JPH11118826A - Micromachine sensor - Google Patents

Abstract

(57) [Problem] To prevent S / N deterioration due to capacitive coupling between a wiring on a substrate and a detection element. Prevents lowering of detection accuracy due to electrostatic attraction between the wiring and the thin film movable body. SOLUTION: A thin-film movable body (14, 15, 17, 18) arranged substantially in parallel with a gap with respect to a substrate (1, 2), an element (20) for detecting its displacement, and a wiring (3, The micromachine sensor according to (5) includes a conductive film (8) that covers the wirings (3, 5) at an insulating distance. GND connection between thin film movable body and conductive film. An element (20) for driving the thin-film movable body to vibrate, an element (4) for detecting the displacement of the thin-film movable body, and wiring (3, 3) on the substrate connected to these elements (20, 4) 5), and the wiring (3, 5)
An angular velocity sensor having a conductive film (8) positioned substantially over the entire length of the sensor.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a micromachine sensor having a thin-film movable body floatingly supported on a substrate and an element for detecting its displacement, for measuring physical quantities such as displacement, angular velocity, acceleration, and the like. Although not intended to be limited to this, a thin film semiconductor having comb teeth and support beams is formed on a substrate by micro-machining technology so as to be movable from the substrate in a direction parallel or perpendicular to the substrate surface. The present invention relates to a micromachine in which an electrode for detecting a displacement of a semiconductor is formed on a substrate.

[0002]

2. Description of the Related Art In this type of micromachine, a conductive thin film semiconductor is formed movably with respect to a substrate, a detection electrode facing the thin film semiconductor is formed on the substrate, and the displacement of the thin film semiconductor is detected by the detection electrode. There is a displacement sensor to detect using. This displacement sensor can be used as an acceleration sensor because the thin film semiconductor is displaced in the direction (displacement detection axis) in which the thin film semiconductor and the detection electrode face each other when acceleration is applied. When a fluid flowing in the direction (displacement detection axis) facing the thin-film semiconductor and the detection electrode contacts the thin-film semiconductor, the thin-film semiconductor is displaced in the direction corresponding to the flow velocity, so that it can be used as a flow rate sensor. When the displacement detection axis is perpendicular to the plane of the thin-film semiconductor and a fluid pressure is applied in the direction, the thin-film semiconductor is displaced corresponding to the fluid pressure, so that it can be used as a pressure sensor.

[0003] Most noticeable is a fixed comb-teeth electrode formed on a substrate in such a manner that a conductive thin-film semiconductor in which a movable comb-teeth electrode is integrally continuous is engaged with a gap with the movable comb-teeth electrode. By applying a pulsed voltage between the thin film semiconductor and the thin film semiconductor, excitation is performed in the x direction parallel to the substrate surface, and the angular velocity about the y-axis parallel to the substrate surface is applied to the thin film semiconductor. Axis (vertical axis)
This is an angular velocity sensor that detects the displacement (amplitude) of the vibration in the direction with a detection electrode on the substrate facing the thin film semiconductor in the z direction (for example, JP-A-7-218268). Also, x
Displacement (amplitude) of thin film semiconductor vibration in the y direction due to the application of angular velocity about the z axis to the thin film semiconductor vibrating in the direction
There is also an angular velocity sensor which detects the following with a detection electrode facing the thin film semiconductor in the y direction.

FIG. 16 shows an example in which the conductive thin-film semiconductor 17 is excited in the x-direction, and the amplitude (displacement) of the vibration of the thin-film semiconductor 17 in the z-direction caused by the application of an angular velocity about the y-axis to the detection electrode 4. FIG. 17 is a cross-sectional view taken along line AA of FIG.
The line cross section is shown in FIG. On the silicon substrate 1 on which the insulating film 2 is formed, a floating body anchor 16, made of polysilicon (hereinafter referred to as conductive polysilicon) containing an impurity for making it conductive, is used.
The fixed electrode 20 and the detection electrode 4 are fixed. A floating body (thin film movable body) 17, which is a semiconductor thin film made of conductive polysilicon, is separated upward from the insulating film 2 and is supported by supporting beams 14 and 15 integral with the floating body 17 and also through a floating body anchor. It is supported by the substrate 1 via the insulating film 16 and the insulating film 2. The floating body 17 includes a support beam and a floating body anchor 16.
Is connected to the electrode pad by a wiring 6 formed on the insulating film 2. The fixed electrode 20 has the same wiring 3
The detection electrode 4 is connected to the electrode pad by the wiring 5.

[0005] A floating support beam 15 extending in the y direction and a continuous floating support beam 14 extending in the x direction are connected to the floating body anchor 17.
It is floatingly supported on the substrate 1.

[0006] A plurality of movable comb-teeth electrodes 18 for x driving protrude from the floating body 17 to the left and right (x direction) in a comb-like shape at equal pitches in the y direction. The fixed electrode 20 includes a comb-shaped fixed comb-tooth electrode 19 for driving x, which has entered the interdental slot of the movable comb-tooth electrode 18. There is a small gap between the movable comb electrode 18 for x drive and the fixed comb electrode 19 for x drive.

