JPH1089968A - Angular velocity sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an angular velocity sensor in which a driving displacement is large and whose detecting sensitivity of the Coriolis force with reference to a rotating angular velocity is high. SOLUTION: A sensor is provided with an outside vibrating frame body 4 which is supported in the hollow part 1a of a substrate 1 via one pair of outside support beams 3a, 3b arranged so as to be faced and with an inside vibrating body 6 which is arranged at the inside 4e of the outside vibrating frame body 4 via one pair of inside support beams 5a, 5b arranged so as to be faced. The outside support beams 3a, 3b and the inside support beams 5a, '5b are composed of a multilayer electrode structure in which respective layer electrodes are divided into two parts on both sides of a vertical plane passing their beam axes so as to be arranged at the inside as well as on the surface and the rear of a piezoelectric body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an angular velocity sensor that is mounted on a moving object or the like and detects the rotational angular velocity.

[0002]

2. Description of the Related Art FIG. 21 shows a conventional angular velocity sensor of this type described in Japanese Patent Application Laid-Open No. 60-213814. Reference numeral 31 denotes a substrate made of silicon. A concave portion 31a is formed in the center of the substrate, and a silicon oxide film 32 is formed in a frame shape on the upper end surface excluding the concave portion 31a. Opposite frame sides 32 a, 3 of this frame type oxide film 32
2b, a pair of outer support beams 33a, 3
3b extends toward the center of the recess 31a.

[0003] The outer frame body 34 has frame sides 34a, 34b, 3
It is formed in a square frame having 4c and 34d. The distal ends of the outer support beams 33a and 33b are connected to the center of the outer edge of one of the opposed frame sides 34a and 34b of the outer vibration frame 34, respectively. A pair of inner supporting beams 35a, 35b extend from the center of the inner edge of another opposed frame side 34c, 34d of the outer vibrating frame 34 toward the center of the concave portion 31a. Respectively.

The pair of outer support beams 33a, 33
b, outer vibration frame 34, pair of inner support beams 35a, 35
The b and the inner vibrator 36 are formed of a silicon oxide film, and are supported by the concave portion 31 a of the substrate 31 so as to be able to vibrate freely. Further, the pair of outer support beams 33a, 33b and the pair of inner support beams 35a, 35b are arranged to be orthogonal to each other, and torsionally vibrate around the central axis of those beams.

[0005] On the frame sides 34c and 34d of the outer vibration frame 34, elongated drive electrodes 37a and 37b are formed, respectively. Further, the inner supporting beams 35a, 3
On the sides 36a and 36b in the same direction as 5b, elongated detection electrodes 38a and 38b are formed, respectively. Furthermore,
On the inner vibrating body 36, a pair of inner supporting beams 35a, 35
A prismatic weight 39 that gives a load mass is formed on the line connecting b.

The drive electrodes 37a and 37b and the silicon substrate 31 on which the drive electrodes 37a and 37b face each other.
A capacitor having a silicon oxide film of the inner vibrating body 36 and air as a dielectric is formed between the bottom surface of the concave portion 31a. Similarly, the detection electrodes 38a and 38b and the silicon substrate 31 on which the detection electrodes 38a and 38b face each other.
A capacitor having a silicon oxide film of the inner vibrating body 36 and air as a dielectric is also formed between the bottom of the concave portion 31a.

The conventional angular velocity sensor 30 has the above-described structure, and its operation will be described next. Between the drive electrode 37a and the silicon substrate 31 and the drive electrode 3
Voltages having different potentials, for example, voltages of 0 V and 10 V are alternately applied between 7b and the silicon substrate 31. Then, the driving electrodes 37a and the driving electrodes 37b are alternately attracted to the bottom surface side of the concave portion 31 by electrostatic force, and the outer vibrating frame 34 (the inner vibrating body 36) is brought into a pair of outer supporting beams 33.
Vibrates like a seesaw around a and 33b. At this time, torsional vibration occurs in the pair of outer support beams 33a and 33b.

