detecting an acceleration acting based on a change in electrical resistance of the piezoresistive element;
An angular velocity applied based on a signal generated in the detecting piezoelectric element while supplying an alternating current signal to the driving piezoelectric element to periodically deform the annular intermediate portion and causing a periodic motion in the weight body An angular velocity detection circuit for detecting
A sensor that detects both acceleration and angular velocity. The sensor according to claim 1, wherein
The acceleration detection circuit has a low-pass filter circuit that cuts a high-frequency component included in a signal indicating a change in the electrical resistance of the piezoresistive element, and the signal component that has passed through the low-pass filter circuit is used as an acceleration detection value. Output,
The angular velocity detection circuit supplies an AC signal to the drive piezoelectric element to control the periodic movement of the weight body, and a high frequency cut off low frequency component included in the AC signal generated in the detection piezoelectric element. A synchronous detection circuit that performs synchronous detection based on a detection signal supplied from the drive control circuit with respect to the AC signal that has passed through the high-pass filter circuit, and the synchronous detection circuit A sensor for detecting both acceleration and angular velocity, wherein the detection result is output as a detected value of angular velocity. The sensor according to claim 1 or 2,
A sensor for detecting both an acceleration and an angular velocity, wherein a contour line of a projection image when a weight body is vertically projected onto an upper surface of a main body substrate is positioned outside an inner portion of the main body substrate. The sensor according to any one of claims 1 to 3,
When the annular groove is vertically projected on the upper surface of the main body substrate, the inner contour line and the outer contour line of the projected image form concentric circles,
A sensor for detecting both acceleration and angular velocity, wherein the weight body has a columnar shape centering on an "axis orthogonal to the upper surface of the main body substrate and passing through the center of the concentric circle". The sensor according to any one of claims 1 to 4,
A sensor for detecting both acceleration and angular velocity, wherein the piezoresistive element, the driving piezoelectric element, and the detecting piezoelectric element are arranged at a position in contact with the inner contour line or the outer contour line of the annular groove forming region. . The sensor according to any one of claims 1 to 5,
The body substrate is composed of a single silicon substrate or SOI substrate, and the piezoresistive element is composed of a silicon impurity-containing layer formed on the surface layer portion of the body substrate. Sensor that detects both angular velocity. The sensor according to any one of claims 1 to 6,
An XYZ three-dimensional coordinate system is defined such that the origin O is located at the center of the inner side of the upper surface of the main body substrate and the XY plane is located on the upper surface of the main body substrate. When the neighborhood part of is defined as the inner neighborhood area and the neighborhood part of the outer contour line is defined as the outer neighborhood area,
A first X-axis detection piezoresistive element is disposed in the outer vicinity region on the positive X-axis, and a second X-axis detection piezoresistive element is disposed in the inner vicinity region on the positive X-axis. A third X-axis detection piezoresistive element is disposed in the inner vicinity region on the X-axis, and a fourth X-axis detection piezoresistive element is disposed in the outer vicinity region on the negative X-axis;
A first Y-axis detection piezoresistive element is disposed in the outer vicinity region on the positive Y-axis, and a second Y-axis detection piezoresistive element is disposed in the inner vicinity region on the positive Y-axis. A third Y-axis detecting piezoresistive element is disposed in the inner vicinity region on the Y-axis, and a fourth Y-axis detecting piezoresistive element is disposed in the outer vicinity region on the negative Y-axis,
A first Z-axis detection piezoresistive element is disposed at an arbitrary position in the outer vicinity area, and a second Z-axis detection piezoresistive element is disposed at an arbitrary position in the inner vicinity area. A third Z-axis detecting piezoresistive element is disposed at a position, and a fourth Z-axis detecting piezoresistive element is disposed at an arbitrary position in the outer vicinity region;
An acceleration detection circuit uses the first X-axis detection piezoresistive element and the third X-axis detection piezoresistive element as a first opposite side, the second X-axis detection piezoresistive element, and the fourth The acceleration acting in the X-axis direction is detected based on the bridge voltage of the bridge circuit having the X-axis detecting piezoresistive element as the second opposite side, and the first Y-axis detecting piezoresistive element and the third The bridge voltage of the bridge circuit having the Y-axis detecting piezoresistive element as the first opposite side and the second Y-axis detecting piezoresistive element and the fourth Y-axis detecting piezoresistive element as the second opposite side , The acceleration acting in the Y-axis direction is detected, the first Z-axis detecting piezoresistive element and the fourth Z-axis detecting piezoresistive element are set as the first opposite sides, and the second Z-axis is detected. Axis detection piezoresistive element and Both acceleration and angular velocity are detected by detecting acceleration acting in the Z-axis direction based on the bridge voltage of the bridge circuit having the third Z-axis detection piezoresistive element as the second opposite side. Sensor. The sensor according to any one of claims 1 to 7,
