JPH0942973A - Angle speed sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide at low-cost a small and light angle speed sensor with high sensitivity, high precision and hardly influenced with disturbance acceleration and other noise by mass-producing by a semiconductor technique. SOLUTION: An angle speed sensor comprises a base plate, a vibration mass 14 isolatedly formed on the main face of the base to vibrate toward the first and second axes crossing each other, at least two supports 16 supporting the vibration mass 14, arranged in symmetry with the first and second axes and having an equal spring constant to both axes, a driving means for a driving electrode 13 fixed to the base to drive the vibration mass 14 toward the first axis and a detecting means for a detecting electrode 15 fixed to the base to detect the displacement of the vibration mass 14 toward the second axis. The vibration mass 14 and the supports 16 are held at a common potential and the driving electrode 13 is divided to apply plural voltage values thereto, so that Coriolis force, generated toward the second axis when the vibration mass 14 being vibrated toward the first axis is rotated around the third axis perpendicular to the main face of the base, is detected to measure an angle speed around the third axis.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small, lightweight, highly mass-producible and highly accurate angular velocity sensor.

[0002]

2. Description of the Related Art As a conventional angular velocity sensor, for example,
There is a first conventional example as shown in FIG. In the figure, reference numeral 2 is a vibrator having a square cross section formed of a constant elastic metal such as enriver, and is supported by a supporting portion 3. The driving piezoelectric element 4 and the detecting piezoelectric element 1 are fixed to the side surface of the vibrator. An AC voltage having a resonance frequency in the x-axis direction is applied to the driving piezoelectric element 4, and by distorting the AC voltage, the vibrator is driven in the x-axis direction in the drawing to vibrate. In this state, z
When the oscillator is rotated around the axial direction at an angular velocity Ω, Coriolis force is generated in the y-axis direction in the figure. The Coriolis force Fc (t) generated in the entire vibrator can be expressed by the following equation (1).

Fc (t) = 2 · Ω · ∫dm (r) · Vm (r, t) (1) where Vm (r, t) is a mass dm generated by driving the vibrator. It is the velocity in the x-axis direction of the minute portion having (r). The integration range is the whole oscillator. The oscillator is bent in the y-axis direction by the generated Coriolis force, and the strain generated by this bending is detected by the detection piezoelectric element 1.
From equation (1), in order to generate a larger Coriolis force, a: increase the mass of the oscillator, b: drive at the resonance frequency and increase Vm, c: resonance of the drive axis and the detection axis. It can be seen that it is effective to match the frequencies and increase the displacement on the detection axis. To detect the generated Coriolis force with high accuracy, d: keep the vibration amplitude of the oscillator constant. is necessary. However, in the angular velocity sensor of the first conventional example as described above, a: a vibrator and a supporting portion are machined to be manufactured, and therefore there is a limit to miniaturization.
b: There was a problem that it was difficult to adjust the resonance frequency of each axis of the vibrator, and the mechanical adjustment cost increased.

In order to solve the above problems, Japanese Unexamined Patent Publication No. 5-248872 (1993) discloses FIGS. 31 and 32 (FIG. 3).
The angular velocity sensor as shown in FIG. The configuration will be described below with reference to the drawings.
In the second conventional example, the vibrator is formed on the substrate 12 made of silicon or the like. The vibrating system includes a vibrating mass 10, an intermediate support portion 11 and a support portion 8. The vibrating mass 10, the intermediate support portion 11 and the support portion 8 are formed of, for example, a polysilicon layer. The support part 8 is the anchor part 7.
Are fixed to the silicon substrate 12 by means of and are electrically connected by a conductive pattern. Further, 5 is a fixed part. The electrical wiring is not shown in order to simplify the drawing. The intermediate support 11 is supported by the support 8 in the middle of the anchor 7. The vibrating mass 10 is supported by a supporting portion 8 arranged in a cross shape in the x- and y-axis directions around the vibrating mass. A drive electrode 6 for driving the vibrating mass 10 in the x-axis direction by electrostatic attraction is provided on the side surface of the intermediate support portion 11.
Is paired. Y on the other side of the middle support
A detection electrode 9 for detecting the displacement due to the Coriolis force in the axial direction is formed.

Next, the operation of the second conventional example will be described. The vibration system applies a driving voltage V to each of the pair of driving electrodes 6.
P + vd · sin ωt and Vp−vd · sin ωt are applied and driven by electrostatic attraction. However, Vp is a DC bias power supply, and vd · sinωt is a driving AC power supply pressure. The drive frequency ω is designed to match the resonance frequency of the vibration system in the x-axis direction. In this state, when the vibrating system composed of the vibrating mass, the intermediate supporting portion and the supporting portion is rotated at the angular velocity Ω around the z-axis direction, Coriolis force is generated in the y-axis direction in the vibrating system. The generated Coriolis force is expressed by the following equation (2).

Fc (t) ≈2 · m · Vm (t) · Ω (2) where m is the mass of the oscillating mass 10 and Vm (t) is the oscillating mass oscillated by being driven by electrostatic attraction. 10 speeds. However, it was assumed that the mass of the intermediate support part was sufficiently smaller than the vibration mass. Therefore, the angular velocity Ω can be detected from the capacitance value between the detection electrodes 9.

With the above-mentioned structure, in the second conventional example, in contrast to the above-mentioned problems of the first conventional example, a: a semiconductor manufacturing technique can realize a small and inexpensive angular velocity sensor (the first conventional example). 1 against the problem a of the conventional example), b:
Since the vibration system has a planar structure formed of a polysilicon layer and the driving and detecting directions are parallel to the substrate plane, a three-dimensional structure is unnecessary and the structure can be simplified (first conventional example). C): c: Since the vibration system has a planar structure formed of a polysilicon layer and has a symmetrical shape with respect to both drive and detection directions, the resonance frequencies in both directions match and the sensitivity is improved (first In contrast to the problem b of the conventional example), d: Since the drive and detection directions are parallel to the substrate plane, the dependence of the resonant frequency in the drive axis and detection axis directions on the cross-sectional shape of the support is equal. Yes,
There is no change in the relative value of the resonance frequency in both directions due to process variations (against the problem b of the first conventional example), e: both the drive axis and the detection axis are parallel to the substrate plane,
In the vibration state, the effect of air viscosity is reduced, the Q value at the time of resonance is increased, and the detection sensitivity is improved.

However, in the second conventional example, since the vibrating mass is supported by the supporting portion which can be displaced only in one direction, a: the vibrating mass is intermediate through the pair of supporting portions extending in the y-axis direction. Since it is connected to the support part, when it is driven in the x-axis direction, it is drawn in the direction of the oscillating mass by the support part together with the intermediate support parts on both sides (see FIG. 33), and as a result, the intermediate support part 11 is more than the rest position. Each of them vibrates in the y-axis direction at a frequency double the driving frequency centering on the position offset in the oscillating mass direction, which causes a difference in the vibration mode between the detection direction and the driving direction, which is the vibration necessary for highly accurate measurement of the angular velocity. It becomes difficult to control the vibration of the mass, and if there is a difference in the left and right vibrations due to manufacturing variations of the support part, etc., a drive vibration-induced output signal is generated, and the S / N ratio of the detection signal decreases. , B: Since the motion direction and the detection direction have the same resonance frequency, there is a possibility that the detection direction component of the driving force may resonate in the detection axis direction due to the asymmetry of the structure caused by the manufacturing variation of the support portion. In the case of the example, there is a problem that the drive-induced vibration cannot be controlled, is detected as an output signal, and the measurement accuracy may decrease.

An angular velocity sensor that also utilizes semiconductor manufacturing technology is disclosed in Japanese Patent Application Laid-Open No. 315576/1993. This third conventional example is shown in FIGS. 34 and 35 (A in FIG. 34).
-A 'sectional view). In the figure, 63 and 65 are silicon substrates, and 64 is an oxide film. Silicon substrate 65
After the oxide film 64 is formed on the substrate, the oxide film 64 is patterned and bonded to the silicon substrate 63 by the direct bonding method, and then the silicon substrate 63 is polished to a predetermined thickness.
Reference numeral 59 is a groove formed by etching the silicon substrate 63 using a semiconductor manufacturing technique. The groove portion 59 forms the oscillating mass, the first and second support portions, and the frame portion which will be described below. Reference numeral 61 denotes an oscillating mass, which is supported by the first support portion 60. The side of the first support portion 60 opposite to the connection portion with the vibration mass 61 is connected to the frame portion 57 to form a connection portion. The frame portion 57 is supported by the second support portion 56. A comb-teeth electrode 62 for driving and vibrating the vibrating mass 61 in the x-axis direction by electrostatic attraction is formed in the frame portion 57. In order to detect the displacement of the oscillating mass 61 due to the Coriolis force, a resistance bridge composed of two piezoresistors 55 arranged in parallel for each support part is provided near the connection part of the first support part 60 with the frame part 57. In addition, the vibrating mass 61 and the detection electrode 58 on the frame 57
Is configured (details of electrical wiring are omitted for simplification of the drawing).

The frame portion 57 supported by the second support portion 56 is driven by electrostatic attraction in the x-axis direction by applying a voltage to the comb-teeth electrode 62 (details of electrical wiring are simplified in the drawing). Omitted for). In this state, when the whole body is rotated around the z-axis direction perpendicular to the substrate plane at an angular velocity Ω, a Coriolis force similar to that already expressed by the equation (2) is generated in the y-axis direction. The displacement of the vibrating mass 61 in the y-axis direction due to the generated Coriolis force is detected as a resistance difference of the piezoresistor 55 or a change in electric capacitance between the detection electrodes 58.