As described above, when the outer vibrating frame 34 (the inner vibrating body 36) is vibrating, the angular velocity sensor 30 rotates at the angular velocity ω about the vertical axis Z located at the center of the inner vibrating body 36. Then, the inner vibrating body 36 is caused by Coriolis force.
Starts vibrating like a seesaw around the pair of inner support beams 35a and 35b, and the detection electrodes 38a and 38b alternately approach the bottom side of the concave portion 31b. Recess 31
a detection electrode 38a or detection electrode 38 approaching the bottom surface of a
From b, a large change in capacitance can be obtained. Since the change in the capacitance is proportional to the rotational angular velocity ω of the angular velocity sensor 30, the change in the capacitance is converted into a voltage or a current to detect the rotational angular velocity, and the rotational angular velocity is integrated to integrate the angular velocity sensor 30. You can know the rotation angle of the inertial body equipped with.

[0009]

However, in the conventional angular velocity sensor, the torsional vibration of the pair of outer support beams 33a and 33b is used for driving, and the detection of the pair of inner support beams 35a and 35b is used for detection. Utilizes torsional vibration. In particular, in the detection, the detection electrode 38 is located near the axis connecting the pair of inner support beams 35a and 35b.
Since the capacitance change is small when the detection electrodes 38a and 38b are provided, the detection electrodes 38 are provided on the sides 36a and 36b as far as possible from this axis.
Although a and 38b need to be provided, the detection sensitivity could not be increased due to the dimensional restrictions of the inner vibrating body 36.
In order to increase the detection sensitivity of the Coriolis force, the distance between the drive electrodes 37a, 37b and the bottom surface of the recess 31a is increased in order to increase the displacement of the torsional vibration of the pair of outer support beams 33a, 33b. Drive electrode 37
detection electrode 38 formed on the same plane as a and 37b
a, 38b and the distance between the bottom surface of the concave portion 31a are also increased,
The change in capacitance due to the Coriolis force was small, and the detection sensitivity was low.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an angular velocity sensor having a large drive displacement and high Coriolis force detection sensitivity with respect to a rotational angular velocity.

[0011]

The present invention is characterized by the following means for achieving the above object. According to the first aspect of the present invention, an outer vibrating frame body supported via a pair of outer supporting beams disposed facing each other in a hollow portion of a substrate, and an inner side of the outer vibrating frame body facing the outer vibrating frame body. An inner vibrator supported via a pair of disposed inner support beams, wherein the outer support beam and the inner support beam are such that each layer electrode is inside and on the front and back surfaces of those piezoelectric films, and It has a multilayer electrode structure divided and arranged on both sides of a vertical plane passing through the center axis of the beam.

According to the present invention, in the outer support beam for driving, a plurality of vibration regions formed in the opposing layer electrodes are formed in a cross section orthogonal to the beam axis, and are polarized in the same direction in the vertical direction. The direction of the driving electric field of the vibration region located at the diagonal of the cross section of the outer support beam is made the same to make the expansion and contraction the same, and the driving electric field of the vibration region arranged at one diagonal and another diagonal is set. The direction and expansion and contraction are reversed. Thereby, the outer support beam for driving performs torsional vibration,
The seesaw motion (vibration) is caused in the outer vibrating frame (inner vibrator).

On the other hand, since the inner support beam for detection also has the same structure as the outer support beam, when torsional vibration based on Coriolis force is applied to the inner support beam from the inner vibrator,
An electric field in the same direction is generated in a vibration region located at a diagonal of the cross section, and the electric fields of the vibration regions arranged at one diagonal and another diagonal are reversed. Is
A positive-phase voltage and a negative-phase voltage will be generated. The angular velocity can be detected by differentially amplifying the positive and negative phase voltages.

In the above description, for convenience, the outer support beam is used for driving and the inner support beam is used for detection. However, the reverse is also possible.

According to a second aspect of the present invention, there is provided a vibrating body supported in a hollow portion of a substrate via a pair of support beams disposed opposite to each other, and each of the support beams includes a piezoelectric element having a piezoelectric layer. It consists of a multi-layer electrode structure that is divided and arranged on both sides of a vertical plane passing through the central axis of the beams inside and on the front and back of the body membrane, and one support beam vibrates in the horizontal or vertical direction The other support beams are used for detecting vertical or horizontal vibration.