On the insulating film 2 on the substrate 1, there is a rectangular body of the floating body 17 and a detection electrode 4 which faces the surface with a small gap, and the wiring 5 is continuous with this.

The above-mentioned floating support beams 14, 15 and floating body 1
7 (and its movable comb electrode 18) and fixed electrode 20
Of the substrate 1 (from the surface of the insulating film 2 above)
Away in direction. That is, it faces the surface of the substrate 1 with a gap. These are formed integrally and continuously on the floating body anchor and the fixed electrode electrode pad after forming the floating body anchor and the fixed electrode pad on the surface of the silicon substrate 1 by the micro-machining technology. As described above, a support mode that is away from the surface of the substrate 1 in the z direction and that can be displaced or bent in the x direction, the y direction, or the z direction with respect to the substrate 1 is referred to as “floating” or “movable” in this document.

The floating support beams 14, 1 for supporting the floating body 17
Since 5 is floating from the base 1 and the support beam 15 extends in the y direction, it does not bend in the y direction, but easily bends in the x direction, and the floating body 17 easily vibrates in the x and z directions.

The floating body 17 is connected to an x drive circuit (not shown) via the floating support beams 14, 15, the anchor 16, and the wiring 6, and is connected to an equipment ground (GND) there. The pair of fixed electrodes 20 facing each other with the floating body 17 interposed therebetween are connected to the x drive circuit via the wiring 3 and the electrode pad 21. The x drive circuit alternately applies a high voltage to each of the pair of fixed electrodes 20, and repeats this. The floating body 17 is pulled to the right in FIG. 1 when a high voltage is applied to the fixed electrode on the right side, and is pulled to the left when a high voltage is applied to the fixed electrode on the left side. That is, it vibrates in the x direction.

When an angular velocity of rotation about the y-axis is applied to the floating body 17, Coriolis force is applied to the floating body 17,
The floating body 17 has an elliptical vibration that vibrates also in the z direction. The floating body 17 vibrates in the z direction. The floating body 17 is at the equipment earth potential (GND), but the detection electrode 4 is connected to a capacitance detection circuit (not shown). The capacitance detection circuit generates an electric signal indicating the capacitance between the floating body 17 and the detection electrode 4. The level of this electric signal is
7 corresponds to the amplitude of the z-direction vibration. A signal processing circuit (not shown) converts this electric signal into a signal representing angular velocity (angular velocity signal).

The above is the outline of the principle of detecting the angular velocity. FIG.
The micromachine shown in FIG. 6 is, as shown in FIG.
A center line Lcy extending in the y-direction
Symmetrically, two sets are provided. The support beams 14 extending in the x direction of both sets are common and integrally continuous. Both sets of floating bodies (17) are relatively phase-excited and the right floating body is displaced to the left when the left floating body 17 is displaced to the right.
Thereby, when an angular velocity about the y-axis is applied to both floating bodies,
Both floating bodies oscillate relatively in opposite phases in the z direction, and when the left floating body 17 is displaced upward, the right floating body is displaced downward. The signal processing circuit includes: a first electric signal representing a capacitance between the left floating body 17 and the detection electrode 4 opposed thereto;
The second electric signal representing the capacitance between the floating body on the right side and the detection electrode opposed thereto is differentially amplified, and the electric signal obtained by this processing is converted into an angular velocity signal. A first set of angular velocity detection systems (the one on the left side of Lcy) and a second set of angular velocity detection systems (Lcy
The noise commonly applied to the right side of cy is canceled by the differential amplification, and an angular velocity signal having a high S / N is obtained.

[0013]

However, the electrostatic force between the wiring 5 of the detection electrode 4 of the micromachine and the floating body (14, 15, 17, 18; in particular, the support beam 14 crossing over the wiring 3). Unnecessary force acts on the floating body due to the attraction, which causes a decrease in the S / N ratio. In particular, the substrate is driven in the x-direction parallel to the substrate, the y-direction parallel to the substrate and perpendicular to the driving direction is used as a detection axis of the angular velocity, and the detection of the angular velocity is z perpendicular to the substrate induced by Coriolis force. In the case of the angular velocity sensor shown as an example as described above for detecting vibration in the direction, the floating body (14, 15, 17, 1)
8) Fixed electrode 2 placed on substrate with a gap
In addition to the noise due to the capacitive coupling between the zero and the detection electrode 4, between the wiring 3 of the fixed electrode 20 and the floating body (14, 15, 17, 18: especially 14), the electrostatic force in the z direction with respect to the substrate An attractive force acts on the floating body to induce a z-direction vibration corresponding to the x excitation frequency. In the case of the above-described vibration type angular velocity sensor, the frequency of the z-direction vibration caused by the above-mentioned electrostatic attraction induced in the vibration direction z generated by the angular velocity is the same as the frequency of the x excitation, so that the noise due to the above-described capacitive coupling, and The vibration induced by the above-mentioned electrostatic attraction appears as an offset of the angular velocity detection signal of the sensor, and causes a decrease in the angular velocity detection accuracy of the sensor.