In the third conventional example, since a: semiconductor technology is used, a small and inexpensive angular velocity sensor can be realized. B: Both the drive axis and the Coriolis force detection axis are parallel to the substrate plane. The resonance frequency in the axis and detection axis directions can be determined by a planar structure. C: Since both the drive axis and the detection axis are parallel to the substrate plane, the influence of air viscosity is reduced in the vibrating state, and the Q value at resonance increases. Advantages such as improved detection sensitivity can be obtained. However, in the third conventional example, since the oscillating mass is made of semiconductor,
The mass m in the equation (2) is small, and the generated Coriolis force is very small. Therefore, it is practically impossible to measure with the resistance bridge composed of the piezoresistor 55, and the displacement of the oscillating mass is changed by the capacitance change of the detection electrode 58. Need to measure. However, since the detection electrode 58 is formed on the side surface of the vibrating mass 61 and the frame 57, the facing area is small and the capacitance value cannot be sufficiently secured. As a result, there is a problem that the S / N ratio cannot be sufficiently secured when measuring the displacement of the vibrating mass. Further, also in the comb-teeth electrode 62 for driving the vibrating mass, it is difficult to secure a sufficient facing area, and there is a problem that a sufficient drive amplitude cannot be obtained. Further, the piezoresistor 55 for detecting the displacement of the vibrating mass 61 due to the generated Coriolis force or the frame portion 57 of the vibrating mass.
Detection electrode 58 for detecting displacement with respect to
There is also a problem that it is difficult to miniaturize the supporting portion and the drive electrode because it is necessary to electrically connect the supporting portion and the driving electrode through the supporting portion and to electrically separate the above portions. Furthermore, when a metal such as Al is used for the above electrical connection, a difference in thermal expansion coefficient occurs between silicon and the insulating film, which is the structure forming the support portion, and therefore the structural stress is generated by the structural body. There is a risk that the output will be offset due to warpage, etc., and plastic deformation will occur in the metal part due to the large deformation of the support part,
There is also a problem in that the output may deteriorate over time.

[0012]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned various problems of the prior art, is compact and lightweight, can obtain accurate detection results, and is highly mass-producible. The challenge is to provide.

[0013]

In order to solve the above problems, in the present invention, a substrate and a first axial direction and a second axial direction which are formed on the main surface of the substrate and are orthogonal to each other in the main surface of the substrate are provided. An oscillating mass that vibrates in the direction of at least 2 and has one end fixed to the oscillating mass and the other end fixed to the substrate to support the oscillating mass and are symmetrically arranged in the directions of the first axis and the second axis and having a spring constant equal to both axes. One support part, a drive electrode fixed to the substrate and driving the oscillating mass in the first axis direction, and a driving means, and a detection electrode fixed to the substrate and detecting means for detecting displacement of the oscillating mass in the second axis direction and the detecting means. The vibrating mass and the supporting part are held at a common potential, the driving electrodes are divided so that voltages of multiple values can be applied, and the vibrating mass is driven in the first axis direction to vibrate while being perpendicular to the main surface of the substrate. The second axis when rotated around the third axis Around a rotational angular velocity of the third shaft has to be measured by detecting the Coriolis force generated in the direction.

Further, as described above, instead of separately disposing the drive electrode for driving in the first axis direction and the detection electrode for detecting the displacement in the second axis direction, two electrically independent electrodes are used. It is similar in that it uses a counter electrode constructed,
Driving voltages V1 and V2 are simultaneously applied to these two electrodes to drive them in the first axis direction by an electrostatic attractive force generated between the opposing electrodes, and electrostatic capacitance between the two fixed electrodes constituting the opposing electrodes and the vibrating mass side electrode. Let C1 and C2 respectively be C1
The information on the drive amplitude of the oscillating mass in the first axis direction is detected from the sum of C2 and C2, and the information on the displacement in the second axis direction due to the Coriolis force of the oscillating mass is detected from the difference between C1 and C2. The driving and the Coriolis force detection may be combined.

[0015]

Since the drive electrodes are divided so that a plurality of voltages can be independently applied, there is a problem even if the vibrating mass and the supporting portion are formed asymmetrically in the first axis direction during the manufacturing process. You can prevent it from happening.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in more detail based on the embodiments.

First Embodiment: A first embodiment will be described with reference to FIGS. 1 and 2 (cross-sectional view taken along the line BB 'in FIG. 1). The present embodiment includes claims (1), (2) and (4).
Corresponds to (15). First, the basic configuration will be described. Reference numeral 14 is an oscillating mass made of a thin film structural material. Vibration mass 14
Are also formed of thin film structural material at the four corners, and x
It is connected to the support portion 16 having the same spring constant in both the (first axis) and y (second axis) axial directions. In addition, in the figure, the supporting portion is schematically shown. The supporting portions 16 are arranged symmetrically with respect to both the x and y axes as shown in the figure. The other end of the supporting portion is fixed to the substrate at the fixing portion 17 and is electrically connected to the conductive material (the wiring is not shown for simplification of the drawing). A plurality of comb-teeth-shaped electrodes are formed on the side surface of the vibrating mass 14, and the vibrating mass 14 is driven in the x-axis direction by electrostatic attraction between the comb-teeth-shaped electrodes connected to the fixed portion 17. Drive electrode pair 13 for forming. The portion of the drive electrode pair 13 is enlarged and shown in FIG. The comb-shaped drive electrode fixed to the substrate is composed of an electrode 21 facing the right side and an electrode 20 facing the left side of the comb-shaped drive electrode on the vibrating mass side, so that a drive voltage can be applied to each independently. It has become. Further, a plurality of comb-teeth-shaped electrodes are formed on the side surface of the vibrating mass 14 (only one set is shown in the drawing), and a capacitance between the comb-teeth-shaped counter electrode connected to the fixed portion 17 is formed. The change in the value forms the detection electrode pair 15 for detecting the displacement of the vibrating mass 14 in the y-axis direction. An enlarged view of the detection electrode pair is shown in FIG. The arrangement of the comb-teeth electrodes in this case is, as shown in FIG. 6, d1 so that the opposing comb-teeth electrode pairs do not interfere with each other.
<< d2.

Next, the support portion of this embodiment will be described in detail. The supporting portion having the same spring constant in both the x and y axis directions can be displaced and deformed in the xy plane in the figure, and the x axis and the y axis can be deformed.
It can be realized by using a structure symmetrical in the axial direction that divides the angle formed by the axes into two equal parts. Some examples are shown in FIGS.
It is shown in FIG. 14 shows an example in which a symmetric structure is realized by one structural element. Since the symmetry axis is set in a direction that divides the angle formed by the x and y axes into two equal parts, the x axis and the y axis
The modes of deformation of the structure in the axial direction are equalized, and the spring constants are equal in both axial directions. FIG. 15 shows an example in which a symmetric structure is realized by a plurality of structural elements. Since the symmetry axis is set in a direction that divides the angle formed by the x and y axes into two equal parts, x
And the modes of deformation of the structure in the y-axis direction become equal, and have the same spring constant in both axial directions. Compared with the example shown in FIG. 14, the effect that the design change of the spring constant can be easily made by increasing or decreasing the structural elements is obtained.

There are a plurality of types of creation processes, which will be described below. 1. An example of the fabrication process when polysilicon is the structural material is shown in FIG. (A) After forming the high-concentration diffusion layer 22, the silicon substrate is oxidized to form the oxide film 24, and the silicon nitride film 23 is deposited on the entire surface of the oxide film 24. (B) A passivation film 27 such as PSG is deposited on the entire surface. After forming a contact hole reaching the high concentration diffusion layer, a polysilicon film 25 is deposited, impurities are diffused if necessary, and then the polysilicon film is patterned. (C) After forming a contact hole reaching the high-concentration diffusion layer, a metal wiring 26 is deposited and patterned. (D) A passivation film 27 such as PSG is deposited on the entire surface, patterned, and then a silicon nitride film 28 is deposited and patterned for protection of metal wiring and peripheral circuits. (E) A passivation film such as PSG, which is a sacrificial layer, is removed using a hydrofluoric acid-based solution to form a polysilicon structural material. Although omitted in the above description, by integrating the peripheral circuit section on the same substrate, not only fine signal processing becomes possible, but it is also advantageous for downsizing and cost reduction of the sensor.

2. An example of the manufacturing process when the SOI layer is a structural material is shown in FIG. In this manufacturing process, the first silicon substrate is oxidized and bonded to the second silicon substrate through the oxide film by the direct bonding method, and then the second silicon substrate is polished to a predetermined thickness, and the SOI substrate is used. . (A) After forming the high-concentration diffusion layer 29 in the SOI layer, it is oxidized to cover the entire surface with the oxide film 24. (B) After depositing a passivation film 30 such as PSG on the entire surface, a contact hole reaching the high concentration diffusion layer 29 is formed. After that, a metal to be a wiring is deposited on the entire surface and patterned to form a metal wiring 26. (C) After depositing the passivation film 30 such as PSG again on the entire surface, the passivation film 30 and the oxide film 24
Is performed. (D) After depositing the silicon nitride film 23 on the entire surface, patterning is performed to form a protective film for the metal wiring and the peripheral circuit portion. After that, a groove 3 is formed in the SOI layer by using a technique such as RIE.
Form one.