According to the present invention, a pair of support beams are used for driving and detecting. The driving support beam applies an electric field in the opposite direction to the upper or lower vibration region on the left side of the vertical plane passing through the beam axis and the upper or lower vibration region on the right side. Then, the support beam vibrates the vibrating body in the horizontal direction. As described above, when the vibrating body is vibrating in the horizontal direction and the acceleration sensor of the present invention rotates about the pair of support beams, Coriolis force acts on the vibrating body, and the vibrating body moves in the vertical direction. It starts to vibrate. Then, in the support beam for detection, an electric field in the opposite direction is generated in the upper vibration region and the lower vibration region, and a voltage of the same polarity is extracted from the upper electrode and the lower electrode, and a voltage of the opposite polarity is extracted from the middle electrode. This can be differentially amplified to detect the angular velocity. According to a third aspect of the present invention, an oxide film is formed between the front and back surfaces of the support beam, the middle layer electrode, the outer vibration frame, the inner vibrator, and the vibrator.

According to the present invention, warpage is prevented by using the oxide film as a reinforcing material. In addition, the oxide film is made of a material Q
Therefore, the displacement of the bending vibration is increased by forming an oxide film in the middle layer of the vibrating body. Furthermore, since the oxide film has a frequency characteristic opposite to that of zinc oxide with respect to temperature,
Changes in the mechanical resonance frequency due to temperature changes are offset.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an angular velocity sensor 10 according to a first embodiment of the present invention will be described with reference to FIG. Reference numeral 1 denotes a substrate made of silicon, and a hollow portion 1a
And is formed in a frame shape. A silicon oxide film is provided on the frame type substrate 1, zinc oxide (ZnO) is provided thereon, and a silicon oxide film is further provided thereon to form a frame 2.

A pair of outer support beams 3a and 3b are formed from the center of the inner edge of the opposite frame sides 2a and 2b of the frame 2 to the hollow portion 1a.
The outer vibrating frame 4 is connected to the center of the outer edge of one of the opposing frame sides 4a and 4b. Another opposite frame side 4 of the outer vibration frame 4
c, a pair of inner support beams 5a, 5d from the center of the inner edge of 4d
b extends toward the center of the through hole 1a and is connected to the center of the opposing outer edge of the inner vibrating body 6 having a rectangular plate shape. The pair of inner support beams 5 a and 5 b and the inner vibrating body 6 are formed in the inner side (through hole) 4 e of the outer vibrating frame 4.

The pair of outer support beams 3a and 3b and the pair of inner support beams 5a and 5b are arranged so as to be orthogonal to each other, and each of them performs torsional vibration.

The mechanical resonance frequency of the outer vibrating frame 4 that performs torsional vibration about the pair of outer support beams 3a and 3b and the inner vibration that performs torsional vibration about the pair of inner support beams 5a and 5b. The mechanical resonance frequency of the body 6 is set so as to match or approximate. This setting is performed as follows. That is, the width of the outer support beams a and 3b and the inner support beams 5a and 5b is increased to increase the mechanical resonance frequency, or the width is reduced to decrease the mechanical resonance frequency. Further, the mechanical resonance frequency is increased by increasing the thickness of the outer support beams a and 3b and the inner support beams 5a and 5b, or the mechanical resonance frequency is decreased by decreasing the thickness. Further, the mechanical resonance frequency is lowered by increasing the mass of the inner vibrating body 6, and the mechanical resonance frequency is increased by reducing the mass.

As described above, when the mechanical resonance frequencies of the outer vibrating frame 4 and the inner vibrating body 6 match or approximate, the maximum values of their mechanical Q also match or approximate.
The displacement of the inner vibrating body 6 also increases, and the output of detection increases.

An outer vibration frame 4, a pair of outer support beams 3a,
3b, inner vibrating body 6 and a pair of inner supporting beams 5a, 5b
Is formed integrally with a piezoelectric material such as zinc oxide (ZnO) or lead zirconate titanate (PZT) using a thin film technique or a thick film multilayer technique.

