JPH07159179A - Vibration type angular velocity sensor - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide a sensor with excellent productivity, low cost, and stable performance. [Configuration] Semiconductor substrate (silicon wafer) 3 for the sensor
A plurality of oscillators 22 formed by anisotropically etching 0 are used. The oscillator 22 has an etching surface [(111)
A p-layer is formed by impurity diffusion with respect to the surface, and a pn junction is formed together with the n-type which is the original substrate. The pn
A reverse voltage is applied to the junction to control it in the off state, and the p-layer and the n-layer (original substrate) of each etching surface 28 of the vibrator are electrically separated and used. A piezoelectric film 23 is formed on the vibrator in order to electrically drive the vibrator and to detect vibration according to the input angular velocity. A driving power source is connected between the driving electrode 25 and the substrate electrode 27 (n layer),
An electrical output generated between the detection electrode 26 (formed on the p layer and electrically connected to the p layer) and the common electrode 29 formed across both tapered surfaces of the vibrator is generated. Taken out.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an angular velocity sensor which can be used for observing / controlling the position and attitude of a flying object, a vehicle, a robot, a human body, etc., and more particularly to an angular velocity sensor which is suitable for being small and inexpensive.

[0002]

2. Description of the Related Art Conventional vibration type angular velocity sensors 1 include a beam type as shown in FIG. 4 and a tuning fork type as shown in FIG. In the case of the beam type, as shown in FIG. 4, as a typical example, the vibrator 2, the supporting member 3 supporting the vibrator 2, the driving piezoelectric element 6a provided perpendicularly to the X-axis, and the driving state of the facing surface thereof are monitored. Piezoelectric element 6b and a piezoelectric element 6 for detection provided on a surface perpendicular to the Y-axis
It is composed of c. Piezoelectric element 6 (6a, 6b, 6c)
Is an electrode 5 (5) on the surface of the piezoelectric body 4 (4a, 4b, 4c).
a, 5b, 5c) are formed.

When the vibrator 2 is flexurally vibrated in the X-axis direction (ideally, linear vibration), if there is an input angular velocity of Ω in the Z-axis direction, the Coriolis force (F = −F) in the Y-axis direction. 2 mV
Ω; m receives the mass of the oscillator, V is the vibration velocity), and the bending vibration becomes a combined vibration in the X-axis and Y-axis directions, causing beam displacement in an elliptical shape. By detecting the strain (stress) on the surface of the vibrator 2 perpendicular to the Y axis at this time, an output proportional to the Coriolis force, that is, the input angular velocity Ω can be obtained.

The beam 7 for the vibrator is made of a highly elastic material such as elinvar or quartz, a wire such as a piano wire is used as the support member 3, and a piezoelectric ceramic is used as the piezoelectric body 4. FIG. 6 shows a displacement (vibration) state when the input angular velocity Ω is applied in the Z-axis direction when the beam 7 is driven and bending-vibrates in the X-axis direction.

Tuning Fork Type As a typical example, as shown in FIG. 5, a tuning fork type vibrator 2 and a driving piezoelectric element 6 a and a monitoring piezoelectric element 6 b are provided on each vibrating piece of the tuning fork type vibrator 2, and the vibration direction of the tuning fork 8 is It is formed by a structure having a plate-shaped supporting member 9 which can be bent in the same direction and a piezoelectric element 6c for detection thereon.

As shown in FIG. 7, when the input angular velocity Ω is entered in the direction perpendicular to the vibration of the tuning fork 8 (Z-axis direction), the vibrating pieces of the tuning fork 8 vibrate in opposite directions. A bending moment is generated in the support member 9 supporting 8 and the support member 9 is bent, and the strain (stress) on the support member 9 at that time is detected by the piezoelectric element 6c to output an output proportional to the input angular velocity Ω. Is obtained.

FIG. 7 shows a displacement (vibration) state when the input angular velocity Ω is applied in the Z-axis direction while the tuning fork 8 is driven and vibrates in the X-axis direction.

[0008]

As described above, there are roughly two types of conventional angular velocity sensors, beam type / tuning fork type. In the case of the beam type, it was necessary to separately manufacture the supporting member and the vibrator and assemble them by spot welding or adhesion. Further, the piezoelectric element also requires a step of adhering it by adhesion or the like after the beam is produced, and there is a drawback that it is difficult to simultaneously produce a plurality of beams.