(E) Using the oxide film under the SOI layer as a sacrifice layer, it is removed with a hydrofluoric acid-based solution to form a vibrating mass and a supporting portion. Although omitted in the above description, by integrating the peripheral circuit section on the same substrate, not only fine signal processing becomes possible, but it is also advantageous for downsizing and cost reduction of the sensor.

3. FIG. 10 shows an example of a manufacturing process when the plated metal is a structural material. (A) First, a high concentration diffusion layer 22 is formed on a silicon substrate, and an oxide film 24 is formed on the entire surface. After that, a silicon nitride film 23 is deposited on the entire surface as a passivation film. (B) Metal film overall deposition and patterning, PSG or other passivation film overall deposition, formation of contact holes in metal film wiring, metal film overall deposition and patterning, PSG or other passivation film overall deposition and patterning, metal wiring and surroundings A silicon nitride film for protecting the circuit portion is blanket deposited and patterned. (C) Depositing and patterning the metal film 33 as a sacrifice layer by a plating method, and depositing and patterning the metal film 32 as a structural material by a plating method. (D) The sacrificial layer metal film 33 is removed using an acid-based solution,
An oscillating mass and each support part are comprised. Although omitted in the above description, by integrating the peripheral circuit portion on the same substrate, not only fine signal processing becomes possible, but also it is advantageous for downsizing and cost reduction of the sensor.

Next, the operation of this embodiment will be described. FIG. 11 shows an example of a vibrating mass drive and signal detection circuit.
Shown in By applying a predetermined drive voltage to the drive electrode ends Td1 and Td2 alternately with respect to the potential Vm of the vibrating mass 14, the vibrating mass 14 supported by the support portion 16 is driven in the x-axis direction to vibrate. Resonance frequency f of the vibrating mass in the x-axis direction
xr is determined by the mass of the oscillating mass and the spring constant in the x-axis direction of the support connected to the four corners of the oscillating mass. Therefore, the resonance state can be easily realized by electrically adjusting the applied frequency of the driving power source OSC1 of 34.

In order to measure the Coriolis force with high accuracy, it is necessary to drive the vibrating mass at a constant frequency and a constant amplitude.
Since the vibration frequency matches the drive frequency, the frequency of OSC1 may be kept constant. For the constant amplitude control, for example, the configuration shown in FIG. 11 may be used. The reference capacitance Cr2 is connected in series between the drive electrode ends Td1 and Td2 and the drive power source. The impedance of the electric capacitance is expressed by the following equation (3): Zc = 1 / jωC (3), and Cr2 is sufficiently larger than the electric capacitances Cd1 and Cd2 between each drive electrode end and the oscillating mass. For example, drive voltage Cr
The loss in 2 is almost negligible. Actual Cd1, C
Since the value of d2 is about pF, it is easy to realize Cr2 even on the same substrate. When drive voltages D and D (representing the logical NOT of D) are applied via the reference capacitance Cr2, the potentials at the drive electrode terminals Td1 and Td2 are taken out via the buffer 38 and the difference is demodulated. If the detector 37 detects it in synchronization with the driving frequency of the driving power source OSC1, information about the vibration amplitude of the vibrating mass can be obtained. Therefore, by applying negative feedback to the driving power source OSC1 so that the obtained amplitude information has a predetermined value, it is possible to drive the vibrating mass at a constant amplitude. There is a possibility that the inter-electrode gap of the drive electrodes may vary due to the variation of the residual stress generated in the supporting portion during the manufacturing process. For example, in the ideal state shown in FIG. 4A, d3 = d4. In this case, the electrostatic attractive forces in the y-axis direction cancel each other out, and the driving force generated in the vibrating mass 14 is only in the x-axis direction. However, if the state of d3 ≠ d4 occurs as shown in FIG. 4B for the reason described above, when the deviation of the gap from the ideal state is δ (d3-d4 = 2 * δ), the drive in the x-axis direction is performed. The force is the same as in the ideal state, but an electrostatic attractive force represented by the following formula (4) is generated in the y-axis direction per pair of drive electrodes.

Fy = ε ₀ · (L · t) / d ₀ ² · Vd ² · 4 · (δ / d ₀ ) ... (4) where ε ₀ : dielectric constant L: drive electrode facing length t: drive electrode Thickness d ₀ : gap between electrodes in ideal state Vd: drive voltage The electrostatic attractive force represented by the equation (4) has a resonance frequency in the drive axis direction. In the case of the structure of the present embodiment, since the resonance frequencies of the drive shaft and the resonance shaft match, there is a possibility that the electrostatic attraction may induce vibration in the direction of the detection axis and generate an unwanted signal in the output.

However, the driving force distribution can be adjusted by the method shown in FIG. 5 to eliminate the influence of the gap variation. FIG. 5A is an enlarged schematic view of the drive electrode portion,
It is shown that the drive electrode fixed to the substrate is divided into an electrode 21 facing the right side and an electrode 20 facing the left side of the vibrating mass side electrode. When a gap variation occurs, as shown in FIG. 5B, the drive voltage applied to the electrodes 20 and 21 is adjusted using the adjustment resistor Rt, and the vibration in the detection axis direction induced by the drive voltage is suppressed. be able to.

When the vibrating mass is vibrated with a constant amplitude, when it is rotated around the z axis shown in FIG. 1 at an angular velocity Ω,
Coriolis force shown by the following equation (2) is generated in the y-axis direction. Fc (t) ≈2 · m · Vm (t) · Ω (2) where m is the mass of the oscillating mass and Vm (t) is the speed of the oscillating mass in the x-axis direction. When a vibrating mass vibrates at the resonance frequency fxr by applying a trigonometric wave-like driving force, the displacement of the vibrating mass in the x-axis direction is delayed by π / 2 phase with respect to the driving force. Therefore, Vm which is the differential amount of displacement of the oscillating mass
(T) and the Coriolis force Fc in the y-axis direction proportional thereto
(T) changes at the same frequency and the same phase as the driving force. Therefore, if the resonance frequency fyr in the y-axis direction of the vibrating mass supported by the support portion matches the resonance frequency fxr in the x-axis direction which is the drive shaft, the displacement in the y-axis direction due to the Coriolis force can be increased.

In the case of the present embodiment, four vibration masses are used,
It has a structure that is displaceable and deformable in the x and y planes and that is symmetrical in the axial direction that bisects the angle formed by the x axis and the y axis, and thus has the same spring constant in both the x and y axis directions. Since it is supported by the supporting portion, the resonance frequency fyr in the y-axis direction matches the resonance frequency fxr in the x-axis direction. The spring constant may be slightly different in each of the positive and negative directions of the x and y axes in one support part. However, as in the case of the present embodiment, the support part supporting the vibrating mass is provided with respect to the x and y axes. By arranging them symmetrically, the above influence can be eliminated. Also, the vibration modes in both directions can be made the same (however, the displacement in the y-axis direction is shifted by π / 2 phase from the Coriolis force which is the driving force).

When the structure of the vibrating mass, the supporting portion and the comb-teeth electrode is constituted by a thin film having a predetermined thickness as in the present embodiment, the mass of each member is the density of the structural material and x, y.
Determined by the area in the plane. In addition, the spring constants of the support portion in the x-axis and y-axis directions are the rigidity ratio of the support member and x,
It is determined only by the shape and cross-sectional shape in the y-plane, ie the geometrical moment of inertia. Therefore, the resonant frequencies in both the x and y axis directions can be determined by the thickness of the structural material and the structural design of the x and y planes. When variations in the thickness and length of the structural material and the cross-sectional shape as shown in FIG. 7 occur due to variations in the manufacturing process, the change in the resonance frequency in each axial direction is as follows (5) in the x and y axis directions. , Z-axis direction is expressed by the following equation (6).

Δf / fx, y = − (3/4) × δ− (5/2) × (ΔL / L) (5) Δf / fz = −Δt / t− (1/4) × δ− (5/2) × (ΔL / L) (6) where δ = (b−a) / b: Change in cross-sectional shape of the supporting portion Δt / t: Deviation in thickness of structural material ΔL / L: Of structural material Therefore, as can be seen from the equation (5), if the deviation is constant within the same angular velocity sensor, the relative value does not change even if the absolute values of the resonance frequencies in the x and y axis directions change. The sensitivity can be increased only by adjusting the drive frequency of the drive power supply OSC1.

The change in the capacitance of the detection electrode pair due to the Coriolis force expressed by the equation (2) may be detected, for example, as shown in FIG. A reference capacitance substantially equal to the capacitance between each detection electrode and the oscillating mass side electrode between each detection electrode end Vs1, Vs2 and 35 detection power supply OSC2 having a frequency sufficiently higher than the driving power supply OSC1 of 34. Cr1 is connected in series. Detection voltage C via the reference capacitance Cr1
Is applied, the difference between the potentials of the detection electrode ends Vs1 and Vs2 is detected by the demodulator 37 via the buffer 38.
If the detection is performed in synchronization with the drive frequency of the detection power supply OSC2, the displacement amount in the y-axis direction due to the Coriolis force changing at the frequency of the drive power supply OSC1 of 34 can be obtained. Therefore, FIG.
As shown in FIG. 1, if the signal is processed again in synchronization with the driving frequency of the OSC1, a DC signal corresponding to the displacement amount in the y-axis direction can be obtained.