Next, the structures of the outer support beams 3a and 3b and the inner support beams 5a and 5b will be described. Since these have the same structure, the outer support beam 3a is used as a representative example, Separate from the vibration frame 4,
FIG. 2 is a perspective view and FIG. 3 is a sectional view.

The outer support beam 3a has a three-layer electrode structure.
Each of these layer electrodes is divided and arranged on both sides in plane symmetry with respect to a vertical plane B passing through the center axis j of the beam of the outer support beam 3a, and upper electrodes d1, d2, middle electrodes d3, d4, and lower electrodes d.
5, d6. The outer support beam 3a is a piezoelectric film made of, for example, zinc oxide (ZnO), and has middle electrodes d3 and d4.
Are embedded in the piezoelectric film, and the upper electrodes d1, d2 and the lower electrodes d5, d6 are formed on the upper surface and the lower surface of the piezoelectric film, respectively.

The upper electrodes d1, d2 and the middle electrode d
Vibration regions r1 and r2 are respectively formed by 3 and d4. Further, the middle-layer electrodes d3 and d4 and the lower-layer electrodes d5 and d6
Thereby, the vibration regions r3 and r4 are respectively formed.

As shown by solid arrows in FIG. 3, these vibrating regions r1 to r4 are in the same direction as the lower electrodes d5 and d6 to the middle electrodes d3 and d4 and from the middle electrodes d3 and d4 to the upper electrodes d1 and d2. (Vertical direction).

Although not shown, a wiring pattern leading to the outside is formed on each of the layer electrodes d1 to d6.

Next, the operation of the angular velocity sensor 10 of this embodiment will be described. In this embodiment, as shown in FIG. 1, a pair of outer support beams 3a and 3b are used for driving, and a pair of inner support beams 5a and 5b are used for detection. In the driving outer support beam 3a, an AC voltage of 1 to 10 kHz is applied to the upper layer electrode d2, the middle layer electrode d3, and the lower layer electrode d6, as indicated by the dashed arrows in FIG. Also,
Simultaneously with the application, a voltage of the same frequency having a phase difference of 180 ° with respect to the AC voltage is applied to the upper electrode d1 and the middle electrode
4. Apply to lower electrode d5.

Then, the direction of polarization and the direction of the driving electric field of the outer support beam 3a become the same, and the vibration regions r1 and r4 extend,
The vibrating regions r2 and r3 in the opposite directions shrink and perform torsional vibration as indicated by the dashed line arrow. When the phase of the drive voltage is advanced by 180 ° and becomes opposite to the direction of the dashed arrow, the outer support beam 3a becomes
It causes torsional vibration.

On the other hand, another outer support beam 3b for driving
Since an AC voltage having a phase opposite to that of the phase applied to the outer support beam 3a is applied to each of the layer electrodes d1 to d6,
In FIG. 3, the outer support beam 3a performs torsional vibration as indicated by a dashed line, and the outer support beam 3b performs torsional vibration as indicated by a two-dot chain line. In FIG. 1, since the pair of outer support beams 3a and 3b are disposed to face each other, the pair of outer support beams 3a and 3b performs torsional vibration in the same direction about the beam axis (Y axis). This torsional vibration causes the outer vibration frame 4 (the inner vibration body 6) to perform a seesaw motion (vibration).

As described above, when the outer vibration frame 4 (inner vibrator 6) of the angular velocity sensor 10 is performing a seesaw motion (vibration), the angular velocity sensor 10 is centered on the Z axis perpendicular to the substrate surface. Assuming that the inner vibrator 6 is rotated at an angular velocity ω as indicated by an arrow, the inner vibrator 6 receives Coriolis force and performs a seesaw motion (vibration) about the X axis passing through the beam axes of the pair of inner support beams 5a and 5b. Become like This vibration is transmitted to the pair of inner support beams 5a and 5b, and the pair of inner support beams 5a and 5b performs torsional vibration as shown in FIG. Then, the pair of inner support beams 5a and 5b generate tensile stress in the vibration regions r1 and r4 located at diagonal positions in the half cycle of the torsional vibration indicated by the alternate long and short dash line, and vibrate regions r2 located at the other diagonal position. , R3, a compressive stress is generated, and a positive (+) voltage is applied to the electrodes d2, d3, and d6, and a negative (-) voltage is applied to the electrodes d1, d4, and d5.
Occur. In the next half cycle of the torsional vibration, the tensile and compressive stresses are reversed and the resulting polarity voltage is reversed. The voltage of the positive polarity and the voltage of the negative polarity are differentially amplified, and the angular velocity ω of the angular velocity sensor 10 is detected, and this is integrated to determine the rotation angle about the Z axis.

