JP2000131074A - Electrostatically driven angular velocity-detecting apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the S/N in detecting vibrations of an electrostatically driven angular velocity sensor with a simple electric circuit. SOLUTION: The angular velocity-detecting apparatus comprises a vibrating member supported floating to a substrate 1 so that it can vibrate in x direction and a direction orthogonal to the x direction, driving fixed electrodes 9a and 9b for applying an electrostatic force to excite the member in the x direction, a driving circuit 12, a detecting fixed electrode for converting a y vibration by an angular velocity to an electric signal and, a y vibration-detecting circuit. The driving circuit 12 includes amplitude modulators 12c, 12g for generating x excitation signals VDa, VDb by modulating in amplitude carrier waves of a higher frequency than an x vibration frequency by driving signals SDa, SDb of the vibration frequency, and voltage output means 12e, 12h for generating voltages corresponding to the x excitation signals and impressing the voltages to the driving fixed electrodes 9a, 9b. A detecting circuit 13 includes a low pass filter 13d for extracting a low frequency of the vibration frequency.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention excites a vibration member floatingly supported on a substrate by electrostatic drive, and detects, by electrostatic detection, vibration in a direction perpendicular to the excitation direction due to the application of angular velocity. Angular velocity sensor, regarding the angular velocity detection device using, in particular, although not intended to be limited to this,
The present invention relates to an electric circuit that drives an oscillating member to generate an angular velocity signal.

[0002]

2. Description of the Related Art A typical type of angular velocity sensor has a pair of floating comb electrodes (a left floating comb electrode and a right floating comb electrode) on the left side and one set on the right side of a floating thin film. And two sets of fixed comb electrodes (a left fixed comb electrode and a right fixed comb electrode that mesh with and are parallel to each set of floating comb electrodes in a non-contact manner) as left floating comb electrodes / left fixed comb electrodes. By alternately applying a voltage between the space and the right floating comb electrode / the right fixed comb electrode, the floating thin film vibrates in the x direction. When an angular velocity of rotation about the z-axis is applied to the floating thin film, Coriolis force is applied to the floating thin film, and the floating thin film becomes
An elliptical vibration that vibrates also in the y direction. If the floating thin film is used as a conductor or an electrode is bonded, and a detection electrode parallel to the xz plane of the floating thin film is provided on the substrate, the capacitance between the detection electrode and the floating thin film becomes elliptical oscillation. Vibrates according to the y component (angular velocity component). By measuring the change (amplitude) of the capacitance, the angular velocity can be obtained (for example, Japanese Patent Application Laid-Open Nos. 5-248872, 7-2182
68, JP-A-8-152327, JP-A-9-127148, and JP-A-9-42973.

FIG. 4 of US Pat. No. 5,635,638 shows that a pair of vibrators are connected by a pair of semicircular beams, and each of the vibrators has high flexibility in the vibration direction x. Through the beam,
There is disclosed an angular velocity sensor in which the pair of vibrators are floated and supported by eight anchors.

[0004]

A movable electrode of a drive unit and a movable electrode of a detection unit are formed on a vibrator, and the vibrator is moved in the x direction between the movable electrode of the drive unit and the fixed electrode for driving. Since a pulsating voltage or an AC voltage (for example, a rectangular wave having a DC component) for excitation is applied, driving noise (voltage) is generated in the vibrator by electrostatic induction or electromagnetic induction. Noise is induced in the detection fixed electrode for electrostatically detecting the displacement of the movable electrode of the detection unit,
It flows into the detection circuit. This noise includes noise due to capacitive coupling between the drive electrode and the wiring and between the detection electrode and the wiring and insulation failure. Further, noise generated in the vibrator flows to the substrate via an anchor for fixing the vibrator to the substrate, leaks from the substrate to the detection fixed electrode, and flows into the detection circuit. These noises significantly lower the S / N of the detection circuit.

Normally, the vibration frequency and the frequency of the drive signal are the same, and when the vibration motion is detected and feedback is applied or the angular velocity signal is detected, the drive signal is liable to be mixed into the detection signal. Driving with a sine wave of 駆 動 of the driving frequency or using a differential configuration in the detection system has suppressed the deterioration of the S / N ratio of the detection signal.