Further, when the floating body is excited in the x direction in a plane parallel to the substrate, and the angular velocity about the z axis perpendicular to the substrate acts on the floating body, the vibration in the y direction induced by Coriolis force In the angular velocity sensor which detects the floating body, the wiring of the drive electrode (20) exists below the floating body, so that the drive electrode (20) and the detection electrode for detecting the y-direction vibration of the floating body are capacitively coupled. In addition to the noise, a vibration in a direction perpendicular to the substrate is induced in the floating body, and the relative position between the floating body and the detection electrode changes, which becomes noise and degrades S / N.

The first object of the present invention is to prevent deterioration of S / N due to capacitive coupling between a wiring on a substrate and a detection element.
It is a second object of the present invention to prevent a decrease in physical quantity detection accuracy due to an electrostatic attraction between a wiring on a substrate and a thin film movable body.

[0016]

[Means for Solving the Problems]

(1) The present invention relates to a substrate (1, 2), a thin film movable body (14, 15, 17, 18), which is arranged substantially parallel to the substrate with a gap.
In a micromachine sensor having an element (20) supported by the substrate for detecting the displacement of the thin film movable body and an electric wiring (3, 5) on the substrate, the electric wiring (3,
A micromachine sensor comprising: a conductive film (8) for covering 5) at an insulating distance. In addition, in order to facilitate understanding, the reference numerals of the corresponding elements of the embodiment shown in the drawings and described later are added in the parentheses for reference.

According to this, the conductive film (8) is connected to the electric wiring (3, 3).
Since (5) is electrically shielded, deterioration of S / N due to capacitive coupling between the electric wiring (3, 5) and the element (20) is reduced. In addition, the wiring (3,5) on the substrate and the thin film movable body (14,15,17,1)
8), the accuracy of physical quantity detection does not decrease due to electrostatic attraction.

[0018]

BEST MODE FOR CARRYING OUT THE INVENTION

(2) A micromachine sensor in which the conductive film is connected to a constant potential. As a result, the shielding effect is more reliable, and the detection accuracy can be improved.

(3) A micromachine sensor in which the conductive film has the same potential as the thin-film movable body. Thereby, the electrostatic attraction acting on the thin film movable body in the direction of the substrate can be minimized, the operation of the sensor is stabilized, and the accuracy can be improved.

(4) Substrates (1, 2) and thin-film movable bodies (14, 15, 17, 1
8) an element (4) supported by the substrate for detecting the displacement of the thin-film movable body, and a wiring (5) on the substrate connected to the element, wherein the wiring (5 )).
4,15,17,18) A conductive film located between the portion facing 14) and the thin-film movable body with an insulating distance between them.
(8) A micromachine sensor comprising: According to this, the deterioration of S / N due to the capacitive coupling between the electric wiring (5) and the element (20) via the thin film movable body (14, 15, 17, 18) is reduced.

(5) Substrates (1, 2), and thin film movable members (14, 15, 17, 1
8) a micromachine sensor having an element (20) supported by the substrate for driving the thin-film movable body to vibrate, and a wiring (3) on the substrate connected to the element (20); At least the thin film movable body (1) of (3)
4,15,17,18) A conductive film located between the portion facing 14) and the thin-film movable body with an insulating distance between them.
(8) A micromachine sensor comprising:

According to this, the physical quantity detection accuracy does not decrease due to the electrostatic attraction between the wiring (3) on the substrate and the thin film movable body (14, 15, 17, 18).

(6) Substrates (1, 2), and thin-film movable members (14, 15, 17, 1
8) an element (20) supported by the substrate for driving the thin-film movable body to vibrate, and an element for detecting the displacement of the thin-film movable body (14, 15, 17, 18 and 17) supported by the substrate. In a micromachine sensor having an element (4) and a wiring (3, 5) on a substrate connected to the element (20, 4), at least the thin film movable body of the wiring (3, 5) is provided.
(14, 15, 17, 18 of 14) between the portion facing the thin film movable body and the conductive film located at an insulating distance from both
(8) A micromachine sensor comprising:

According to this, the electric wiring (5) and the element
The deterioration of S / N due to capacitive coupling with (20) through the thin film movable body (14, 15, 17, 18) is reduced. Wiring on board (3)
There is no decrease in physical quantity detection accuracy due to electrostatic attraction between the thin film movable body (14, 15, 17, 18).

(7) The conductive film (8) comprises the wiring (3,5)
Located substantially over the entire length of the substrate.

Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention is shown in FIG.
FIG. 2 shows a line cross section, and FIG. 3 shows a line BB cross section. This embodiment is obtained by improving the conventional single angular velocity sensor shown in FIG. 16 and described above based on the present invention.
In FIG. 3, the structures of floating bodies 14, 15, 16, 17, 18, fixed electrodes 19 and 20, wirings 3, 5, and 6 are the same as those of the conventional angular velocity sensor (FIG. 16), and the operation principle is the same. The angular velocity is detected based on the principle. Therefore, the description of these elements is omitted here, and the improved portion will be described. The conductive layer 8 and the insulating film 7 are combined with the floating bodies 14, 15,.
The electric field from the wiring was shielded by the conductive layer 8 by being inserted between the wirings 17 and 18 and the wirings 3, 5, and 6. As a result, unnecessary force is not applied to the floating body 17, and highly accurate detection is possible. In addition, the conductive layer 8 serves as a shield against disturbance with respect to the detection wiring 5, and the S / N ratio is improved. Next, an example of a manufacturing process of the sensor shown in FIG. 1 will be described.

1) Substrate 1 A single crystal Si substrate is used as the substrate 1. The substrate 1 is made of Si
A polycrystalline substrate, a glass substrate, or a stainless steel substrate may be used.

2) Formation of Insulating Film 2 An SiN film is formed as the insulating film 2 by plasma CVD.
0 nm is formed. If an insulating substrate is used,
The insulating film 2 need not be formed. Further, the thickness of the insulating film 2 is not limited to 100 nm. As the insulating film 2, a Si oxide film, an Al ₂ O ₃ (aluminum oxide) film, or an AlN (aluminum nitride) film may be used. As a film forming means, thermal CVD, sputtering, or the like may be used instead of plasma CVD. After the film formation, a heat treatment at, for example, 1000 ° C. for about 30 minutes may be performed.

3) Formation of detection electrode 4 and wirings 3, 5, and 6 (FIG. 4) Five layers of n-type polycrystalline Si (polysilicon) are formed by thermal CVD.
The detection electrode 4, the fixed electrode 20, and the floating body anchor 1 are formed by photolithography and etching.
Wirings 3, 5, and 6 for connecting 6 to electrode pad 21 (FIG. 4)
To form

The polycrystalline Si may be formed by plasma CVD, sputtering, or the like. The doping of the n-type impurity may be performed simultaneously with the film formation, or may be performed by ion implantation or thermal diffusion after the film formation. The thickness is not limited to 500 nm, and may be amorphous Si at the time of film formation. A group V element (P, As, Sb, etc.) is used as the n-type impurity. Further, a p-type semiconductor thin film may be used for the semiconductor thin films (3 to 6), but all the semiconductor thin films formed in the subsequent steps are p-type. n
100 after the formation of the n-type Si thin film or after the introduction of the n-type impurity
Heat treatment at 0 ° C. for about 30 minutes may be performed. RIE in wet etching of the etching step HF-HNO ₃ -H ₂ O system, or by dry etching using an ECR plasma etching or the like. FIG. 4 shows the upper surface of the substrate 1 after the etching.

4) Formation of Insulating Film 7 An SiN film is formed as the insulating film 7 by plasma CVD.
0 nm is formed. Note that the thickness of the insulating film 7 is 100 nm.
Not limited to Si oxide film, Al ₂ O as insulating film 7
_Three films and an AlN film may be used. As a film forming means, thermal CVD, sputtering, or the like may be used instead of plasma CVD.
Preferably, SiN, BSG (Boro-Silicate-Glass), etc.
An insulating film having a high selectivity with respect to the etching layer 9 to be added later is formed to a thickness equal to or greater than the thickness of the Si thin film layer. After the film formation, a heat treatment at, for example, 1000 ° C. for about 30 minutes may be performed.

5) Formation of conductive layer 8 covering wiring (FIG. 5) 500 nm of n-type polycrystalline Si is formed by thermal CVD.
By photolithography and etching processes, at least regions of the detection electrode 4, the fixed electrode 20, the anchor 16, and the like are removed. The polycrystalline Si may be formed by plasma CVD, sputtering, or the like. The doping of the n-type impurity may be performed simultaneously with the film formation, or may be performed by ion implantation or thermal diffusion after the film formation. The thickness of the thin film is not limited to 500 nm, and may be amorphous Si at the time of film formation. A group V element (P, As, Sb, etc.) is used as the n-type impurity. When the detection electrode 4 and the wirings 3, 5, and 6 are p-type semiconductor thin films, the conductive layer 8 is of p-type. After the formation of the n-type Si thin film or the introduction of the n-type impurity, heat treatment may be performed at 1000 ° C. for about 30 minutes. Etching process is HF-HNO
₃ -H ₂ O system RIE either wet etching may be dry etching using an ECR plasma etching or the like. FIG. 5 shows a state where regions such as the detection electrode 4, the fixed electrode 20, the anchor 16 and the like are opened in the conductive layer 8 by etching.

6) Etching of insulating film 7 (FIG. 6) The detection electrode 4 is formed by photolithography and etching.
Is removed, and the detection electrode 4 is exposed. Note that the etching process can be performed by RIE, EC even in wet etching of HF-NH ₄ F-H ₂ O (BHF: buffered hydrofluoric acid).
Dry etching using R plasma etching or the like may be used. FIG. 6 shows a state in which the detection electrode 4 in the region (insulating film 7) opened in the conductive layer 8 is etched to expose the detection electrode 4.