Next, an angular velocity sensor 20 according to a second embodiment of the present invention will be described with reference to FIG. Reference numeral 11 denotes a substrate having a rectangular hollow portion (through hole) 11a at the center.
It is formed in a frame shape. On this frame type substrate 11,
A silicon oxide film is provided, on which zinc oxide (Zn
O) A film is provided, and a silicon oxide film is further provided thereon to form the frame 12.

The opposite frame sides 12a, 12b of the frame 12
A pair of support beams 13a and 13b extend from the center of the inner edge of the hollow body 11a toward the center of the hollow portion 11a.
4 are respectively connected to the center portions of the opposed outer edges.

The cross section of the pair of support beams 13a and 13b is shown in FIG. 5, but has the same structure as that of the first embodiment shown in FIG. The explanation is cited.

The driving support beam 13a oscillates horizontally and the detection support beam 13b oscillates vertically. The following adjustments are made in order to increase or decrease the detection sensitivity by equalizing or approximating the mechanical resonance frequencies of the horizontal vibration and the vertical vibration. That is, the mechanical resonance frequency is increased by increasing the width of the driving support beam 13a, or the mechanical resonance frequency is decreased by decreasing the width. The mechanical resonance frequency is increased by increasing the thickness of the detection support beam 13b, or is decreased by decreasing the thickness. Further, the mechanical resonance frequency is lowered by increasing the mass of the vibrating body 14, or the mechanical resonance frequency is increased by reducing the mass. In the above embodiment, the driving support beam 13a is caused to vibrate horizontally and the detection support beam 13b is caused to vibrate in the vertical direction. However, the opposite vibration may be applied.

Next, the operation of the angular velocity sensor 20 according to the second embodiment will be described. In FIG. 5, the driving support beam 1 is shown.
An AC voltage of 1 to 10 kHz is applied to the upper electrode d2 and the lower electrode d6 on the left side of the vertical plane B of 3a. at the same time,
Upper electrode d1 and lower electrode d5 on the right side of vertical plane B
Also, a voltage 180 ° out of phase with the AC voltage is applied. Although no voltage is applied to the middle-layer electrodes d3 and d4, they may be connected to the ground. In this embodiment, the middle-layer electrodes d3 and d4 of the driving support beam 13a are unnecessary, but are left as they are shared with the detection support beam 13b.

Then, in a half cycle of the AC voltage,
The upper electrodes d1 and d2 and the lower electrodes d5 and d6 have the polarities shown in FIG. 5, and drive electric fields are generated in the vibrating regions r1 and r3 as indicated by broken arrows in the same direction as the polarization direction.
2. Assume that a driving electric field is generated at r4, as indicated by a broken arrow in the direction opposite to the polarization direction. Then, the vibration regions r1 and r3 in which the polarization direction and the driving electric field are in the same direction expand, and the vibration regions r2 and r4 in which the polarization direction and the driving electric field are in the opposite directions contract. As a result, as shown in FIG. 6, the driving support beam 13a whose base is fixed to the frame 12 is
4 will be displaced to the right. When the driving AC voltage reaches the next half cycle, the respective layer electrodes d1, d2, d5, d
6 is reversed, the expansion and contraction of the vibration regions r1 to r4 are also reversed, and the driving support beam 13a displaces the vibration body 14 to the left as shown by the solid line in FIG. In this way, the vibrating body 14 vibrates in the X-axis direction, as indicated by the dashed arrow in FIG.