However, in the former case, since the difference between the driving frequency and the detection frequency is small, a filter having steep characteristics is required, which leads to an increase in cost and a problem that the phase of the detection signal is shifted. That is, a filter having steep characteristics is required to finally remove noise, and the phase is likely to rotate. In the latter case, it is necessary to design including the electrical differential configuration, and the imbalance of the differential configuration due to manufacturing variations may not be negligible. Particularly, in the case of an angular velocity sensor, since the angular velocity signal is very small, this imbalance cannot be ignored.

To solve these problems, in an angular velocity sensor using micromachine technology, a high-frequency signal is applied to a fixed electrode for detecting vibration, and a potential signal of the vibrator or a current flowing into the vibrator is detected by a voltage signal by a detection circuit. The high-frequency component is extracted by passing the converted signal through a high-pass filter, and the extracted high-frequency signal has a potential change of a signal obtained by the vibrator due to the vibrator approaching / separating from the fixed electrode, that is, an applied voltage. Vibration frequency (low frequency)
Therefore, an attempt has been made to extract a signal having an oscillating frequency through a detection circuit and a low-pass filter because the signal includes an amplitude-modulated signal. (Extraction by a filter) is required, which complicates the circuit and leads to an increase in cost. A first object of the present invention is to increase the S / N of vibration detection, and a second object is to realize this with a relatively simple electric circuit.

[0008]

(1) The present invention relates to a method of manufacturing a semiconductor device in which a substrate can be vibrated in an x direction and a direction orthogonal thereto.
(1) A vibrating member (8/81, 82) floatingly supported on a fixed electrode for driving (9a, 9b) for applying an electrostatic force to the vibrating member for x-direction excitation, A driving circuit (12) for applying a driving voltage, and a direction orthogonal to the x-direction (y
/ z), which detects electrostatic angular vibration corresponding to angular velocity by electrostatic detection and converts it into an electric signal.The fixed angular electrodes (11a, 11b) for detection and a vibration detecting circuit (14), and an electrostatically driven angular velocity detecting device (FIG.
In FIG. 6), the drive circuit (12) is an x-excitation signal (VDa) obtained by amplitude-modulating a carrier having a frequency higher than the vibration frequency of the vibration member in the x direction with the drive signals (SDa, SDb) having the vibration frequency. , VDb), and voltage output means (12e) for generating a voltage corresponding to the x excitation signal (VDa, VDb) and applying the voltage to the drive fixed electrode (9a, 9b). , 12
h).

To facilitate understanding, reference numerals in parentheses for corresponding elements or corresponding items in the embodiment shown in the drawings and described later are added for reference.

According to this, since the voltage applied to the drive fixed electrodes (9a, 9b) for the x-direction excitation has a high frequency, the drive noise generated by the application of the drive voltage is a high frequency. On the other hand, the electric signal (VYa, VYb) representing the angular velocity corresponding vibration generated by the vibration detection circuit (14) is a vibration member (8/81, 82)
Therefore, only the target electric signals (VYa, VYb) can be easily extracted by a low-pass filter or a band-pass filter through which a signal of the vibration frequency passes. The S / N of the electric signal (VYa, VYb) is high. If a filter is used, its cutoff frequency (f
By setting c) higher than the oscillation frequency and lower than the frequency of the carrier wave, the phase rotation of the detection signal by the filter can be suppressed small, and the driving noise can be reliably removed.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (2) The vibration detection circuit (14)
A low-pass filter (14d) for extracting a low-frequency signal (VYa, VYb) corresponding to the vibration frequency of the electric signal detected from the vibration corresponding to the angular velocity of the vibration member (8/81, 82). (3) The apparatus further includes excitation detection fixed electrodes (10a, 10b) for detecting x-vibration of the vibrating member (8/81, 82) and an excitation detection circuit (13); (13) is a low-pass filter for extracting a low-frequency signal (VFBa, VFBb) corresponding to the vibration frequency of the electric signal detected as the displacement of the x vibration of the vibration member (8/81, 82), that is, a feedback signal. (13d)
Wherein the drive circuit (12) shifts the phase of the low-frequency signals (VFBa, VFBb) extracted by the excitation detection circuit (13), and
(SDa, SDb).