In the case of the tuning fork type as well, there are drawbacks that it is difficult to manufacture a plurality of pieces at the same time because the assembling of the piezoelectric element and the processing of the tuning fork are three-dimensional, and it is necessary to individually adjust. The present invention eliminates the drawbacks of the prior art, and allows a plurality of pieces to be manufactured simultaneously and accurately without assembling them individually.
In other words, it is intended to provide an angular velocity sensor which is excellent in productivity, inexpensive, and stable in performance.

[0010]

[Means for Solving the Problems]

(1) The invention of claim 1 is a vibration type angular velocity sensor configured by using a vibrator formed by anisotropically etching a semiconductor substrate, wherein the vibrator is a surface formed by the etching. A pn junction is formed inside the oscillator by diffusing impurities into the resonator, and a reverse voltage is applied to the pn junction from the outside to electrically turn off the pn junction. And a lower semiconductor substrate portion can be electrically separated.

(2) The invention of claim 2 is the vibration-type angular velocity sensor according to claim 1, wherein a plurality of the vibrators are provided. (3) According to the invention of claim 3, in the vibration type angular velocity sensor according to (1) or (2), vibration of the oscillator is detected for electrically driving the oscillator and according to an input angular velocity. In order to do so, the piezoelectric film is formed on the vibrator.

(4) The invention of claim 4 is the vibration type angular velocity sensor according to any one of (1) to (3), wherein a silicon wafer having a plane orientation (100) is used as the semiconductor substrate, As the etching surface (111)
The surface is what is used.

[0013]

The angular velocity sensor of the present invention is constructed by using a vibrator in which a semiconductor substrate is formed by anisotropic etching. Impurities are diffused into the surface of the oscillator formed by etching to form a pn junction inside the oscillator, and a reverse voltage is applied to the pn junction from the outside to control it electrically off. Thus, the vibrator has a structure in which the central substrate portion and the etching surface can be electrically separated, so that a plurality of angular velocity sensors can be simultaneously manufactured on the semiconductor substrate (wafer). Further, anisotropic etching of a semiconductor substrate can be processed with high precision, so that variations in each sensor can be suppressed, which is suitable for mass production.

[0014]

Embodiments of the present invention will now be described with reference to the drawings. FIG. 1 shows an embodiment of the present invention. FIG. 2 shows an outline of the manufacturing process. FIG. 3 shows an embodiment when the method of supporting the vibrator is different. The semiconductor substrate used is a (100) n-type silicon wafer. Surface 28 formed by etching
Is the (111) plane and has an angle of 54.7 deg with respect to the substrate surface [(100) plane]. By diffusing impurities into the etching surface (111) 28 of the oscillator 22, a p layer is formed on the side surface [etching surface (111)] of the oscillator 22, and a pn junction is formed with the n layer of the semiconductor substrate itself. Then, a reverse voltage is applied to the pn junction from the outside to control the pn junction to be in the off state, and the etching surface 28 and the substrate 30 (inside the vibrator) below the pn junction are electrically separated.

A piezoelectric film (zinc oxide) 23 is formed on the side surface of the vibrator 22 and at least one substrate surface 6 [(100) surface] by sputtering to form a piezoelectric element, which is used for driving and detection. FIG. 2 shows an example of the manufacturing process.
(1) The silicon wafer 30 is thermally oxidized to form the oxide film 24, and then patterned to be used as a mask for anisotropic etching. (2) Anisotropic etching is performed until silicon becomes a diaphragm state. (3) Impurities (boron) are diffused on the etching surface to form a p layer (diffusion layer) 34.
(4) An electrode film 33 for extraction from the p-layer 34 on the side surface of the vibrator is provided using a mechanical mask. (5) The oxide film 24 is patterned to provide a substrate electrode from the back side.
(6) A metal film (chrome etc.) 31 is formed on the back surface, and (7)
Pattern. (8) by sputtering or the like to form a protective film (Si0 ₂ film) 32 on the rear surface is subjected to (9) patterning. (10) Anisotropic etching of silicon is performed from the back side. (11) The protective film 32 on the back surface and the protective film 32 at a portion not protected by the metal film 31 are removed by etching by RIE (Reactive Ion Etching) or the like. (12) The metal film 31 is removed. (1
3), (14) A piezoelectric film (zinc oxide, etc.) 23 is formed on the front and back surfaces of the vibrator 22 by sputtering. (1
5), (16) common electrode film 29 and driving electrode film 25
Are formed on the front surface and the back surface of the vibrator 22 using a mechanical mask.