As described above, the vibrating body 14 is driven by the AC voltage.
Is supposed to rotate, the angular velocity sensor 20 rotates at an angular velocity ω about the Y axis of the substrate 11. Then, the Coriolis force acts, and the vibrating body 14 vibrates in the direction perpendicular to the Z axis as indicated by the solid arrow. The vibration of the vibrating body 14 is transmitted to the detecting support beam 13b to which the vibrating body 14 is coupled, and as shown in FIG. 7, the tip of the detecting support beam 13b is fixed like a cantilever structure fixed at one end. The part is flexibly vibrated up and down. When bending vibration in the direction of the solid arrow (upward) acts on the support beam 13b for detection, the support beam 13b for detection
8, a compressive stress is generated in the upper vibration regions r1 and r2, and a tensile stress is generated in the lower vibration regions r3 and r4. An electric field is also generated as indicated by a broken arrow, and a positive (+) voltage is applied to the upper electrodes d1 and d2 and the lower electrodes d5 and d6, and a negative (−) voltage is applied to the middle electrodes d3 and d4.
Voltage is generated.

On the contrary, when the bending vibration in the direction of the dashed arrow (downward direction) acts on the support beam 13b for detection, the generated stress and the polarity of the voltage are reversed.

As described above, the voltage generated with the polarity opposite to the positive polarity is differentially amplified, the angular velocity ω of the angular velocity sensor 20 is detected, and this is integrated to determine the rotation angle about the Y axis. .

(Manufacturing Method 1) Next, the manufacturing method of the present invention will be described. The manufacturing method of the first embodiment is the same as that of the second embodiment. The method will be described with reference to FIGS.

Referring to FIG. 9, an oxide film s1 of 0.5 to 1 μm is formed on the surface of silicon substrate 11 by wet oxidation. Then, the supporting beam 13 is formed by sputtering or depositing a metal such as aluminum or gold / chromium.
a, 13b (see FIGS. 4 and 5) lower-layer electrodes d5 and d6 are formed.

Next, referring to FIG.
The zinc oxide (ZnO) and the lead zirconium titanate (P
A lower piezoelectric film z1 such as ZT) is formed to a thickness of 1 to 10 μm by sputtering.

Next, in FIG. 11, in order to form a hollow portion 12a, a portion of the piezoelectric film z1 corresponding to the hollow portion 12a is wet-etched with an acid such as hydrochloric acid or nitric acid using a resist as a mask, or It is removed by dry etching by RIE (reactive ion etching). The support beams 13a, 13a are formed by the remaining piezoelectric film z1.
The vibration regions r3 and r4 (see FIG. 5) of b are formed, and the lower layer film of the frame 12 (see FIG. 4) and the vibrator 14 are formed.

Next, referring to FIG. 12, using the resist as a mask, the middle-layer electrodes d3 and d4 are made of aluminum, gold / gold.
A metal such as chromium is formed by sputtering, vapor deposition, or the like.

Next, referring to FIG.
An upper piezoelectric film z2 such as zinc oxide (ZnO) or lead zirconate titanate (PZT) is formed to a thickness of 1 to 10 μm on the piezoelectric film z1 and the middle electrodes d3 and d4 by sputtering. . And hollow part 1
The piezoelectric film z2 of 2a is wet-etched with an acid such as hydrochloric acid or nitric acid using a resist as a mask, or RIE.
(Reactive ion etching) to remove by dry etching. The support beam 13 is formed by the remaining piezoelectric film z2.
Vibration regions r1 and r2 (see FIG. 5) of a and 13b are formed, and an upper layer film of the frame 12 (see FIG. 4) and the vibrator 14 is formed.

Next, in FIG. 14, the upper electrode d1,
d2 is formed by the same method as in the steps of FIGS.

Next, in FIG. 15, an oxide film s2 is formed to a thickness of about 1 μm on the piezoelectric film z2 formed on the substrate 11 and the upper electrodes d1 and d2 by sputtering and CVD (chemical growth method). Thereafter, the oxide films s2 and s1 in the hollow portion 12a are removed by etching using the resist as a mask. Note that the oxide film s1 may be removed in an initial step.