A high S / N feedback signal (VFBa, VFB)
b) is obtained, so that the stability of x excitation by feedback control is high, and the reliability of angular velocity detection is improved. (4) The frequency of the carrier wave is 100 times or more the vibration frequency by the drive signals (SDa, SDb). The drive noise can be more easily removed, and the drive noise can be removed with a low-order filter. (5) Drive signal (SDa, SDb) and feedback signal of x vibration
The phase difference of (VFBa, VFBb) is ±
It is within 45deg. By setting it within ± 45 deg, a large amplitude rate of vibration can be obtained, a large amplitude can be obtained with a small driving force, the driving signal can be reduced, the power supply voltage can be reduced, and the driving signal Since the amount of contamination is reduced, a low-order filter can be used for the subsequent filter. (6) The voltage output means (12e, 12h) outputs the x excitation signal (VDa, VD
The drive voltage generated corresponding to b) and applied to the drive fixed electrodes (9a, 9b) is such that the center potential thereof is the same as that of the vibration member (8/81, 82). According to this, the force acting on the vibration member (8/81, 82) at the time of the high potential and the low potential of the drive voltage becomes equal, and an unnecessary mode is included in the vibration of the vibration member (8/81, 82). And the vibration of the vibration member (8/81, 82) in the x-vibration and the angular velocity response is stabilized.

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

[0014]

FIG. 1 shows a first embodiment of the present invention. This embodiment is an angular velocity sensor for detecting an angular velocity applied to the vibrator 8 around the z-axis. On the silicon substrate 1 on which the insulating layer is formed, floating body anchors 2a to 2d of polysilicon containing conductive impurities (hereinafter referred to as conductive polysilicon) are joined. By virtue of the wiring (indicated by the dotted line) formed above, the vibration thin film 6, the vibrator 8, the fixed electrodes 9a, 9b /
10a and 10b are connected to connection electrodes (not shown) on the substrate 1. In addition, using a substrate of conductivity (n) opposite to the conductivity type (p) of the polysilicon as the silicon substrate 1, wiring is formed on the silicon substrate 1 by pn junction, and the wiring and the floating body anchors 2a to 2d are connected to each other. You may join with the anchor part of a connection electrode.

A first set of floating support beams 3a to 3d extending in the y direction are continuous with the floating body anchors 2a to 2d, and parallel beams 4a and 4b are continuous with these support beams 3a to 3d. A rectangular ring-shaped vibrating frame 6, which is substantially parallel to the surface of the substrate 1, is continuous with the second set of floating support beams 5a to 5d extending in the y direction, which are continuous with the parallel beams 4a and 4b.

A side (y side or y side) of the vibration frame 6 parallel to the y direction
A plurality of movable comb-shaped electrodes for x driving protruding from the parallel sides 6b and 6d in the left-right direction (x direction) at equal pitches in the y direction in a comb shape protrude. The pair of fixed electrodes 9a and 9b for x drive facing each other with the y side 6d interposed therebetween include:
has entered the interdental slot of the movable comb electrode on the y side 6d,
There is a comb-shaped fixed comb-teeth electrode for x drive, and there is a minute gap between the movable comb electrode for x drive and the fixed comb tooth electrode for x drive. x-drive fixed electrode 9a,
By alternately applying a voltage to 9b, the vibration frame 6 becomes x
Vibrates in the direction.

A pair of fixed electrodes 10a and 10b for detecting x-vibration that face each other with another y-side 6b interposed therebetween include:
has entered the interdental slot of the movable comb electrode on the y side 6b,
There are comb-shaped fixed comb-teeth electrodes for x-vibration detection, and there is a minute gap between the movable comb electrode for x-vibration detection and the fixed comb-teeth electrode for x-vibration detection. Vibration frame 6 is x
When it vibrates in the direction, the capacitance between the fixed electrodes 10a and 10b and the vibration frame 6 changes in height in opposite phases.

A third set of floating support beams 7a extending in the x direction
7d are connected to the y-side 6b of the rectangular ring-shaped vibrating frame 6,
6d, and the other ends of these support beams are connected to the y of the vibrator 8 in the inner space of the b-shaped ring of the vibrating frame 6.
The sides 8b and 8d are integrally connected. The y-sides 8b and 8d of the vibrator 8 are parallel to the third set of support beams 7a to 7d.
A movable electrode 8e for y displacement detection extending in the x direction is distributed in the y direction, and extends in the x direction from the y sides 8b and 8d. Within one pitch of the distribution of the movable electrodes 8e, there is a pair of fixed electrodes 11a and 11b for detecting y displacement, and each pair is distributed in the y direction.