An XYZ three-dimensional coordinate system is defined such that the origin O is located at the center of the inner side of the upper surface of the main body substrate and the XY plane is located on the upper surface of the main body substrate. When the neighborhood part of is defined as the inner neighborhood area and the neighborhood part of the outer contour line is defined as the outer neighborhood area,
One of the inner vicinity area and the outer vicinity area is set as a driving piezoelectric element arrangement area, and the other is set as a detection piezoelectric element arrangement area,
A first driving piezoelectric element is arranged on the positive X axis in the driving piezoelectric element arrangement region, a second driving piezoelectric element is arranged on the negative X axis, and a third on the positive Y axis. And a fourth driving piezoelectric element is arranged on the negative Y-axis,
A first detection piezoelectric element is arranged on the positive X axis in the detection piezoelectric element arrangement region, a second detection piezoelectric element is arranged on the negative X axis, and a third on the positive Y axis. Are arranged, and a fourth detection piezoelectric element is arranged on the negative Y-axis,
The angular velocity detection circuit supplies an alternating current signal whose phase is shifted by π / 2 to each driving piezoelectric element, thereby causing the weight body to move circularly within a plane parallel to the XY plane. An angular velocity around the Z axis is detected based on a difference between a signal generated in the first detection piezoelectric element and a signal generated in the second detection piezoelectric element at the time of passing through the XZ plane, and the weight body is detected in the XZ plane. The angular velocity around the X axis is detected based on the sum of the signal generated in the third detection piezoelectric element and the signal generated in the fourth detection piezoelectric element at the time of passing through, and the weight body passes through the YZ plane. The angular velocity around the Y axis is detected based on the sum of the signal generated in the third detection piezoelectric element and the signal generated in the fourth detection piezoelectric element at the time of The sensor to detect. The sensor according to any one of claims 1 to 7,
An XYZ three-dimensional coordinate system is defined such that the origin O is located at the center of the inner side of the upper surface of the main body substrate and the XY plane is located on the upper surface of the main body substrate. When the neighborhood part of is defined as the inner neighborhood area and the neighborhood part of the outer contour line is defined as the outer neighborhood area,
One of the inner vicinity area and the outer vicinity area is set as a driving piezoelectric element arrangement area, and the other is set as a detection piezoelectric element arrangement area,
A first driving piezoelectric element is disposed on the positive X axis of the driving piezoelectric element arrangement region, and a second driving piezoelectric element is disposed on the negative X axis;
A first detection piezoelectric element is arranged on the positive X axis in the detection piezoelectric element arrangement region, a second detection piezoelectric element is arranged on the negative X axis, and a third on the positive Y axis. Are arranged, and a fourth detection piezoelectric element is arranged on the negative Y-axis,
The angular velocity detection circuit supplies an AC signal whose phase is shifted by π / 2 to the first driving piezoelectric element and the second driving piezoelectric element, so that the weight body is placed in the XZ plane. Based on the difference between the signal generated in the first detection piezoelectric element and the signal generated in the second detection piezoelectric element when the weight body is moving in the Z-axis direction. X is determined based on a difference between a signal generated in the third detecting piezoelectric element and a signal generated in the fourth detecting piezoelectric element at a time when the surrounding angular velocity is detected and the weight body moves in the Z-axis direction. Based on a difference between a signal generated in the third detecting piezoelectric element and a signal generated in the fourth detecting piezoelectric element when the angular velocity around the axis is detected and the weight body moves in the X-axis direction. Acceleration characterized by detecting angular velocity around the Z axis A sensor for detecting both the angular velocity. The sensor according to any one of claims 1 to 7,
An XYZ three-dimensional coordinate system is defined such that the origin O is located at the center of the inner side of the upper surface of the main body substrate and the XY plane is located on the upper surface of the main body substrate. When the neighborhood part of is defined as the inner neighborhood area and the neighborhood part of the outer contour line is defined as the outer neighborhood area,
One of the inner vicinity area and the outer vicinity area is set as a driving piezoelectric element arrangement area, and the other is set as a detection piezoelectric element arrangement area,
An annular driving piezoelectric element surrounding the Z axis is arranged in the driving piezoelectric element arrangement region,
A first detection piezoelectric element is arranged on the positive X axis in the detection piezoelectric element arrangement region, a second detection piezoelectric element is arranged on the negative X axis, and a third on the positive Y axis. Are arranged, and a fourth detection piezoelectric element is arranged on the negative Y-axis,