An example of another detection method is shown in FIG. As in the case of FIG. 11, when the detection voltage C is applied to each detection electrode end via the reference capacitance Cr1, the potential difference between the detection electrode ends Vs1 and Vs2 is detected by the demodulator 37 via the buffer 38. If the detection is performed in synchronization with the drive frequency of the detection power source OSC2, the displacement amount in the y-axis direction due to the Coriolis force that changes with the frequency of the drive power source OSC1 can be obtained. By inputting the signal thus obtained to the peak hold circuit 39 and detecting the maximum signal, a DC signal corresponding to the amount of displacement in the y-axis direction due to the Coriolis force is obtained.

FIG. 13 shows an example of still another detection method. As in the case of FIG. 11, the detection voltage C is applied to each of the detection electrode ends Vs1 and Vs2 via the reference capacitance Cr1. In this case, the detected voltage source OSC3 is the drive power source OSC1.
Has the same frequency as and has a phase difference δ with respect to OSC1.
Shall have. In the operating state, there is a certain phase difference between the displacement in the x-axis direction due to the driving force and the displacement in the y-axis direction due to the Coriolis force. Therefore, the OSC3 is adjusted to adjust the phase difference with the OSC1, and each detection electrode end Vs is adjusted.
The potentials of 1 and Vs2 are supplied to the demodulator 3 via the buffer 38.
7 detects in synchronization with the frequency of the detection power supply OSC3 (frequency is equal to OSC1 and differs only in phase) 40,
If the difference is taken, a DC signal corresponding to the amount of displacement in the y-axis direction due to the Coriolis force can be obtained.

The DC-like disturbance acceleration input in the x-axis direction affects the output as a change in the vibration amplitude of the vibrating mass. This effect can be eliminated by monitoring the vibration amplitude and taking the configuration shown in FIGS. 11, 12, and 13 so as to keep it constant.

The DC-like disturbance acceleration input in the z-axis direction affects the output as a change in the vibration amplitude of the vibrating mass and a change in the facing area of the detection electrode. The influence of the change in the vibration amplitude can be removed by the same method as in the x-axis direction. The influence on the output due to the change in the facing area of the detection electrodes can be eliminated by the circuit configuration as shown in FIGS. 11, 12 and 13 which detects the differential capacitance of the detection electrode pair.

For DC-like disturbance acceleration input in the y-axis direction, a pair of angular velocity sensors as in this embodiment are installed side by side,
The respective oscillating masses are driven in opposite phases, and the angular velocity sensor 1
It can be eliminated by taking the difference between the outputs of each pair, and the angular velocity can be detected with higher accuracy. Further, by taking the sum of the outputs of the angular velocity sensors, it is possible to detect a DC external acceleration input in the detection axis direction (y-axis direction).

Particularly, when exposed to an AC disturbance acceleration input in the x- and y-axis directions, vibration due to resonance is induced in the x-axis direction and the y-axis direction to affect the output, but the resonance frequency in each axis direction is affected. If it is designed sufficiently high, a low-pass filter can be configured by the mounting structure of the sensor to suppress AC-like disturbance acceleration input.

Although only the angular velocity detector is shown in the drawings for explaining the present embodiment, the drive and signal processing circuits for the entire detector as shown in FIGS. 11, 12 and 13 are formed on the same substrate. By doing so, it is possible to greatly reduce the influence of external noise mixed while inputting a minute signal generated by detecting the angular velocity to the processing circuit. Also, the reference capacitance Cr1 pair,
It is possible to improve the pairing of the electric capacity of the Cr2 pair,
The driving force and the offset of the output signal can be reduced.

The effects of the first embodiment will be described below. a: Since the vibrating mass is supported by arranging the support portions having the same spring constants in the drive axis and the detection axis directions symmetrically with respect to the directions of the two axes, the resonance frequency and the vibration mode in the two axis directions are equal to each other. Highly accurate measurement of angular velocity is possible. b: Since the drive electrode that opposes the oscillating mass and drives it by electrostatic attraction is divided and the drive voltage can be independently applied, the drive vibration can be controlled with high accuracy. c: Driving and vibrating in the plane direction and detecting in the plane direction, it is easy to design the relative resonance frequency of the drive shaft and the detection shaft. d: Since the vibrating mass having a planar structure vibrates in parallel to the substrate plane, a high Q value is obtained at resonance. e: Driving and vibrating in the plane direction and detection in the plane direction, the electrodes can be configured two-dimensionally and the structure is simplified. f: Since the angular velocity sensor is realized by using the semiconductor manufacturing technology, it is possible to reduce the size, the weight, and the cost, and it is possible to correspond to the mass production of the sensor having uniform characteristics. g: The sensor characteristics can be designed only with a two-dimensional structure. h: By using electrostatic attraction drive and electrostatic capacitance detection,
The vibrating mass and each supporting portion can have the same potential, and electrical wiring is easy. i: By using electrostatic attraction drive and electrostatic capacitance detection,
Since the oscillating mass and each support can be set to the same potential, electrical wiring by metal, polysilicon, or high-concentration diffusion layer on each support is not required, and output due to difference in thermal expansion coefficient of each structural member The adverse effect of can be eliminated. j: By using electrostatic attraction drive and electrostatic capacitance detection,
Since the vibrating mass and each support can be set to the same potential, electrical wiring by metal, polysilicon, or high-concentration diffusion layer on each support is unnecessary, and when metal wiring is used on each support The offset or hysteresis that may occur due to the plastic deformation of the metal wiring can be eliminated. k: Since the vibrating mass is directly driven, the vibration amplitude of the vibrating mass can be controlled with higher accuracy. l: Since the vibrating mass and the supporting portion are formed by the surface type microstructure, the resonance frequency of the mechanical system can be designed to be high. Therefore, if the low-pass filter for the AC-like disturbance acceleration input is configured by the mounting structure of the sensor, it is possible to eliminate the adverse effect on the output due to the AC-like disturbance acceleration input. m: Constant control of vibration amplitude is possible without using electrodes for monitoring vibration amplitude. n: By the constant control of the vibration amplitude by driving and the detection of the differential capacitance of the detection capacitance, it is possible to remove the adverse effect on the output of the DC-based disturbance acceleration input to the drive axis and the angular velocity input axis of the vibration amplitude. o: By using a pair of angular velocity sensors that drive the oscillating mass in opposite phases, and by taking the difference between the outputs, it is possible to eliminate the adverse effect of the DC-like disturbance acceleration input in the detection axis direction on the output, and to achieve higher accuracy. It is possible to detect angular velocity. p: A pair of angular velocity sensors that drive the oscillating mass in opposite phases are used, and the acceleration in the detection axis direction can be detected by taking the sum of the respective outputs. q: If the detection unit, the drive circuit of the detection unit, and the signal processing circuit are formed on the same substrate, the influence of external noise mixed while inputting a minute generated signal to the processing circuit can be significantly reduced. Also, the pairing of the reference capacitances Cr1 and Cr2 can be improved, and the driving force and the offset of the output signal can be reduced. By adding an r: AC servo mechanism and using the feedback amount as an output signal, higher sensitivity can be achieved. Second Embodiment: A second embodiment of the present invention will be described with reference to FIG. The present embodiment corresponds to claims 1, 3 to 15. The basic configuration is as shown in FIG. 3, where x,
A plurality of elastic structures that have the same spring constants in both y-axis directions and can be displaced and deformed in the x- and y-planes are symmetrically supported in the axial direction that bisects the angle between the x-axis and the y-axis. It can be realized by arranging as 18. Two examples are shown in FIG. In addition, each of the plurality of elastic structures is illustrated in FIGS.
5 may be used. In these figures, 14 is an oscillating mass, 17 is a fixed part, and 18 is a support part. x-axis,
Since the axis of symmetry is set in a direction that bisects the angle formed by the y-axis, the modes of deformation of the structure in the x-axis direction and the y-axis direction are equal, and the spring constants are equal in both axial directions.

The manufacturing process for producing is the same as in the case of the first embodiment. Further, although it operates in the same manner as in the first embodiment, in the case of the second embodiment, the oscillating mass can be displaced and deformed in the xy plane, and the same spring constant can be obtained in both the x and y axial directions. Since the plurality of elastic structures that are provided are respectively supported by the support portions that are symmetrically arranged in a direction that bisects the angle formed by the x-axis direction and the y-axis direction, the resonance frequency fyr in the y-axis direction is x. Axial resonance frequency fxr
Matches There may be cases where the spring constants of the one support part are slightly different in the positive and negative directions of the x and y axes, but as in the present embodiment, the support part that supports the oscillating mass is different from the x and y axes. By arranging them symmetrically, the above influence can be eliminated. Further, the vibration modes in both directions can be made the same (however, the displacement in the y-axis direction is out of phase by π / 2 from the Coriolis force which is the driving force). The same effects as those of the first embodiment can be obtained in the second embodiment.

Third Embodiment: In the third embodiment, unlike the above-described first and second embodiments, only one type of electrode is arranged on the side of the vibrating mass. There is no distinction between x-axis driving and y-axis displacement detection by Coriolis force. However, in order to deal with the difference in the gap between the electrodes, the fixed electrode is divided into two groups to which different potentials can be applied, as in the first and second embodiments.