As described above, the first set of floating support beams 3a to 3d,
Parallel beams 4a, 4b, second set of floating support beams 5a to 5d, vibrating frame 6, third set of floating support beams 7a to 7d, vibrator 8, and comb teeth of fixed electrodes 9a, 9b / 10a, 10b Is
It is separated from the surface of the substrate 1 in the z direction. That is, the substrate 1
, Facing each other with a gap. They are,
After the floating body anchor and the fixed electrode anchor are formed on the surface of the silicon substrate 1 by the micro-machining technology, they are formed integrally and continuously on the floating body anchor and the fixed electrode anchor. As described above, a support mode that is separated 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 shape of the above-mentioned vibration frame 6 is a ro-shaped ring, which is vertically and horizontally symmetrical with respect to the intersection of the two diagonal lines, and the center of gravity is located at the intersection. The vibration frame 6 has a third
The vibrator 8 which is integral and continuous through the set of support beams 7a to 7d is also
It is vertically and horizontally symmetric with respect to the intersection, and the center of gravity is at the intersection.

First set of floating support beams 3 for supporting the vibration frame 6
a to 3d and the second set of floating support beams 5a to 5d
Because they are floating from and extend in the y-direction,
Although it does not bend in the direction, it is easy to bend in the x direction.
Are less likely to vibrate in the y direction and more likely to vibrate in the x direction. Since the vibrator 8 is integral with the vibrating frame 6 and is supported by the vibrating frame 6 via the third set of floating support beams 7a to 7d extending in the x direction, when the vibrating frame 6 vibrates in the x direction. The vibrator 8 also vibrates in the x direction. The third set of floating support beams 7a to 7d does not bend in the x direction, but easily bends in the y direction, and the vibrator 8 hardly vibrates in the x direction with respect to the vibrating frame 6 and vibrates in the y direction. Easy to do. Thus, when an angular velocity about the z-axis is applied to the entire sensor (1 to 11), the vibrator 8 vibrates in the y direction, but the vibration frame 6 does not substantially vibrate in the y direction.

The vibration frame 6 (and the vibrator 8)
It is connected to the x drive circuit 12 via a to 2d and wiring (dotted line) on the substrate 1, where it is connected to the equipment ground (GND). The fixed electrodes 9a and 9b are connected to the x drive circuit 12 via wiring on the substrate 1. The x drive circuit 12 alternately applies a high voltage for electrostatic attraction to the fixed electrodes 9a and 9b and repeats this. The vibration frame 6 (and the vibrator 8) is pulled to the left in FIG. 1 when a high voltage is applied to the fixed electrode 9a, and is pulled to the right when a high voltage is applied to the fixed electrode 9b. Vibrates left and right.

When the vibration frame 6 moves to the left, the capacitance between the movable comb-teeth electrode for detecting x vibration (y side 6b) and the fixed electrode 10b for detecting x vibration decreases. The capacitance between the comb electrode (y side 6b) and the fixed electrode 10a for x vibration detection increases. The opposite is true when moving to the right. The movable comb electrode (y side 6b) is at the equipment earth potential (GND), while the fixed electrodes 10a and 10b are connected to the capacitance detection circuit 13. The capacitance detection circuit 13 generates an electric signal indicating a difference (differential amplification value) in capacitance between the fixed electrodes 10a and 10b for detecting x vibration and the vibration frame 6 (device earth potential GND). To the x drive circuit 12. This electric signal is an AC signal (hereinafter referred to as an x-vibration feedback signal) indicating a level change synchronized with the displacement of the x-vibration of the vibration frame 6. The x drive circuit 12 generates a drive signal using the feedback signal, and applies a drive voltage synchronized with the drive signal to the fixed electrodes 9a and 9b.