7) Formation of Etching Layer 9 (FIG. 7) As the etching layer 9, PSG (Phospho
-Silicate-Glass) is formed to have a thickness of 2 μm, and a contact hole of the anchor 16 of the floating body 17, a contact hole 10 of the fixed portion of the fixed electrode 20, and a contact hole 11 of the electrode pad 21 are formed. The part 12 is exposed.

The thickness of the etching layer 9 is not limited, but is preferably not less than the sum of the thicknesses of the lower wirings 3, 5, and 6, and the thicknesses of the insulating film 7 and the conductive layer 8. Further, as the film formation method, a method other than thermal CVD may be used as in the case of the insulating films 2 and 7, and the contact hole etching step is performed by H
_{F-NH 4 F-H 2} O system (BHF: Buffered HF)
Wet etching or dry etching using RIE, ECR plasma etching or the like.

8) Floating body (14, 15, 17, 18) and fixed electrode
(19, 20) (FIG. 8) As the floating body (14, 15, 17, 18), the fixed electrode (19, 20) and the semiconductor thin film 13 in the form of an electrode pad, n-type polycrystalline Si is formed by thermal CVD. Is formed to a desired film thickness, and floating bodies (14, 15, 17, 18),
Semiconductor thin film 1 in the form of fixed electrodes (19, 20) and electrode pads
Work into 3 shape.

The sensor shown in FIG. 1 to be manufactured excites the floating body 17 in the x direction parallel to the substrate 1 and detects the vibration induced in the z direction perpendicular to the substrate 1 by the detection electrode 4. Generate an angular velocity signal. In a vibration type angular velocity sensor of this type, the z frequency of the floating body is set to a frequency having a difference of about 100 Hz with respect to the resonance frequency of x excitation of 10 to 20 kHz.
It is necessary to set the resonance frequency in the direction, and the film thickness of the floating body has almost no effect on the resonance frequency of the x excitation, but the resonance frequency in the z direction greatly depends on the film thickness of the floating body. It is necessary to control the thickness of the body with high precision.

The polycrystalline Si is formed by plasma CV
D, sputtering or the like may be used, and the doping of the n-type impurity may be performed simultaneously with the film formation, or after the film formation, ion implantation or thermal diffusion may be used. Note that amorphous Si may be used during film formation. The n-type impurity includes a group V element (P, As, Sb).
Etc.). Further, the detection electrode 4 and the wiring 3,
When 5, 6 are p-type semiconductor thin films, floating bodies (14, 15, 17,
18), the fixed electrodes (19, 20), and the semiconductor thin film 13 in the form of an electrode pad are p-type. In addition, RI is used in the etching process.
E, Anisotropic dry etching using ECR plasma etching or the like is preferable. FIG. 8 shows a state in which the formation of functional elements such as a floating body has been completed.

9) Formation of Electrode Pad 21 (FIG. 9) An Al (aluminum) thin film is formed by vapor deposition, and the electrode pad 21 is formed by photolithography and etching. Sputtering may be used to form the Al thin film. The etching may be wet etching using a phosphoric acid-based etchant or dry etching using RIE, ECR plasma etching, or the like. Further, the electrode pads 21 may be formed using a lift-off method. C in addition to Al
A single-layer or multilayer film of a metal such as r, Au, W, and Mo may be used.

10) Removal of etching layer 9 (FIG. 1) The etching layer 9 is removed with a hydrofluoric acid-based etchant (hydrofluoric acid or buffered hydrofluoric acid). As an etching method, isotropic dry etching using RIE, ECR plasma etching, or the like may be used. When the etching layer 9 is removed, the angular velocity sensor shown in FIG. 1 is obtained.

An angular velocity signal can be obtained by connecting a drive circuit and a detection circuit to the sensor manufactured through the above steps.

In the portion corresponding to the contact hole for the floating body anchor opened in the etching layer 9 in the above 7), the floating body
(14, 15, 17, 18) are connected to the wiring 6 and correspond to the contact holes 10 for the fixed electrodes.
Are connected to the wiring 3 and the detection electrode 4 is formed integrally and continuously with the wiring 5 when forming the wiring, and these are connected to the electrode pad 21 at the site of the contact hole for the electrode pad. Therefore, the floating bodies (14, 15, 17, 18), the fixed electrodes (19, 20), the detection electrode 4, and the conductive layer 8 are electrically connected to each of the electrode pads 21. The removal of the etching layer 9 exposes the conductive layer 8 covering most of the area of the substrate 1, and this conductive layer 8 and the floating body (14, 15, 1)
7, 18) and the fixed electrodes (19, 20) have a gap corresponding to the thickness of the etching layer 9 described above.

FIG. 10 shows an outline of an angular velocity detecting circuit connected to the angular velocity sensor shown in FIG. The left floating body 17 and the right floating body are connected to the x drive circuit 31, where they are connected to the equipment ground (GND). The conductive layer 8 is also connected to the equipment ground (GND).