Regarding the third embodiment, first, the state of the comb-teeth electrode pair composed of the vibrating mass side electrode and the fixed side electrode will be described with reference to FIGS. 17 and 18. These figures are schematic plan views of the oscillating mass of the angular velocity sensor formed of the thin film structural material and the facing (fixed) electrode portion. In the figure, reference numeral 66 denotes an oscillating mass, which is supported (not shown for simplification of the drawing) by a supporting portion described later. The oscillating mass is also connected to the common potential via the support. 70 is a comb-tooth electrode extending from the side surface of the vibrating mass. In the comb-teeth electrode 70, the counter electrodes face each other with a predetermined gap between the electrodes. In FIG. 17, counter electrodes 68 and 69 are opposed to both side surfaces of one comb-tooth electrode 70, respectively. In FIG. 18, the counter electrode 68 or 69 faces one side surface of one comb-tooth electrode 70 to form a pair. The counter electrodes 68 and 69 are connected to the extraction electrode 71 at the connection portion 67 and are connected to the peripheral circuit (the peripheral circuit is not shown for simplification of the drawing). The counter electrodes 68 and 69 are electrically independent, and each constitutes a capacitance between the oscillating masses. The oscillating mass and the counter electrode as shown in the drawing can be made by using a known technique using crystalline silicon or polycrystalline silicon. Generally, the thickness of the vibrating mass and the counter electrode is about several μm.

FIGS. 19 and 20 are schematic plan views of the method for supporting the oscillating mass (these figures show the counter electrode structure shown in FIG. 17, but the counter electrode shown in FIG. 18 also realizes the same. it can). In FIG. 19, 72 is an oscillating mass formed of a thin film structural material. The vibrating mass 72 is also formed of a thin film structural material at the four corners, and is connected to a support portion 73 having the same spring constant in both the x and y axis directions (the support portion is shown schematically). The support portions are arranged symmetrically with respect to both x and y axes. The other end of the supporting portion is fixed to the substrate at the fixing portion 74 and is electrically connected to the conductive material (the wiring is not shown for simplification of the drawing). The oscillating mass is a support portion 73 having a spring constant equal to both x and y axes.
Since it is supported by, it can be displaced in both the x and y axis directions and has the same resonance frequency. A portion 75 surrounded by a broken line is an electrode portion. In FIG. 20, the support portion 76 is a direction in which a plurality of elastic structures that are displaceable in the x and y planes are divided into two equal parts in the x-axis and y-axis directions, respectively. Are arranged symmetrically. Since the axis of symmetry is set in a direction that bisects the angle formed by the x and y axes, the support portion 76 has the same spring constant in both axial directions. The supported oscillating mass 72 is displaceable in the x-axis and y-axis directions,
And have the same resonance frequency.

Next, the structure of the detection circuit will be described with reference to FIG. In this figure, the capacitances between the counter electrode terminals R1, R2, L1, L2 and the oscillating mass shown in FIGS. 19 and 20 are CR1, CR2, CL1, CL2, respectively. A portion 77 surrounded by a broken line represents the vibration mass, and CR
The node to which 1, CR2, CL1 and CL2 are connected represents the potential of the oscillating mass, which is connected to the common potential via the support. Counter electrode terminals R1, R2, L1, L2
Are substantially equal DC bias values VR1 and VR, respectively.
2, VL1 and VL2. Further, reference electric capacitances Cref79 are connected to the counter electrode terminals R1, R2, L1, L2, respectively, and CR1, CR2, CL
1 and CL2 are driven by a drive voltage V via a reference capacitance Cref.
1, V2, V1 and V2 are applied. In addition, 7
Reference numeral 8 is a detected capacitance. Therefore, the counter electrode terminals R1, R
DC bias value VR is applied to each of 2, L1 and L2.
1, VR2, VL1, VL2 and the sum of the driving voltages V1, V2, V1 —, V2 — via the reference capacitance Cref are applied. The voltages of the counter electrode terminals R1, R2, L1 and L2 are input to the buffer 80 and subjected to impedance conversion, and then signal processing is performed. Although omitted in FIG. 21 for simplification of the drawing, actually, as shown in FIG. 25, resistors are connected in parallel to the reference capacitor and CR1, CR2, CL1, CL2 to stabilize the DC bias value of the output voltage. (Fig. 25 schematically shows one of the four capacities).

The voltages of R1 and R2 and the voltages of L1 and L2 are added by the adder 81, then the difference is obtained by the subtractor 82, and the difference is input to the demodulator 83 via the high pass filter 89. After detecting the synchronization with the oscillator 86 by the demodulator 83,
After passing through the low-pass filter 84, a part is fed back to the oscillator 85 for self-oscillation of the oscillating mass, and another part is input again to the demodulator 83. This time, after performing synchronous detection with the oscillator 85, the low-pass filter It is input to the control circuit 87 via 84 as amplitude information of the oscillating mass. The control circuit 87 outputs an output proportional to the angular velocity and a voltage signal synchronized with the oscillator 85. The voltage signal synchronized with the oscillator 85 is
After a part of the signal is input to the inverter 88, a part of the signal is input as it is to the adder 81.
6 output, and those outputs are added to the reference capacitance Cre.
Applied to f to drive the oscillating mass. L1 and R1 and L2
And the voltage of R2 are added by the adder 81, and then the subtractor 8
The difference is obtained by 2, and this is input to the demodulator 83 via the high-pass filter 89, this time synchronous detection is performed with the oscillator 86, and then the control circuit 87 as the displacement information by the Coriolis force of the oscillating mass via the low-pass filter 84. To enter.

The control circuit 87 is realized, for example, as shown in FIG. The displacement information and the amplitude information are input to the calculator 91, respectively. The calculator 91 calculates the modulation amount of the drive voltage according to the deviation from the zero level as the displacement information and the deviation from the set reference level as the amplitude information. In the figure, the modulation amount is indicated by a for displacement information and b for amplitude information. The modulation amount a is output as the angular velocity input via the amplifier 93. Further, a part of the modulation amount a remains as it is, and the other part has its sign inverted by the inverter 88, and then added with the modulation amount b by the adder 81 to obtain the modulation amount Δ of the driving voltage.
₁ and Δ ₂ are calculated. That is, Δ ₁ = a + b (7) Δ ₂ = −a + b (8) The calculated modulation amounts Δ ₁ and Δ ₂ are input to the amplitude modulator 92, which modulates the amplitude of the oscillator 85 according to the amplitudes and outputs drive voltages Vd1 and Vd2.

Returning to FIG. 21, the synchronization detection by the oscillator 86 in the demodulator 83 is performed by the homodyne method in which the frequency of the signal is detected by using the PLL element 89 as shown in FIG. You may go. Further, the signals synchronously detected by the oscillator 85 in the demodulator 83 are input to the control circuit 87 as amplitude information and displacement information, respectively, but the demodulator may be replaced with an integrating circuit.

Next, the operation of the above circuit for driving the oscillating mass will be described. Counter electrode R via reference capacitance Cref
When a voltage V is applied to 1, R2, L1 and L2, an electrostatic attractive force Fd as shown in the following formula (9) is applied in the drive axis direction of the oscillating mass.
Occurs.

Fd = −n / 2 · ε ₀ · t / d ₀ · V ² (9) However, n: the number of electrodes facing the comb-teeth electrode of the oscillating mass ε ₀ ; permittivity t; comb-teeth electrode Thickness d ₀ ; represents the electrode interval, and the negative sign indicates that the driving force is generated so that the overlapping of the electrodes increases. Since the impedance of the electric capacitance is expressed as the above-mentioned formula (3) Z _C = 1 / jωC (3), the driving voltage of AC is applied to the oscillating mass via the reference capacitance Cref as shown in FIG. Is applied, the capacitance between the vibrating mass and the counter electrodes CR1, CL1,
The AC drive voltage applied to CR2 and CL2 is (1)
It is expressed as in equation (0).

V _˜ = 1 / (C _S / Cref + 1) × V _˜drive (10) where V _˜ ; electric capacity CR1, between the oscillating mass and the counter electrode
CL1, CR2, AC driving voltage CL2 is applied to the _V ~drive; driving voltage is applied via the capacitance Cref V
1, V2, V1 ￣, V2 ￣ C _S ; capacitance between the vibrating mass and the counter electrode CR1, CL
1, CR2, CL2 Therefore, Cref is the capacitance between the vibrating mass and the counter electrode CR
If it is made sufficiently larger than 1, CL1, CR2, CL2, the loss in the drive voltage Cref can be almost ignored. Further, by driving and vibrating, the electric capacitances CR1, CL1,
Even if CR2 and CL2 change, the applied AC drive voltage is the drive voltage V1, V2, V1 via the electric capacitance Cref.
Proportional to ￣, V2 ￣. Actual CR1, CL1, CR
Since the values of 2 and CL2 are about pF, it is easy to realize Cref even on the same substrate. As the drive voltage, as shown in FIG. 24, an oscillator 85 having a period that matches the resonance frequency of the oscillating mass, and an oscillator 86 (OSC2, which has a frequency sufficiently higher than the oscillator 85 (OSC1, amplitude; vd) and a small output amplitude). The sum of the outputs of s amplitude; vc) is used. More specifically, in FIG. 21, the oscillator 85 (O
The output of SC1) is input to the control circuit 87, and the adder 81 generates the sum of the output of the control circuit 87 and the output of the oscillator 86 (OSC2). Drive voltage V generated
1 and V2 are connected to R1 and R2 in FIGS. 19 and 20 via the reference capacitance Cref, and V1 and V2 are reference capacitance Cref.
Is applied to L1 and L2 in FIG. 19 and FIG. For V1, V2 and V1 and V2, oscillator 85 (OS
The output of C1) is in antiphase. R1, R2 and L1, L
The voltage in equation (9) applied to 2 is
The sum of the AC voltages V1, V2, V1 and V2 applied via the C bias and the reference capacitance Cref, that is, (11),
It becomes as shown in Expression (12).