When the vibrator 8 vibrates in the y direction, the vibrator 8
The capacitance between the movable electrode 8e and the fixed electrode 11a increases and decreases and vibrates, and the movable electrode 8e and the fixed electrode 11
The capacitance between b and fluctuates. The capacitance detecting circuit 14 is an electric signal (y vibration) representing a difference in capacitance (differential amplification value) of the fixed electrodes 11a and 11b for y vibration detection with respect to the vibration frame 6 (equipment earth potential GND). A detection signal is generated and supplied to the signal processing circuit 15. Vibrator 8
When the x vibration of the (vibration frame 6) is constant, there is a certain relationship between the angular velocity and the amplitude of the y vibration of the vibrator 8. The signal processing circuit 15 converts the y vibration detection signal into a signal representing angular velocity (angular velocity signal) based on this relationship.

FIG. 2 shows the configuration of the capacitance detection circuit 13 and the x drive circuit 12, FIG. 3 shows the configuration of the capacitance detection circuit 14, and FIG. 4 shows the electric signals generated by those circuits. Show. Please refer to FIGS.

Carrier oscillator 1 of x drive circuit 12 (FIG. 2)
2d generates a high-frequency carrier, and an AM (amplitude) modulator 1
2c and 12g are driving signals SD having substantially the same frequency as the resonance frequency of the vibrating frame 6 and the x vibrator of the vibrator 8, respectively.
a, SDb amplitude modulated carrier wave and x excitation signal VD
a, VDb, and a high-frequency AC electrostatic drive voltage (amplified voltage of VDa, VDb) having the same central potential as the potential of the vibration frame 6 (common potential GND) via output amplifiers 12 e, 12 h. , To the fixed electrodes 9a and 9b.

Since the driving signals SDa and SDb are in opposite phases, the vibration frame 6 vibrates in the x direction, and the capacitances of the fixed electrodes 10a and 10b for detecting x vibration and the vibration frame 6 are in opposite phases. Vibrate. An electric signal representing this capacitance (fig.
The feedback signals VFBa and VFBb are generated by the capacitance / voltage conversion circuits 13a and 13b. Since the differential amplifier 13c differentially amplifies the x-phase vibration feedback signals VFBa and VFBb having the opposite phases, the amplified output is supplied to the low-pass filter 13d. The carrier wave is the drive signal SDa, SD
The frequency f2 is 100 times or more higher than the frequency f1 of b, and the cutoff frequency fc of the low-pass filter 13d is set as follows: fc = √ (f1 × f2) (1) ).

As a result, the feedback signal from which the high-frequency noise caused by the carrier is cut off is converted to the low-pass filter 1.
From 3d, it is given to the amplitude adjustment circuit 12a of the x drive circuit 12. The amplitude adjustment circuit 12a monitors the amplitude of the applied feedback signal and amplifies the feedback signal so that the amplitude becomes the set value Vref. The feedback signal whose level is thus standardized is supplied to the phase shifter 12b. When the vibration frame 6 (including the vibrator 8) vibrates x at its resonance frequency, the phase shifter 12b
Based on the phase delay of the drive signal SDa with respect to the feedback signal VFBa, the feedback signal VFBa is delayed by a phase delay within ± 45 degrees (°) of the reference, and this is converted into a binary wave having a duty of 50%. And the driving signal S
It is given to the AM modulator 12c as Da. Drive signal SDa
Is generated by the inverter 12f and supplied to the AM modulator 12g as a drive signal SDb.

The capacitance detection circuit 14 (FIG. 3) has the same configuration as the capacitance detection circuit 13 described above. If an angular velocity about the z-axis is applied to the vibrator 8 while the vibrator 8 is vibrating in the x direction, the x vibration of the vibrator 8 becomes an elliptical vibration along the x, y plane. That is, a y component (y vibration) corresponding to the angular velocity appears. Thereby, the fixed electrodes 11a for angular velocity detection,
The capacitance of 11b and the vibrator 8 vibrate in opposite phases. An electric signal (angular velocity detection signal) VY representing this capacitance
a / VYb are generated by capacitance / voltage conversion circuits 14a and 14b. The differential amplifier 14c detects the angular velocity detection signal V having the opposite phase.
Since Ya and VYb are differentially amplified, the amplified output is supplied to the low-pass filter 14d. Since the frequency of the y-vibration of the carrier is substantially the same as the frequency f1 of the drive signal SDa, the cutoff frequency of the low-pass filter 14d is set to be the same as that of the low-pass filter 13d.