The pair of fixed electrodes 20 on the left and the pair of fixed electrodes on the right are also connected to the x drive circuit 31. The x drive circuit 31 has substantially the same phase and the same voltage for the left pair of fixed electrodes 20 on the right side of the left floating body and the right pair of fixed electrodes on the left side of the right floating body. Is applied. Further, a rectangular wave voltage having substantially the same phase and the same voltage is provided on the left pair of fixed electrodes 20 on the left side of the left floating body and on the right pair of fixed electrodes on the right side of the right floating body. Apply VD2.
The rectangular wave voltages VD1 and VD2 are 1 as shown in FIG.
The phase is shifted by 80 degrees (opposite phase). As a result, the left floating body 17 and the right floating body vibrate in the x direction with a relatively opposite phase.

When an angular velocity about the y-axis is applied to both floating bodies,
Both floating bodies oscillate in the z-direction, relatively out of phase. As a result, the capacitance between the left floating body 17 and the detection electrode 4 opposing the same fluctuates, and the capacitance between the right floating body and the detection electrode opposing it fluctuates in the opposite phase. Vibrate. The capacitance detection circuit 32 includes a first electric signal representing the capacitance between the left floating body 17 and the detection electrode 4 opposed thereto, and a capacitance between the right floating body 17 and the detection electrode opposed thereto. When a z-vibration detection signal is generated by differentially amplifying the second electric signal representing the z-direction and the above-described vibration in the x-direction is constant, there is a certain relationship between the angular velocity and the z-vibration detection signal. The signal processing circuit 33, based on this relationship,
The z-vibration detection signal is converted into a signal representing angular velocity (angular velocity signal).

FIG. 11 shows the voltages VD1 and VD2 applied to the fixed electrode (20) by the x drive circuit 31 as described above, and the x vibration (displacement in the x direction) of the left floating body 17 and the right floating body.
And the relationship between the x vibration and the z vibration when an angular velocity is applied. Depending on the direction of the angular velocity (clockwise / counterclockwise), the phase of the z vibration detection signal is shifted by 180 degrees (thick line and thin line of z displacement in FIG. 11). The signal processing circuit 33 determines the direction (clockwise / counterclockwise) of the angular velocity based on the phase difference of the z vibration detection signal from the capacitance detection circuit 32 with respect to the x excitation, and a direction signal indicating the direction. and an angular velocity value signal representing the absolute value of the angular velocity corresponding to the amplitude of the z vibration detection signal.

The conductive layer 8 covers all of the wirings 3, 5, 6 on the substrate 1 via the insulating film 7, and the distribution area of the movable comb electrode 19 of the floating body and the fixed comb electrode 18 of the fixed electrode. Of the wirings 3, 5, 6, and the floating body (14, 15, 17, 18) and the detection electrode 4 have a shielding effect against external noise. high. In addition, the driving voltage (VD
1, VD2) greatly reduces the electrostatic induction voltage (induction noise). Furthermore, the fixed electrode wiring 3 and the floating body (14, 1
5, 17 and 18), the conductive layer 8 exists between
The electrostatic attraction in the z direction due to the potential fluctuation (VD1) of the wiring 3 does not act between the floating body and the floating body.

In order to increase the excitation efficiency of the floating body,
Preferably, the frequency of the x excitation is automatically adjusted to the resonance frequency of the x vibration of the floating body. In such a case, as is conventionally done, the floating body (14, 15, 17, 18)
A displacement detecting structure for detecting displacement in the direction is added, and an x vibration detection signal of the floating body is fed back from the capacitance detecting circuit 34 to the x driving circuit 31. As the displacement detecting structure, for example, the same as the combination of the movable comb electrode 18 and the fixed comb electrode 19, or the movable comb electrode 23 shown in FIG.
And the same as the combination of the fixed comb electrode 22 (FIG. 1
3, the x-axis and the y-axis are interchanged). When the x-vibration detection signal is fed back to the capacitance detection circuit 34, the x-drive circuit 31 sets the above-mentioned value every time the absolute value of the level of the x-vibration detection signal (AC signal) reaches the set value. The levels of the rectangular wave voltages VD1 and VD2 are switched (rising / falling). This causes the floating body 17 to vibrate in the x direction at a predetermined amplitude.

As a driving method, the capacitance detecting circuit 3
4 is driven at a resonance frequency by PLL (Phase Lock Loop) control using the signal obtained from the control circuit 4, and the drive amplitude is obtained from the signal obtained from the capacitance detection circuit 34. May be controlled to be constant. These enable low-voltage driving with high x excitation efficiency.