V ₁ , V 2 = V _bias + vd · sin ω ₁ t + vc · sin ω ₂ t (11) V ₁ −, V 2 − = V _bias −vd · sin ω ₁ t + vc · sin ω ₂ t (12) However, V _bias ; DC bias voltage of counter electrode terminals R1, R2, L1, L2 ω ₁ ; oscillation frequency of oscillator 85 (OSC1) vd; output amplitude of oscillator 85 (OSC1) ω ₂ ; oscillation frequency of oscillator 86 (OSC2) vc; oscillator 86 Output amplitude of (OSC2) The electrostatic attractive force obtained by substituting the equations (11) and (12) into the equation (9) is the opposite direction between R1 and R2 and L1 and L2.
Eventually, an electrostatic driving force represented by the following formula (13) is generated in the vibrating mass.

F _drive ∝V _bias · vd · sin ω ₁ t + vd · vc · sin ω ₁ t · sin ω ₂ t (13) The second term can be ignored if vd >> vc. Furthermore ω ₁
Since it has a sufficiently higher frequency, it does not affect the vibration system having a resonance frequency near ω ₁ . Therefore, the oscillating mass is ω
_Vibrates at ₁ .

Assuming that the capacitance between the counter electrode terminals R1, R2, L1 and L2 and the vibrating mass is C _S , the comb-teeth electrode overlap at rest is L, and the comb-teeth electrode interval is d, the x-axis of the vibrating mass is shown. The change in C _S due to the direction drive and the y-axis displacement due to the Coriolis force is expressed by the following equation (14).

C _S = Cs ⁰ (1 + x / L) / (1 + y / d) (14) Where, Cs ⁰ : Capacitance at rest Output vd of oscillator 85 (OSC 1) and oscillator via reference capacitance AC voltage V _to R1, V _to R of counter electrode terminals R1, R2, L1 and L2 when the sum of the output vc of 86 (OSC2) is applied to the counter electrode as shown in the detection circuit of FIG.
2, V _to L1 and V _to L1 are as shown in the following equations (15) to (18) by substituting the equation (14) into the equation (10). However, only the first-order terms of x / L and y / d were developed.

V _to R1 = 1 / B · (1-A · x / L + A · y / d) · (vd + vc) (15) V _to R2 = 1 / B · (1-A · x / LA) -Y / d)-(vd + vc) ... (16) V _- L1 = 1 / B- (1 + A-x / L + A-y / d)-(-vd + vc) _- (17) V _- L2 = 1 / B- ( 1 + A · x / L- A · y / d) · (-vd + vc) ... (18) ^{where, A = (Cs 0 / Cr} ) / ((Cs 0 / Cr) +1) B = (Cs 0 / Cr) +1 Cr: Reference capacitance Displacement x due to driving of the oscillating mass is obtained as follows. V
The voltages of R1 and VR2 and VL1 and VL2 are stored in the buffer 80.
After impedance conversion is performed in step S1, the adder 81 adds the values, and the subtracter 82 determines the difference. The result is (1
It is shown like a formula (9).

(VR1 + VR2) − (VL1 + VL2) = 4 / B · (vd−A · x / L · vc) (19) The first term is input to the demodulator 83 after being removed via the high-pass filter 89. . After the demodulator 83 detects synchronization with the oscillator 86, the low-pass filter 84 smoothes the signal.
The smoothed signal has the same frequency as the oscillator 85 (OSC1), and the amplitude is a signal proportional to the driving amplitude of the oscillating mass. This signal is an oscillator 85 (OSC
Return to 1). At the same time, in order to realize the AGC function, the demodulator 83 again detects the synchronization with the oscillator 85, smoothes it with the low-pass filter 84, and then drives the drive voltages V1 and V2.
Input to the control circuit 87 that controls the amplitude of the.

The displacement y of the oscillating mass due to the Coriolis force is determined as follows. The Coriolis force generated is as described in (2) above.
Since it is proportional to the vibration velocity of the vibrating mass as shown in the equation, in the case of the third embodiment, the amplitude is a signal proportional to the displacement due to the Coriolis force at the same frequency as the oscillator 85 (OSC1).

After impedance conversion of the voltages of VR1 and VL1 and VR2 and VL2 by the buffer 80, the adder 8
1 is added and the subtractor 82 calculates the difference. The result is shown by the following equation (20). (VR1 + VL1) − (VR2 + VL2) = 4A / B · y / d · vc (20) This is input to the demodulator 83 via the high-pass filter 89. After detecting the synchronization with the oscillator 86 by the demodulator 83,
Smoothing is performed by the low pass filter 84. The smoothed signal has the same frequency as the oscillator 85 (OSC1), and the amplitude becomes a signal proportional to the displacement due to the Coriolis force. The signal is input again to the demodulator 83, this time the synchronization with the oscillator 85 is detected, and then smoothing is performed by the low-pass filter 84. The smoothed signal becomes a signal proportional to the displacement of the oscillating mass due to the Coriolis force, and the control circuit 8 for modulating the drive voltages V1 and V2.
7 is input. In the synchronization detection by the oscillator 86 in the demodulator 83, as shown in FIG.
High-accuracy demodulation is possible by detecting the frequency of the signal by using and performing homodyne detection that performs synchronous detection at that frequency.

Drive voltages V1 and V2 in the control circuit 87
Is modulated as follows. By applying a drive voltage via the reference capacitance Cref, between the vibrating mass and the counter electrode,
In the direction of the Coriolis force detection axis in FIGS.
An electrostatic attractive force as shown by the equations (1) and (22) is generated. That direction is the direction in which the gap between the electrodes is narrowed.

Fs ¹ = ε ₀ m · Lt / (d ₀ ) ² · (CV ₁ ) ² (21) Fs ² = ε ₀ m · Lt / (d ₀ ) ² · (CV ₂ ) ² …… (22) where m is the number of pairs of counter electrodes C is a coefficient representing the driving voltage drop due to the reference capacitance Cref, ε _{0 is the} dielectric constant L, the length of the electrodes facing each other t is the thickness of the electrodes, and the driving voltage is V ₁ = V ⁰ _1. (1 + Δ ₁ ), V ₂ = V ⁰ ₂ (1+
In order to cancel the generated Coriolis force Fc by modulating with Δ ₂ ), the relationship of the following equation (23) should be satisfied.

Fc = F ¹ _S −F ² _S ≈ε ₀ m · (CV ⁰ ) ² / d ² · (Δ ₁ −Δ ₂ ) ... (23) However, for simplicity, V ⁰ = V ⁰ ₁ = It was the V ⁰ _2. The driving force applied to the oscillating mass at this time can be similarly expressed by the following equation (24). Fd≈ε ₀ mt · (CV ⁰ ) ² / d · {1+ (Δ ₁ + Δ ₂ )} (24) Therefore, the drive voltage is modulated as shown in the equations (7) and (8), and the inverse By applying the modulation ± a having the same sign and the same absolute value, it is possible to compensate the generated Coriolis force without affecting the drive amplitude of the vibrating mass as in the following formula (25).

Fc≈ε ₀ m · (CV ⁰ ) ² / d ² · 2a (25) When the driving amplitude of the oscillating mass changes due to disturbance input, etc., (7), (8) By modulating the drive voltage as shown in the equation and applying the modulation b having the same absolute value and the same sign, the electrostatic mass in the detection axis direction is not generated in the vibrating mass as in the following equation (26). , The driving force can be changed and the amplitude can be controlled.

Fd≈ε ₀ mt · (CV ⁰ ) ² / d · {1 + 2b} (26) In the control circuit 87, the amplitude information of the oscillating mass and the displacement information due to the Coriolis force are input at the same time. The drive voltage modulation can be performed to realize uniform drive amplitude and compensation of Coriolis force at the same time, and the angular velocity sensor with a simple structure enables highly accurate detection.

The following effects can be obtained in the third embodiment. a: Since the detection electrode and the drive electrode are shared and the driving of the oscillating mass and the measurement of the displacement due to the Coriolis force can be performed at the same time, the potential and capacitance of the electrode facing the oscillating mass can be efficiently secured. b: Since the electrodes facing the vibrating mass are divided into two and voltage can be independently applied to each of them, the drive amplitude of the vibrating mass can be made constant and the Coriolis force generated can be compensated at the same time. c: The measurement range of angular velocity is expanded because the Coriolis force is compensated by the drive voltage. d: Since the Coriolis force is compensated by the drive voltage, the vibrating mass does not vibrate in the detection axis direction. Therefore, more accurate angular velocity measurement is possible.

Fourth Embodiment: This embodiment relates to claim 19. The configuration of the angular velocity sensor is the same as that of the third embodiment. The configuration of the detection circuit of this embodiment is shown in FIG. Only parts that are different from the third embodiment (FIG. 21) will be described. In the present embodiment, after detection in synchronization with the oscillator 86 (OSC2) in the demodulator 83, the signals whose waveforms have been shaped through the low pass filter are input to the control circuit 87 as displacement information and amplitude information, respectively. The outputs Vd1 and Vd2 from the control circuit are partially unchanged, and the other part is passed through the inverter 88 to the ideal diode circuit 90.
To enter. The oscillator 8 is provided at the output of the ideal diode circuit 90.
6 (OSC2) outputs are added to drive voltages V1, V2,
V1 and V2 are applied to the oscillating mass through the reference capacitor 79.