The angular velocity detection signal VY output from the low-pass filter 14d is supplied to the signal processing circuit 15 together with the feedback signal VFB. The signal processing circuit 15 outputs the angular velocity detection signal V to the feedback signal VFB level.
Based on the level of Y, an electric signal indicating the direction of the angular velocity (forward and reverse rotation directions around the z axis) and the intensity of the angular velocity is generated.

In the above embodiment, the drive signals SDa,
SDb is a square wave, but may be another waveform such as a sine wave with a DC offset as long as it is the same frequency as the vibration frequency f1, or a sine wave having a frequency of の of the vibration frequency f1 and having no offset. It may be a triangle wave. In addition, although a rectangular wave is used as a high frequency serving as a carrier wave, a triangular wave or a sine wave may be used.

A drive voltage (carrier f)
The induced voltage of 2) is mixed as drive noise. But,
As shown in FIG. 5, since the driving noise is different in frequency from the driving signals SDa and SDb (f1) and is in a high frequency band, it can be easily separated by the low-pass filters 13d and 14d or the band-pass filters. Carrier frequency f2
Is set to 100 times or more of the vibration frequency (f1), it becomes easier to remove the driving noise, and the driving noise can be removed by a low-order filter. Filter 13d,
By setting the cutoff frequency fc of 14d to be higher than the drive frequency f1 and lower than the frequency f2 of the carrier, the phase rotation of the detection signals VFB and VY by the filters 13d and 14d can be suppressed small, and the drive noise can be reliably removed.

Further, fixed electrodes 10a, 10
b / 11a and 11b are arranged so as to detect the vibrations in opposite phases, and the differential amplifiers 13c and 14c differentially amplify the opposite detection signals to thereby in-phase the drive noise mixed in the vibration detection system. Since the components are canceled, the noise removal effect is even higher.

By setting the phase difference between the x drive signal SDa and the feedback signal VFBa of the x vibration within ± 45 deg with respect to the phase difference at the time of resonance of the vibrating body, the amplitude rate of the vibration can be increased. Since a large amplitude can be obtained with a small driving force, the driving voltage can be reduced, the power supply voltage can be reduced, and the driving noise due to the driving voltage can be reduced. Is a simple low-order filter.

By setting the center potential of the drive voltage to the same potential (GND) as the vibrator 8, the high potential (+)
The force acting on the vibration frame 6 at the time and the time of the low potential (−) becomes equal, the occurrence of unnecessary modes (vibration components other than the x vibration component) in the force acting on the vibration frame 6 is reduced, and the vibration frame 6 (vibration Child 8)
Is stabilized.

Second Embodiment FIG. 6 shows a second embodiment of the present invention. The angular velocity sensor shown here drives and oscillates in parallel (x direction) with respect to the substrate 1 and outputs an axis (y
The vibration in the vertical direction (z-direction) with respect to the substrate of the diaphragm induced by the Coriolis force generated by the application of the angular velocity about the axis of rotation is detected from the change in capacitance.

The first diaphragm 81 and the second diaphragm 82 are
The first diaphragm 81 is fixed to the fixed electrodes 9a1 and 9b so as to be able to vibrate in the x and z directions.
1, the second diaphragm 82 becomes fixed electrodes 9a2 and 9b2.
Is driven in the x direction. The x drive circuit 12 applies x excitation signals VDa to the fixed electrodes 9a1 and 9b2.
The x excitation voltage obtained by amplifying the x excitation signal VDb is applied to the fixed electrodes 9b1 and 9a2, so that the first and second diaphragms 81 and 82 vibrate x in opposite phases. . X drive circuit 12 used in second embodiment
Has the circuit configuration shown in FIG. Other configurations of the electric circuit of the second embodiment are the same as those of the first embodiment.

When an angular velocity about the y-axis is applied to the diaphragms 81 and 82, the x-vibration of the diaphragms 81 and 82 is changed into an elliptical vibration along the x-z plane, and a z-component (z-vibration) appears. The z-vibrations of the vibration plates 81 and 82 with respect to the flat plate-like fixed electrodes 11a and 11b for z-vibration detection are relatively opposite in phase, and the capacitance detection circuit 14 detects the 8/1
It generates angular velocity detection signals VYa and VYb representing the change in capacitance between 1a and 82 / 11b, generates a differentially amplified signal VY of these signals, passes it through a low-pass filter, and performs signal processing. Output to the circuit 15.