The angular velocity detection circuit supplies a single alternating current signal to the driving piezoelectric element, thereby causing a signal generated in the first detection piezoelectric element and the second while vibrating the weight body in the Z-axis direction. The angular velocity around the Y-axis is detected based on the difference between the signal generated in the detection piezoelectric element and the difference between the signal generated in the third detection piezoelectric element and the signal generated in the fourth detection piezoelectric element. A sensor for detecting both an acceleration and an angular velocity, characterized by detecting an angular velocity around an X axis. The sensor according to any one of claims 1 to 7,
When defining an XYZ three-dimensional coordinate system in which the origin O is located at the center of the inner side of the upper surface of the main body substrate and the XY plane is located on the upper surface of the main body substrate
A first drive piezoelectric element is disposed on the positive X axis, a second drive piezoelectric element is disposed on the negative X axis, and a first detection piezoelectric element is disposed on the positive Y axis. , A second detection piezoelectric element is disposed on the negative Y-axis,
While the angular velocity detection circuit supplies alternating current signals having opposite phases to the first driving piezoelectric element and the second driving piezoelectric element, the weight body is vibrated in the X-axis direction, A sensor for detecting both acceleration and angular velocity, characterized by detecting an angular velocity around the Z axis based on a difference between a signal generated in the first detecting piezoelectric element and a signal generated in the second detecting piezoelectric element. . The sensor according to any one of claims 1 to 11,
A lower electrode is formed on the lower surface of the driving piezoelectric element and the detecting piezoelectric element, and an upper electrode is formed on the upper surface. The lower electrode of each piezoelectric element is fixed to the upper surface of the annular intermediate portion via an insulating layer. Has been
The angular velocity detection circuit applies an AC voltage between the upper electrode and the lower electrode of the driving piezoelectric element to cause a periodic motion in the weight body, while the upper electrode and the lower electrode of the detection piezoelectric element A sensor for detecting both an acceleration and an angular velocity, characterized in that an angular velocity acting on the basis of an alternating voltage generated therebetween is detected. The sensor according to claim 12, wherein
A sensor for detecting both acceleration and angular velocity, wherein lower electrodes of a plurality of piezoelectric elements are physically constituted by a single common conductive layer. The sensor according to claim 12 or 13,
A sensor for detecting both acceleration and angular velocity, wherein a plurality of piezoelectric elements are physically constituted by a single common piezoelectric element layer. The sensor according to claim 12, wherein
A common insulating layer is formed on the upper surface of the main substrate, a lower common conductive layer is formed on the upper surface of the common insulating layer, and individual piezoelectric element layers are formed on the upper surface of the lower common conductive layer. Each upper individual conductive layer is formed on the upper surface,
Each upper individual conductive layer constitutes an upper electrode of each driving piezoelectric element and each detection piezoelectric element, and each individual piezoelectric element layer constitutes each driving piezoelectric element and each detection piezoelectric element, The lower electrode of each driving piezoelectric element and each detecting piezoelectric element is constituted by individual portions of the lower common conductive layer,
On the upper surface of the lower common conductive layer, there is formed a piezoelectric element patterning layer patterned along the wiring path for each upper electrode,
The wiring layer for each piezoresistive element is embedded in the common insulating layer,
A sensor for detecting both acceleration and angular velocity, wherein a wiring layer for each upper electrode is formed on an upper surface of the piezoelectric element patterning layer. The sensor according to claim 12, wherein
A common insulating layer is formed on the upper surface of the main substrate, a lower common conductive layer is formed on the upper surface of the common insulating layer, a common piezoelectric element layer is formed on the upper surface of the lower common conductive layer, and an upper surface of the common piezoelectric element layer. In each case, an upper individual conductive layer is formed,
The upper individual conductive layers constitute upper electrodes of the drive piezoelectric elements and the detection piezoelectric elements, and the drive piezoelectric elements and the detection piezoelectric elements constitute the individual portions of the common piezoelectric element layer. The lower common conductive layer is composed of the lower electrode of each driving piezoelectric element and each detecting piezoelectric element,
A wiring layer for each piezoresistive element is embedded in the insulating layer,
A sensor for detecting both acceleration and angular velocity, wherein a wiring layer for each upper electrode is formed on an upper surface of the common piezoelectric element layer. The sensor according to any one of claims 1 to 16,
A sensor for detecting both acceleration and angular velocity, wherein a piezoresistive element and a piezoelectric element are formed in a laminated state with at least an insulating layer interposed therebetween in a part of the region.

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