In FIG. 1, since the detection electrode 26 is formed on the diffusion layer (p layer) formed on the tapered surface (etching surface), it is electrically connected to the p layer. The substrate electrode 27 is directly formed on the silicon wafer without the oxide film 24, and is electrically connected to n-type silicon. While using the sensor, the detection electrode 26 (p layer) and the substrate electrode 27
A reverse voltage is maintained between (n layer) and the pn junction is controlled to be off. A drive power source is connected between the drive electrode 25 and the substrate electrode 27, and the detection electrode 26 (p layer)
The output voltage generated between the common electrode 29 and the common electrode 29 is taken out.

In the above description, the p-type semiconductor substrate is an n-type semiconductor substrate.
Although the type diffusion layer is provided, the n type diffusion layer may be provided on the p type semiconductor substrate.

[0018]

As described above, according to the present invention, the oscillator 22 formed by anisotropically etching the semiconductor substrate 30 is used, and the surface 2 formed by etching the oscillator 22.
8 to form a pn layer inside the vibrator, and a reverse voltage is applied between the pn layers from the outside to electrically control the vibrator 22 to be turned off. By having a structure in which the portion of the substrate 30 (inside the vibrator) and the etching surface 28 can be separated,
A plurality of angular velocity sensors can be simultaneously manufactured on the semiconductor substrate (wafer) 30. Further, since anisotropic etching of the semiconductor substrate 30 can be processed with high precision, it is possible to suppress variations in each sensor, which is suitable for mass production.

In the conventional oscillator, the drive electrode 5a, the monitor electrode 5b, and the detection electrode 5c must be separately formed on each side surface with the beam body having a common potential and the piezoelectric film sandwiched on each side surface. There wasn't. Therefore, it is difficult to fabricate electrodes on each surface separately through a mechanical mask so as not to connect with the electrodes on other surfaces, and it is difficult to fabricate the position and area of the electrodes that directly affect the performance with high accuracy. There was a problem.

In the present invention, since the substrate (n layer) of the vibrator and the diffusion layer (p layer) on each tapered surface are electrically separated,
The common electrode 29 via the piezoelectric film can have a common potential. Therefore, the electrode manufactured through the mechanical mask needs to be electrically connected to each of the n and p layers formed inside each tapered surface, but the effect of the positional accuracy on the performance should be almost eliminated as compared with the conventional example. You can

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of the present invention, in which A is a plan view and B is a plan view.
Is a sectional view taken along aa, and C is a bottom view.

FIG. 2 is a diagram showing the first half of the manufacturing process of the embodiment of FIG.

FIG. 3 is a diagram showing the latter half of the manufacturing process of the embodiment of FIG.

FIG. 4 is a view showing another embodiment of the present invention, in which A is a plan view, B is a sectional view taken along line aa, and C is a bottom view.

5A and 5B are views showing a conventional beam type angular velocity sensor, in which A is a perspective view and B is a sectional view.

6A and 6B are views showing a conventional tuning fork type angular velocity sensor, in which A is a perspective view and B is a plan view.

7 is a principle diagram showing a vibration mode when an input angular velocity Ω is applied in the Z-axis direction while the beam type angular velocity sensor in FIG. 5 is flexibly vibrating in the X-axis direction.

8 is a principle diagram showing a vibration mode when an input angular velocity Ω is applied in the Z-axis direction while the tuning fork type angular velocity sensor of FIG. 6 is vibrating in the X-axis direction.

Claims (4)

[Claims] 1. A vibration-type angular velocity sensor configured using a vibrator formed by anisotropically etching a semiconductor substrate, wherein the vibrator vibrates due to impurity diffusion with respect to a surface formed by the etching. A pn junction is formed inside the child, and a reverse voltage is applied to the pn junction from the outside to electrically turn off the pn junction, so that the etching surface above the pn junction of the oscillator and the semiconductor below A vibration-type angular velocity sensor having a structure capable of being electrically separated from a substrate portion. 2. The vibration type angular velocity sensor according to claim 1, wherein a plurality of the vibrators are provided. 3. The vibration-type angular velocity sensor according to claim 1, wherein a piezoelectric film is used to vibrate in order to electrically drive the vibrator and to detect vibration of the vibrator in accordance with an input angular velocity. It is characterized in that it is formed in the child. 4. The vibration type angular velocity sensor according to claim 1, wherein a silicon wafer having a plane orientation (100) is used as the semiconductor substrate, and a (111) plane is used as an etching surface thereof. Is characterized by.