FIG. 12 shows a second embodiment of the present invention. In the second embodiment, the substantially rectangular floating body 17 vibrates in the x direction by alternately applying a voltage to the left and right fixed electrodes. When an angular velocity about the z-axis is applied to the floating body 17, the floating body 1
7 also oscillates in the y direction. In the floating body 17, a large number of movable electrodes 23 for detecting y vibration, which are beam-shaped and extend in the x direction, are integrally continuous and are distributed at a predetermined pitch in the y direction. Between adjacent ones of these electrodes 23, there are two sets of fixed electrodes 22A and 22B for detecting y vibration,
Is displaced in the + y direction, the capacitance between the movable electrode 23 and the first set of fixed electrodes 22A increases, and the capacitance between the movable electrode 23 and the second set of fixed electrodes 22B decreases. -Y
When displacing in the direction, the opposite is true. Therefore,
A first electric signal representing the capacitance between the movable electrode 23 and the fixed electrode 22A and a second electric signal representing the capacitance between the movable electrode 23 and the fixed electrode 22B are generated by a capacitance detection circuit (not shown). Then, by differentially amplifying the first electric signal and the second electric signal, an electric signal representing the y vibration of the floating body 17 is obtained. This electric signal is converted into an angular velocity signal by a signal processing circuit (not shown). can do.

In the second embodiment, as in the above-described first embodiment (FIG. 1), substantially the entire surface of the substrate 1 is covered with an insulating film 7, and a conductive layer 8 is provided thereon. 8 is the wiring 3 of the fixed electrode 20 and the fixed detection electrodes 22A and 22B.
Above the wirings 5A, 5B and floating bodies (15, 17, 18, 2
3) and the fixed comb electrode 19 of the fixed electrode and the fixed detection electrodes 22A and 22B. The conductive layer 8 is a device arc.
(GND). Therefore, in the second embodiment, similarly to the first embodiment, the wirings 3, 5A, 5A
B, 6, floating body (15, 17, 18, 23) and detection electrode 22A,
22B has a high shield effect against external noise, and furthermore, noise induced in the detection electrodes 22A and 22B by the electrostatic coupling between the fixed electrode 20 and the fixed detection electrodes 22A and 22B corresponding to the x excitation voltage is small.

FIG. 13 shows a third embodiment of the present invention. In the third embodiment, the floating body 17 can move in the y direction. In the floating body 17, a large number of movable electrodes 23 for detecting y displacement, which are beam-shaped and extend in the x direction, are integrally continuous and are distributed at a predetermined pitch in the y direction. Between the adjacent ones of these electrodes 23, two sets of a large number of fixed electrodes 22A for detecting y displacement,
When the floating body 17 is displaced in the + y direction, the capacitance between the movable electrode 23 and the first set of fixed electrodes 22A increases, and the static electricity between the movable electrode 23 and the second set of fixed electrodes 22B is increased. The capacity decreases. The reverse is true when displacing in the -y direction. Therefore, a first electric signal representing the capacitance between the movable electrode 23 and the fixed electrode 22A and a second electric signal representing the capacitance between the movable electrode 23 and the fixed electrode 22B are generated by a capacitance detection circuit (not shown). Is generated, and the first electric signal and the second electric signal are differentially amplified, whereby an electric signal of a level corresponding to the y position of the floating body 17 is obtained. When acceleration in the direction of arrow 25 (y direction) shown in FIG. 13 is applied to the floating body 17, the floating body 1
7 is displaced. If an electric signal at a level corresponding to the y position of the floating body 17 is converted into an electric signal representing acceleration by a signal processing circuit (not shown), acceleration can be detected.

Also in the third embodiment, substantially the entire surface of the substrate 1 is covered with the insulating film 7 as in the first embodiment.
There is a conductive layer 8 thereon, and this conductive layer 8 is on the wirings 24A, 24B of the fixed detection electrodes 22A, 22B and is floating (15, 17, 23) and the fixed detection electrodes 22A, 2B.
Located below 2B. The conductive layer 8 is a device earth (GN)
D). Therefore, also in the third embodiment, the wirings 24A, 24B3, the floating bodies (15, 17, 23) and the detection electrodes 22A, 22B have a high shielding effect against external noise.

FIG. 14 shows a fourth embodiment of the present invention. This fourth embodiment is similar to the second embodiment shown in FIG.
The floating body 17 of the second embodiment is substantially immovable in the y direction, and the movable comb electrode 18 and the fixed electrode 20 for x excitation are omitted. A first electric signal representing the capacitance between the movable electrode 23 / fixed electrode 22A and a movable electrode 23 / fixed electrode 22
Generating a second electrical signal representing the capacitance between B and
By differentially amplifying the electric signal and the second electric signal,
An electric signal of a level corresponding to the y position of the floating body 17 is obtained. When acceleration in the direction of arrow 25 (y direction) shown in FIG. 14 is applied to the floating body 17, the floating body 17 is displaced in accordance with the acceleration. If an electric signal at a level corresponding to the y position of the floating body 17 is converted into an electric signal representing acceleration by a signal processing circuit (not shown), acceleration can be detected.

In the fourth embodiment, as in the first embodiment, substantially the entire surface of the substrate 1 is covered with the insulating film 7.
There is a conductive layer 8 thereon, and this conductive layer 8 is on the wirings 24A, 24B of the fixed detection electrodes 22A, 22B and is floating (15, 17, 23) and the fixed detection electrodes 22A, 2B.
Located below 2B. The conductive layer 8 is a device earth (GN)
D). Therefore, also in the fourth embodiment, the wirings 24A and 24B, the floating bodies (15, 17, 23) and the detection electrodes 2
2A and 22B have a high shielding effect against external noise.