Next, as shown in FIG. 16, a central portion of the substrate 11 is formed on the back surface of the substrate 11 by a frame-shaped oxide film s3.
Is used as a mask and wet-etched with an etchant such as TMAH (tetra-methyl-ammonium-hydroxide),
Under the vibrating body 12 and the supporting beams 13a and 13b, a space 11a where these can freely vibrate is formed.
3 is removed by etching to complete the angular velocity sensor 20.

The outer support beams 13a (13) shown in FIG.
b) The middle-layer electrodes d3 and d4 are divided into middle-layer electrodes d3 and d3 'and middle-layer electrodes d4 and d4', respectively, as shown in FIG. An oxide film s4 such as a silicon oxide film or a silicon nitride film may be formed between the middle-layer electrodes d4 and d4 '. Similarly, in FIGS. 1 and 4, an oxide film s4 may be formed between the piezoelectric films z1 and z2 of the outer vibration frame 4, the inner vibration body 6, and the vibration body 14. As a result, the outer vibrating frame 4, the inner vibrating body 6, the vibrating body 14, and the support beams 3a, 3a
b, 5a, 5b, 13a, 13b are reinforced to prevent warpage. Also, since the silicon oxide film has a higher mechanical Q than the zinc oxide film, the displacement of the bending vibration is greater when the silicon oxide film is formed thicker in the middle layer than in the upper or lower layer of the vibrator. Further, since the silicon oxide film has a frequency characteristic opposite to that of the zinc oxide film with respect to temperature, a change in mechanical resonance frequency due to a temperature change is offset.

(Manufacturing Method 2) Next, another method of manufacturing the angular velocity sensor of the present invention will be described with reference to FIGS. In FIG. 18, the split electrodes d7 and d8 of the support beams 13a and 13b are formed by sputtering, vapor deposition, or the like using a metal such as aluminum or gold / chrome at a position where the front surface and the rear surface of the PZT substrate 21 face each other. In addition, PZT
Split electrodes d7 (d8) and d7 (d8) on both surfaces of substrate 21
Polarization is applied to each space.

In FIG. 19, the central portion of the PZT substrate 21 is subjected to laser or wet etching to
2 and support beams 23a and 23b for supporting the vibrating body 22 from both sides. The portion removed by etching becomes the hollow portion 21a. The substrate 21 thus processed
As shown in FIG. 20, two electrodes d7 and d7 and electrodes d8 and d8 are overlapped and bonded with an insulating adhesive to form an angular velocity sensor including an upper electrode d7a, a middle electrode d7b, and a lower electrode d7c. Complete. Support beam 23a
Are for driving, and the support beam 23b is for detection. In addition,
Middle layer electrode d7 which is bonded with insulating adhesive and has no conduction
The electrodes d7 and d8 of b are connected to each other by a wiring pattern outside.

In each of the above embodiments, the support beam has a three-layer electrode structure, but may have a multi-layer electrode structure.

[0055]

According to the first aspect of the present invention, a multi-layer torsionally vibrating support beam in which each layer electrode is divided on both sides of a vertical plane passing through the beam axis is used for driving and detection, and these driving electrodes are used for driving. Since the mechanical resonance frequencies of the support beam and the detection support beam are matched, the drive displacement is large and the detection sensitivity of the Coriolis force with respect to the rotational angular velocity is increased. In addition, since driving and detection are performed using a piezoelectric support beam and there is no need to take capacitance between the substrate and the substrate as in the conventional example, the vibrating portion can be separated from the substrate, and large driving displacement and detection displacement can be achieved. Can be taken.

According to the second aspect of the present invention, the driving support beam vibrates in the horizontal direction, and the detection support beam detects vertical vibration based on the Coriolis force. Since the mechanical resonance frequency of the vertical vibration is matched, the drive displacement is large and the detection sensitivity of the Coriolis force with respect to the rotational angular velocity is increased.

Further, according to the present invention, since the pair of driving support beams and the detection support beam are uniaxially arranged, the structure is simplified.

According to the third aspect of the present invention, since the oxide film is provided as a reinforcing material between the front and back surfaces and the middle layer electrode, warpage is prevented, mechanical Q is improved, bending vibration is increased, and temperature change is caused. Is also prevented from changing the mechanical resonance frequency, and the detection sensitivity is improved.