In the second embodiment, the fixed electrodes 9a1, 9a
The wiring on the substrate 1 connected to b1, 9a2 and 9b2 is covered with an insulating layer, and a conductive layer 16 for an electrostatic shield is laminated thereon except for the fixed electrode area. An insulating layer for insulating the fixed electrodes 11a and 11b is coated on the conductive layer 16, and the fixed electrodes 11a and 11b are formed on the insulating layer. Therefore, the fixed electrodes 11a having a large area,
11b has substantially the entire surface electrostatically shielded by the conductive layer 16, and is hard to pick up driving noise despite its large area.

In the second embodiment, the fixed electrodes 10a1, 10b1, 10a2, and 10b2 detect the x vibration of the vibration plates 81 and 82. The electric circuit for driving the angular velocity sensor and the electric circuit for detecting the angular velocity are, as described above, the x drive circuit 1
2 is similar to that of the first embodiment except that it has voltage output amplifiers 12e, 12h, 12i, and 12j for applying the x excitation voltage to the four fixed electrodes. The effect can be obtained similarly.

[Brief description of the drawings]

FIG. 1 is a plan view showing a sensor structure according to a first embodiment of the present invention, and an electric circuit is shown by blocks.

FIG. 2 is a block diagram showing a configuration of a capacitance detection circuit 13 and an x drive circuit 12 shown in FIG.

FIG. 3 is a block diagram showing a configuration of a capacitance detection circuit 14 shown in FIG.

FIG. 4 is a time chart showing an output signal of the electric circuit shown in FIGS. 2 and 3;

FIG. 5 shows the carrier frequency and x drive signal SD shown in FIG.
It is a graph which shows the distribution and level of the frequency of a (x vibration).

FIG. 6 is a plan view showing a sensor structure according to a second embodiment of the present invention, and an electric circuit is shown by blocks.

FIG. 7 is a block diagram showing a configuration of an x drive circuit 12 shown in FIG.

[Explanation of symbols]

1: substrate 2a to 2d: anchor 3a to 3d: support beam 4a, 4b: parallel beam 5a to 5d: support beam 6: vibrating frame 7a to 7d: support beam 8: vibrator 9a, 9b: fixed electrode for x excitation 10a, 10b: x
Fixed electrodes for detecting vibrations 11a, 11b: Fixed electrodes for detecting y vibration or z vibration due to angular velocity 13c, 14c: Differential amplifier

Claims (3)

[Claims] 1. A vibrating member floatingly supported on a substrate in a state capable of vibrating in an x direction and a direction orthogonal thereto, a driving fixed electrode for applying an electrostatic force for exciting the x direction to the vibrating member, A driving circuit for applying a voltage for driving in the x direction to the fixed electrode; and an electric signal detecting an angular velocity corresponding vibration of the vibration member in a direction orthogonal to the x direction by applying an angular velocity to the vibration member by electrostatic detection. A fixed electrode for detection and a vibration detection circuit for converting into an electrostatically driven angular velocity detection device, comprising: a carrier wave having a frequency higher than the vibration frequency in the x direction of the vibration member; An amplitude modulator for generating an x-excitation signal amplitude-modulated by the drive signal, and voltage output means for generating a voltage corresponding to the x-excitation signal and applying the voltage to the drive fixed electrode. Features,
An electrostatically driven angular velocity detector. 2. The electrostatic sensor according to claim 1, wherein said vibration detecting circuit includes a low-pass filter for extracting a low-frequency signal corresponding to the vibration frequency of an electric signal detected from the vibration corresponding to the angular velocity of the vibration member. Drive angular velocity detector. 3. The apparatus further includes an excitation detection fixed electrode for detecting x-vibration of the vibrating member, and an excitation detection circuit, wherein the excitation detection circuit detects an x-vibration of the vibration member. 2. The driving circuit according to claim 1, further comprising a low-pass filter for extracting a low-frequency signal corresponding to the vibration frequency, wherein the driving circuit shifts a phase of the low-frequency signal extracted by the excitation detecting circuit to the driving signal. 3. The electrostatically driven angular velocity detecting device according to 2.