FIG. 15 shows a fifth embodiment of the present invention. In the fifth embodiment, the floating body 17 can be displaced in the x direction but not in the y direction. The floating body 17 has movable comb electrodes 23 on the left and right, and fixed comb teeth 22 of the left and right fixed detection electrodes 20 project between the teeth. Floating body 17 is + x
When displaced in the right direction, the capacitance between the right movable comb electrode 23 and the right fixed detection electrode 20 increases, and the electrostatic capacitance between the left movable comb electrode and the left fixed detection electrode increases. The capacity is reduced. When displacing in the −x direction (leftward), the opposite is true. Therefore, in a capacitance detection circuit (not shown), the first electric signal representing the capacitance between the right movable comb electrode 23 / the right fixed detection electrode 20 and the first electric signal between the left movable comb electrode / the left fixed detection electrode By generating a second electric signal representing the capacitance of the floating body 17 and differentially amplifying the first electric signal and the second electric signal, an electric signal of a level corresponding to the x position of the floating body 17 can be obtained. When acceleration in the direction of arrow 25 (x direction) shown in FIG. 15 is applied to the floating body 17, the floating body 17 is displaced in accordance with the acceleration. If an electric signal at a level corresponding to the x position of the floating body 17 is converted into an electric signal representing acceleration by a signal processing circuit (not shown), acceleration can be detected. When the fluid flows in the direction of arrow 25 along the surface (plane) of the floating body 17, the floating body 17 moves and is displaced in the direction of arrow 25, and the displacement amount corresponds to the flow velocity of the fluid. If an electric signal at a level corresponding to the x position of the floating body 17 is converted into an electric signal representing the flow velocity by a signal processing circuit (not shown), the flow velocity can be detected.

In the fifth embodiment, as in the first embodiment, substantially the entire surface of the substrate 1 is covered with the insulating film 7.
There is a conductive layer 8 thereon, which is above the wiring 24 of the fixed detection electrode 20 and below the floating bodies (15, 17, 23) and the fixed comb electrode 22. The conductive layer 8 is connected to an equipment ground (GND). Therefore, also in the fifth embodiment, the wiring 24, the floating bodies (15, 17, 23) and the detection electrode 22 have a high shielding effect against external noise.

[Brief description of the drawings]

FIG. 1 is a plan view of a first embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of the angular velocity sensor shown in FIG.

FIG. 3 is a sectional view taken along line BB of the angular velocity sensor shown in FIG.

4 is a plan view of the angular velocity sensor shown in FIG. 1 in the process of being manufactured.

FIG. 5 is a plan view of the angular velocity sensor shown in FIG. 1 in the process of being manufactured.

6 is a plan view of the angular velocity sensor shown in FIG. 1 in the process of being manufactured.

FIG. 7 is a plan view of the angular velocity sensor shown in FIG. 1 in the process of being manufactured.

8 is a plan view of the angular velocity sensor shown in FIG. 1 in the process of being manufactured.

9 is a plan view of the angular velocity sensor shown in FIG. 1 in the process of being manufactured.

FIG. 10 is a block diagram showing a schematic configuration of an electric circuit connected to the angular velocity sensor shown in FIG.

11 is a time chart showing a drive voltage for exciting the floating body of the angular velocity sensor shown in FIG. 10 in x and a displacement amount of the floating body.

FIG. 12 is a plan view of a second embodiment of the present invention.

FIG. 13 is a plan view of a third embodiment of the present invention.

FIG. 14 is a plan view of a fourth embodiment of the present invention.

FIG. 15 is a plan view of a fifth embodiment of the present invention.

FIG. 16 is a plan view of one conventional angular velocity sensor.

FIG. 17 is a sectional view taken along line AA of FIG. 16;

FIG. 18 is a sectional view taken along line BB of FIG. 16;

[Explanation of symbols]

1: substrate 2: insulating film 3: wiring 4: detection electrode 5: wiring 6: wiring 7: insulating film 8: conductive layer 9: etching layer 10: contact hole 11: contact hole 12: contact hole 13: semiconductor thin film 14: Connecting beam 15: beam 16: anchor 17: floating body 18: movable comb electrode 19: fixed comb electrode 20: fixed electrode 21: electrode pad 22A, B:
Fixed detection electrode 23: movable electrode 24: wiring 25: detection direction of acceleration or flow velocity

Claims (3)

[Claims] A substrate, a thin-film movable body provided with a gap with respect to the substrate and arranged substantially parallel to the substrate, an element supported by the substrate for detecting displacement of the thin-film movable body, and an electric wiring on the substrate. A micromachine sensor, comprising: a conductive film that covers the electric wiring with an insulating distance therebetween. 2. The method according to claim 1, wherein the conductive film is connected to a constant potential.
The micromachine sensor according to claim 1. 3. The micromachine sensor according to claim 1, wherein the conductive film has the same potential as the thin film movable body.