[Brief description of the drawings]

FIG. 1 is a perspective view of a first embodiment of an angular velocity sensor according to the present invention.

FIG. 2 is a perspective view of an outer support beam shown in FIG. 1;

FIG. 3 is a sectional view taken along line x1-x1 of the outer support beam shown in FIG. 2;

FIG. 4 is a perspective view of a second embodiment of the angular velocity sensor of the present invention.

5 is a sectional view showing the polarization direction and the driving electric field direction of the driving support beam shown in FIG.

FIG. 6 is a diagram of the vibration of the driving support beam shown in FIG. 4;

FIG. 7 is a view showing the form of vibration of the detection support beam shown in FIG.

FIG. 8 is a sectional view showing the polarization direction and the detection electric field direction of the detection support beam shown in FIG.

FIG. 9 shows one manufacturing process of the angular velocity sensor of the present invention, and is a process diagram of forming a lower electrode on an oxide film provided on a substrate.

FIG. 10 is also a process chart for forming a lower piezoelectric film.

FIG. 11 is also a process diagram of etching and removing an unnecessary portion of the piezoelectric film.

FIG. 12 is also a process chart of forming an intermediate layer electrode.

FIG. 13 is a process chart of forming an upper piezoelectric film and removing an unnecessary portion of the piezoelectric film.

FIG. 14 is also a process chart for forming an upper electrode.

FIG. 15 is also a process chart for forming an oxide film and removing an unnecessary portion of the oxide film.

FIG. 16 is a process chart for etching and removing the center of the back surface of the substrate.

FIG. 17 is a sectional view of another supporting beam.

FIG. 18 is a view showing another manufacturing process of the angular velocity sensor of the present invention, in which split electrodes of a driving support beam and a detection support beam are provided at opposing portions on both surfaces of a PZT substrate.

FIG. 19 is a process chart of forming a vibrator and a support beam at the center of the PZT substrate.

FIG. 20 is a cross-sectional view of a P processed similarly to the shape shown in FIG.
Process diagram for bonding two ZT substrates

FIG. 21 is a perspective view of a conventional angular velocity sensor.

[Explanation of symbols]

1, 11 Substrate 1a, 11a, 21a Hollow part 2, 12 Frame 2a, 2b, 12a, 12b Frame side 3a, 3b Outer support beam 4 Outer vibration frame 4a, 4b, 4c, 4d Frame side 4e Inside 5a, 5b Inside Support beam 6 Inner vibrator 13a, 13b, 23a, 23b Support beam 14, 22 Vibrator r1 to r4 Vibration region 10, 20 Angular velocity sensor s1, s2 Oxide film z1, z2 Zinc oxide d1, d2, d7a Upper electrode d3, d4 , D7b Middle layer electrode d5, d6 d7c Lower layer electrode d7, d8 Split electrode 21 PZT substrate j Central axis

Claims (3)

[Claims] 1. An outer vibrating frame supported in a hollow portion of a substrate through a pair of opposing outer supporting beams, and a pair of opposing internals disposed inside the outer vibrating frame. An inner vibrator supported via an inner support beam of the outer support beam and the inner support beam, wherein each of the outer electrodes and the inner support beams has an inner electrode and an upper and lower surface of the piezoelectric film, and a central axis of the beams. An angular velocity sensor comprising a multilayer electrode structure divided and arranged on both sides of a vertical plane passing through the sensor. 2. A vibrating body supported in a hollow portion of a substrate via a pair of supporting beams disposed opposite to each other, wherein the supporting beam has a structure in which each layer electrode has the inside of the piezoelectric film and the front and back surfaces thereof. A multi-layer electrode structure divided and arranged on both sides of a vertical plane passing through the central axis of the beams, one supporting beam is for driving to vibrate in the horizontal or vertical direction, and the other supporting beam is An angular velocity sensor characterized in that the beam is used for detecting vertical or horizontal vibration. 3. An oxide film is formed between the front and back surfaces of the support beam and between the middle layer electrodes, and inside the outer vibrating frame, the inner vibrating body, and the vibrating body. Angular velocity sensor.