FIG. 28 shows the drive voltages V1, V2, V1 and V2 applied via the reference capacitor 79. The driving voltage is composed of a voltage vd for generating a driving force and a voltage vc for reading displacement by Coriolis force, which has a sufficiently smaller amplitude than the amplitude of the oscillating mass and vd.
vd is an output through the inverter 88 of the oscillator 85 (OSC1) and the ideal diode circuit 90. vc is the output of the oscillator 86 (OSC2). vc is shown in FIG.
28B or a bipolar pulse as shown in FIG. 28B. vd and vc are applied alternately. In the figure, a time zone in which no voltage is applied is provided between vd and vc application, but the essential functions are the same even if this time zone is not provided. vd is V1, V2 and V
It is applied in opposite phase at 1 and V2. vc is V1, V2 and V1 ￣, V2 ￣ in the time period τ when vd is not applied.
Are applied simultaneously. The oscillating mass is generated by the oscillator 85 by the electrostatic attractive force generated by the application of vd according to the above-mentioned equation (9).
It is excited at the same frequency as (OSC1). The read voltage vc is applied to V1, V2 and V1 ￣, V2 ￣ at the same time, so if the vibrating mass is not displaced by the Coriolis force, vc
The electrostatic attractive forces generated by the two cancel each other out. Further, since vc has a sufficiently smaller amplitude than vd, the electrostatic attractive force generated even when the vibrating mass is displaced can be ignored.

As shown in FIG. 22, the sum and the difference of the voltages of the counter electrode terminals R1, R2, L1 and L2 are obtained via the buffer 80. Furthermore, this signal is sent to the oscillator 86 (OSC
By synchronous detection with 2), information on the amplitude due to the driving of the oscillating mass and the displacement due to the Coriolis force can be obtained as in the case of the third embodiment. Subsequent processing is the same as that of the third embodiment, and will be omitted.

The fourth embodiment has the following effects in addition to the effects of the third embodiment. a: Since the displacement information and the amplitude information are obtained only by the synchronous detection by the oscillator 86 (OSC2), the signal processing circuit can be simplified. Fifth Embodiment: This embodiment particularly relates to claim 20. The configuration of the angular velocity sensor is the same as that of the third embodiment. The detection circuit configuration of this embodiment is shown in FIG.
Only parts different from the fourth embodiment (FIG. 22) will be described. In the fifth embodiment, the potential Vm of the oscillating mass is
It is connected to the oscillator 86 (OSC2). Outputs Vd1 and Vd2 from the control circuit are partially output as they are and the other is output through the inverter 88, and drive voltages V1 and Vd are output.
2, V1 and V2 are applied to the oscillating mass via the reference capacitor 79.

The drive voltages V1, V2, V1 and V2 applied through the reference capacitor 79 are shown in FIG. The driving voltage is composed of the voltage vd for generating the driving force. v
d is the oscillator 85 (OSC1)
Output). vd is V1, V2 and V1 ￣, V
Time period τ in which the phase is opposite by 2 and vd is not applied.
To be present. vc is the output of the oscillator 86 (OSC2) whose amplitude is sufficiently smaller than vd,
Applied to the oscillating mass within time zone τ. vc is FIG.
Even with a unipolar pulse as shown in FIG.
It may be a bipolar pulse as shown in (b). The oscillating mass is oscillated at the same frequency as the oscillator 85 (OSC1) by the electrostatic attractive force generated by the application of vd according to the equation (9). The read voltage vc is applied to the oscillating mass within the time period τ. If the vibrating mass is not displaced by the Coriolis force, the electrostatic attractive forces generated by vc cancel each other out. Since vc has a sufficiently smaller amplitude than vd, the electrostatic attractive force generated even when the vibrating mass is displaced can be ignored.

As shown in FIG. 27, the sum and difference of the voltages of the counter electrode terminals R1, R2, L1 and L2 are obtained via the buffer 80. Furthermore, from these signals, the oscillator 86
By the synchronization detection with (OSC2), the amplitude due to the driving of the oscillating mass and the displacement information due to the Coriolis force can be obtained as in the case of the third embodiment. Subsequent processing is the same as in the case of the third embodiment, so description will be omitted. The effect of the fifth embodiment is equivalent to the effect of the fourth embodiment.

[0071]

As described above, according to the present invention, since it is manufactured by using the semiconductor technology, it is highly sensitive, highly accurate, is not easily affected by noise such as disturbance acceleration, and is small in size.
The effect that the lightweight angular velocity sensor can be easily mass-produced at low cost can be obtained. Note that the effects have already been described in detail for each embodiment.

[Brief description of drawings]

FIG. 1 is a schematic plan view of a first embodiment.

FIG. 2 is a schematic side sectional view of the first embodiment.

FIG. 3 is a schematic plan view of a second embodiment.

FIG. 4 is a diagram for explaining an influence on a driving force of a non-uniform gap of a counter electrode formed between an oscillating mass and a fixed portion, and a means for reducing the influence.

FIG. 5 shows that the electrodes on the fixed portion are divided into two sets to which a voltage can be independently applied in order to reduce the influence on the driving force due to the gap between the counter electrodes formed between the vibrating mass and the fixed portion. It is a figure explaining.

FIG. 6 is an enlarged plan view of a detection electrode pair for detecting y-axis direction displacement due to Coriolis force.

FIG. 7 is a diagram showing an example of deviation caused in the cross-sectional shape of the structural material according to the embodiment due to variations in the manufacturing process.

FIG. 8 is a diagram illustrating a manufacturing process when polysilicon is a structural material.

FIG. 9 is a diagram illustrating a manufacturing process when the SOI layer is a structural material.

FIG. 10 is a diagram illustrating a manufacturing process when a plated metal is a structural material.

FIG. 11 is a diagram showing an example of a vibrating mass drive and signal detection circuit in the first embodiment.

FIG. 12 is a diagram showing an example of a vibrating mass drive and signal detection circuit in the first embodiment.

FIG. 13 is a diagram showing an example of a vibrating mass drive and signal detection circuit in the first embodiment.

FIG. 14 is a diagram showing an example in which a single structural element realizes an axially symmetric support portion that bisects the angle formed by the x-axis and the y-axis in the first embodiment.

FIG. 15 is a diagram showing an example in which a plurality of structural elements realize a support portion having a structure that is symmetrical in the axial direction and divides the angle between the x-axis and the y-axis into two equal parts in the first embodiment.

FIG. 16 is a diagram showing an example in which a plurality of elastic structures are symmetrically arranged in an axial direction that bisects an angle formed by an x axis and ay axis in the second embodiment.

FIG. 17 is a plan view illustrating a state of a comb-teeth electrode pair including an oscillating mass side electrode and a fixed side electrode in the third embodiment.

FIG. 18 is a plan view illustrating a state of a further simple comb-teeth electrode pair including an oscillating mass side electrode and a fixed side electrode in the third embodiment.

FIG. 19 is a schematic plan view for explaining a method of supporting an oscillating mass using a simple supporting member according to the third embodiment.

FIG. 20 is a schematic plan view for explaining a vibrating mass supporting method using a plurality of elastic structures in the third embodiment.

FIG. 21 is a diagram illustrating a configuration of an angular velocity detection circuit according to a third embodiment.

FIG. 22 is a diagram illustrating a configuration of an angular velocity detection circuit according to a fourth embodiment.

FIG. 23 is a diagram showing an example of a circuit in the case where a homodyne system in which a frequency of a signal is detected by using a PLL element in the angular velocity detection circuit and synchronization detection is performed at the frequency is used.

FIG. 24 illustrates the driving voltage applied between the opposing electrodes by the oscillator having the period equal to the resonance frequency of the oscillating mass and the oscillator having a sufficiently higher frequency and a smaller amplitude in the third embodiment. FIG.

FIG. 25 In the third embodiment, resistors are connected in parallel to the reference capacitor and the electrostatic capacitance between the counter electrode terminal and the oscillating mass to stabilize the DC bias value of the output voltage. It is a figure explaining a detection electrode circuit.

FIG. 26 is a diagram showing a configuration example of a control circuit used in the angular velocity detection circuit shown in FIG. 21.

FIG. 27 is a diagram illustrating a configuration of an angular velocity detection circuit according to a fifth embodiment.

FIG. 28 is a diagram illustrating a drive voltage applied between opposing electrodes via a reference capacitor in the fourth embodiment.

FIG. 29 is a diagram illustrating a drive voltage applied between opposing electrodes via a reference capacitor in the fifth embodiment.

FIG. 30 is a perspective view of a first conventional example of an angular velocity sensor.

FIG. 31 is a plan view of a second conventional example of the angular velocity sensor.

FIG. 32 is a side sectional view of a second conventional example of the angular velocity sensor.

FIG. 33 is a diagram for explaining that a problem occurs in the second conventional example.

FIG. 34 is a plan view of a third conventional example of the angular velocity sensor.

FIG. 35 is a side sectional view of a third conventional example of the angular velocity sensor.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Piezoelectric element for detection 2 ... Oscillator 3 ... Support part 4 ... Piezoelectric element for drive 5 ... Fixed part 6 ... Drive electrode 7 ... Anchor part 8 ... Support part 9 ... Detection electrode 10 ... Oscillating mass 11 ... Intermediate support part 12 ... Silicon substrate 13 ... Driving electrode pair 14 ... Oscillating mass 15 ... Detection electrode pair 16 ... Supporting portion 17 ... Fixing portion 18 ... Supporting portion 19 ... Driving electrode 20 ... Driving electrode fixed to the substrate facing the left side of the vibrating mass side electrode 21 ... Drive electrode fixed to the substrate facing the right side of the oscillating mass side electrode 22 ... High concentration diffusion layer 23 ... Silicon nitride film 24 ... Oxide film 25 ... Polysilicon film 26 ... Metal wiring 27 ... Passivation film 28 ... Silicon nitride film 29 ... High concentration diffusion layer 30 ... Passivation film 31 ... Groove 32 ... Plating metal film 33 ... Sacrificial layer metal film 34 ... Driving power supply OSC1 35 ... Detection power supply OSC2 36 ... Amplification 37 ... Demodulator 38 ... Buffer 39 ... Peak hold circuit 40 ... Detection voltage source OSC3 66 ... Oscillating mass 67 ... Connection part 68 ... Counter electrode 69 ... Counter electrode 70 ... Comb-shaped electrode 71 ... Extraction electrode 72 ... Oscillating mass 73 ... Support Part 74 ... Fixed part 75 ... Electrode part 76 ... Support part 77 ... Vibrating mass 78 ... Detected capacitance 79 ... Reference capacitance Cref 80 ... Buffer 81 ... Adder 82 ... Subtractor 83 ... Demodulator 84 ... Low-pass filter 85 ... Oscillator OSC1 86 ... Oscillator O
SC2 87 ... Control circuit 88 ... Inverter 89 ... High pass filter 90 ... Ideal diode circuit 91 ... Arithmetic unit 92 ... Amplitude modulator 93 ... Amplifier

Claims (20)

[Claims] 1. A substrate, an oscillating mass which is formed separately on the main surface of the substrate and oscillates in directions of a first axis and a second axis which are orthogonal to each other in the main surface of the substrate; At least two supporting portions fixed to the substrate to support the oscillating mass and symmetrically arranged in the directions of the first axis and the second axis and having equal spring constants in the directions of both axes; A drive electrode and a driving unit that are driven in the axial direction, and a detection electrode that is fixed to the substrate and that detects displacement of the vibrating mass in the second axial direction and a detecting unit, hold the vibrating mass and the supporting unit at a common potential, The drive electrode is divided so as to apply a plurality of values of voltage, and when the oscillating mass is driven around the third axis perpendicular to the main surface of the substrate while vibrating by driving in the first axis direction, the second axis By detecting the Coriolis force generated in the direction, the angle around the third axis An angular velocity sensor being characterized in that so as to measure degrees. 2. The support portion is displaceable and deformable within the main surface of the substrate,
A structure having a symmetrical structure with respect to an axis that bisects an angle formed by the first axis and the second axis in the main surface of the substrate, and has equal spring constants in the directions of the first axis and the second axis. The angular velocity sensor according to Item 1. 3. The support portion is configured such that a plurality of elastic structures that can be displaced and deformed in the main surface of the substrate are symmetrical with respect to an axis that bisects an angle between the first axis and the second axis in the main surface of the substrate. 3. The angular velocity sensor according to claim 2, wherein the angular velocity sensor is arranged in the first axial direction and the second axial direction and has the same spring constant in the first and second axial directions. 4. The driving electrode is a pair of electrodes arranged so as to face a side surface of the vibrating mass and generate a driving force in the positive and negative directions of the first axis. The angular velocity sensor according to claim 1, wherein the angular velocity sensor is a terminal of two electric capacitances connected to the common potential of. 5. The Coriolis force detecting electrodes are a pair of electrodes arranged so as to face the side surface of the oscillating mass and to detect the displacement of the second axis in the positive and negative directions. The angular velocity sensor according to claim 1, wherein the angular velocity sensor is two terminals of electric capacity connected to a common potential of the section. 6. The angular velocity sensor according to claim 4, further comprising means for detecting an amplitude of vibration of the vibrating mass in a driven state and controlling the amplitude of the vibration to be constant. 7. A reference capacitance is connected to each of the detection electrode ends, a read signal is input to the detection electrode via the reference capacitance, and the displacement of the oscillating mass in the second axis direction from the signal generated at each of the detection electrode ends. The angular velocity sensor according to claim 5, wherein 8. A reference electric capacity is connected to each drive electrode end of the oscillating mass in the first axis direction, a drive voltage is input to the drive electrode via the reference electric capacity, and driven by a voltage generated at each detection electrode end. 7. The angular velocity sensor according to claim 6, wherein the amplitude is detected, the drive voltage is controlled by the voltage generated in the detection electrode, and the drive amplitude is controlled to be constant. 9. The angular velocity sensor as claimed in claim 1, wherein the vibrating mass and the supporting portion are made of deposited polysilicon, and the substrate is made of a semiconductor substrate. 10. The angular velocity sensor according to claim 9, wherein the vibrating mass driving means and the vibrating mass displacement detecting means are integrated on the same semiconductor substrate. 11. The angular velocity sensor according to claim 1, wherein the vibrating mass, the supporting portion and the substrate are made of a semiconductor substrate. 12. The angular velocity sensor according to claim 1, wherein the vibrating mass and the supporting portion are made of metal deposited by a plating method, and the substrate is made of a semiconductor substrate. 13. The angular velocity sensor according to claim 11, wherein the vibrating mass driving means and the vibrating mass displacement detecting means are integrated on the same semiconductor substrate. 14. A pair of angular velocity sensors according to claim 1, wherein the respective oscillating masses are driven in opposite phases in the first axis direction, and the difference between the detected outputs in the second axis direction causes the oscillating mass to rotate around the third axis. An angular velocity sensor characterized by measuring an angular velocity and measuring an acceleration in the second axis direction by a sum of detected second axis direction outputs. 15. The angular velocity sensor according to claim 1, wherein
The drive electrode is a counter electrode composed of at least four electrodes that are electrically independent of each other, and the drive voltages V1 and V2 are applied to at least two electrodes of these four electrodes at the same time to generate electrostatic charges between the counter electrodes. When the electrostatic capacities between the vibrating mass and at least two of the electrodes forming the counter electrode are driven by the attractive force to be C1 and C2, respectively, the sum of C1 and C2 gives the first vibrating mass. An angular velocity sensor, which detects information about an axial drive amplitude and information about a displacement in a second axial direction due to a Coriolis force of an oscillating mass from a difference between C1 and C2. 16. Capacitance between at least two electrodes constituting the counter electrode and the oscillating mass is C1, respectively.
As C2, information on the displacement of the vibrating mass in the second axis direction due to the Coriolis force is detected from the difference between C1 and C2, and at least two of the electrodes forming the counter electrode with respect to the potential of the vibrating mass are detected from the obtained information. The angular velocity sensor according to claim 15, further comprising a control mechanism that adjusts the amplitudes of the driving voltages V1 and V2 that are simultaneously applied to the electrodes to cancel the Coriolis force generated in the vibrating mass. 17. A capacitance between at least two electrodes constituting an opposing electrode and an oscillating mass is C1, respectively.
As C2, information on the drive amplitude of the oscillating mass in the first axis direction is detected from the sum of C1 and C2, and at least two of the electrodes forming the counter electrode with respect to the potential of the oscillating mass are detected from the obtained information. Drive voltages V1 and V applied simultaneously
16. A control mechanism is provided which adjusts the amplitudes of 2 respectively to make the drive amplitude of the oscillating mass constant.
Or the angular velocity sensor described in 16. 18. The drive voltage for the oscillating mass is a sum signal of a voltage that temporally fluctuates at the first frequency and a voltage that temporally fluctuates at a second frequency higher than the first frequency, and At least two of the electrodes constituting the reference electric capacitance Cref are connected to each other, a drive voltage is applied to the counter electrode via the reference capacitance Cref, and at least two of the electrodes forming the reference electric capacitance Cref and the counter electrode are applied. The potential of each connection point with two electrodes is
The electrostatic capacitances C1 and C2 between at least two electrodes constituting the counter electrode and the oscillating mass are measured by performing the detection in synchronization with the frequency and the first frequency. 17. The angular velocity sensor according to any one of 17. 19. A driving voltage for an oscillating mass, which is a voltage that temporally fluctuates at a first frequency and has a first time zone in which no voltage is applied, and further applies a carrier voltage in the first time zone, Reference electric capacitance Cref is connected to at least two electrodes of the electrodes forming the counter electrode, and a drive voltage is applied to the counter electrode via the reference electric capacitance Cref. Capacitances C1 and C2 between at least two of the electrodes forming the counter electrode and the oscillating mass are detected by detecting the potentials of the respective connection points with at least two of them in synchronization with the carrier voltage. The angular velocity sensor according to any one of claims 15 to 17, characterized in that: 20. The driving voltage for the oscillating mass is a voltage that varies with time at a first frequency and has a first time zone in which no voltage is applied, and at least two of the electrodes forming the counter electrode are provided. A reference electric capacity Cref is connected to each electrode, a drive voltage is applied to the counter electrode via the reference electric capacity Cref, and a carrier voltage is applied to the oscillating mass in the first time zone to form the reference electric capacity Cref and the counter electrode. By detecting the potential of each connection point with at least two of the electrodes to be synchronized with the carrier voltage,
The angular velocity sensor according to any one of claims 15 to 17, wherein capacitances C1 and C2 between at least two electrodes constituting the counter electrode and the oscillating mass are measured.