JPH07103768A - Angular velocity sensor - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide an angular velocity sensor that is small but has high detection capability. [Structure] A vibrator 11 is fixed to the surface of a substrate 1 which is rotated around the x-axis. The central portion of the vibrator 11 has a mass portion 1 vibrated in the direction of arrow A by vibrating means (not shown).
It is 1b. A portion of the surface of the substrate 1 facing the mass portion 11b has a concavo-convex shape that is substantially uniform in the x-axis direction, and the substrate-side electrode 2 is formed on the surface. The shape of the mass part 11b is also a uniform uneven shape in the x-axis direction corresponding to the substrate-side electrode 2,
The vibrator-side electrode 12 is formed at a portion facing the substrate-side electrode 2. As a result, the facing area between the substrate-side electrode 2 and the oscillator-side electrode 12 increases, and the change in the capacitance between the electrodes 2 and 12 when the distance between the electrodes 2 and 12 changes increases. Detectability is improved.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vibration gyro type angular velocity sensor of capacitance detection type.

[0002]

2. Description of the Related Art A vibration gyro is known as a device for detecting the orientation of an object in order to obtain information such as the attitude, movement, and speed of the object. A vibration gyro is smaller than a gyro consisting of a mechanical mechanism that uses the principle of spinning tops, can be manufactured at low cost, and is capable of highly accurate detection. It is expected to be used as a direction detector.

FIG. 9 is a schematic perspective view of a conventional vibration gyro type angular velocity sensor. As shown in FIG. 9, this angular velocity sensor includes a substrate 101 and a fixed portion 111a at one end.
And a vibrator 111 supported by the substrate 101. At the free end, which is the other end of the vibrator 111, the mass portion 11 vibrated in the direction of arrow a by vibrating means (not shown).
1b is integrally provided, and a gap is formed between the mass portion 111b and the substrate 101. Also, the mass part 11
An oscillator-side electrode 112 is provided on the surface of the substrate 1b facing the oscillator 101, while a substrate-side electrode 102 is provided on a portion of the substrate 101 opposed to the oscillator-side electrode 112.

Based on the above configuration, the mass portion 111b of the vibrator 111 is vibrated at a constant frequency in the direction of arrow a by vibrating means, and in this state, the substrate 101 is rotated about the x axis at an angular velocity ω, Coriolis force is generated in the mass portion 111b, and the mass portion 111b vibrates in the direction of arrow b. As a result, the distance between the vibrator-side electrode 112 and the substrate-side electrode 102 changes, and the capacitance between the vibrator-side electrode 112 and the substrate-side electrode 102 changes accordingly. Then, at this time, the angular velocity ω is obtained by measuring the current flowing between the electrodes 102 and 112.

[0005]

However, since the above-mentioned conventional vibration gyro type angular velocity sensor can be manufactured by applying the semiconductor process technology, it has an advantage that miniaturization is achieved, but it is small. However, there is a problem that the detection capability is deteriorated with the progress of the development. This is because the detection capacity of the capacitance-sensing angular velocity sensor depends on the facing area of each electrode, and the facing area of each electrode becomes smaller due to the miniaturization, so that the capacitance due to the vibration of the mass part is reduced. This is because the amount of change, that is, the amount of change in the current flowing between the electrodes is small.

[0006] Therefore, an object of the present invention is to provide an angular velocity sensor having a high detection ability even if it is small.

[0007]

In order to achieve the above object, an angular velocity sensor of the present invention is capable of being displaced through a predetermined gap in a substrate and in one axial direction parallel to the substrate and in a direction perpendicular to the substrate. A supported mass part, a vibrating means for vibrating the mass part in the uniaxial direction, and a pair of planar electrodes provided to face each of the substrate and the mass part. In the angular velocity sensor which is parallel to the substrate and is rotated about an axis perpendicular to the one axis, the pair of electrodes are formed in a concavo-convex shape in a direction perpendicular to the vibration direction of the mass part. Characterize.

The pair of electrodes may be made of silicon having a low resistance.

[0009]

In the angular velocity sensor of the present invention configured as described above, the mass portion supported on the substrate through the predetermined gap is
The vibrating means vibrates in the direction of one axis parallel to the substrate, and in this state, the angular velocity sensor is rotated about an axis parallel to the substrate and perpendicular to the one axis. Then, Coriolis force acts on the mass portion, and the Coriolis force causes the mass portion to vibrate in a direction perpendicular to the substrate. Since the planar electrodes are provided on the substrate and the mass portion so as to face each other, the capacitance between the electrodes changes due to the displacement of the mass portion, and the angular velocity is obtained from this change.

Here, since each electrode is formed in a concavo-convex shape in a direction perpendicular to the vibration direction of the mass part, the facing area of each electrode is large even if the mass part is small. Therefore, the change in the electrostatic capacitance between the electrodes due to the vibration of the mass portion is large, and the detection capability of the angular velocity sensor is improved.

[0011]

Embodiments of the present invention will now be described with reference to the drawings.

(First Embodiment) FIG. 1 is a perspective view of an essential part of a first embodiment of an angular velocity sensor of the present invention, with a part broken away,
FIG. 2 is a plan view of the angular velocity sensor shown in FIG. As shown in FIGS. 1 and 2, the vibrator 11 is fixed to the surface of the substrate 1 rotated about the x-axis. Oscillator 11
Has fixing portions 11a at both ends along the x-axis direction, and is fixed to the substrate 1 at each fixing portion 11a. Further, the center of the vibrator 11 is a mass part 11b composed of the vibrator side electrode 12 and the comb-teeth electrode 11d, and the mass part 11b is provided at both ends with a support integrally extended from each fixing part 11a. It is supported by the beam 11c so as to be displaceable from the surface of the substrate 1 through a predetermined space and in the direction of arrow A which is a direction perpendicular to the x axis.

A portion of the surface of the substrate 1 facing the mass portion 11b has a concavo-convex shape that is substantially uniform in the x-axis direction, and the substrate-side electrode 2 is formed on the surface. Also, the shape of the mass portion 11b is an uneven shape that is substantially uniform in the x-axis direction, corresponding to the substrate-side electrode 2,
The vibrator-side electrode 12 is formed at a portion facing the substrate-side electrode 2.

The angular velocity sensor of this embodiment is manufactured by using a semiconductor process technique as described later, and when a space is formed between the substrate 1 and the mass part 11b in the mass part 11b. The through hole 14 necessary for the above is formed.

Further, as shown in FIG. 2, comb-teeth-shaped electrodes 11d having comb-teeth are formed on both ends of the mass portion 11b, respectively. Drive electrode 1 in the shape of a comb tooth for giving a displacement in the direction
3 is formed. The comb-teeth electrode 11d and the drive electrode 13 of the substrate 1 are shown in FIG. 3 in order to make the width of the vibrator-side electrode 12 shorter than the width of the substrate-side electrode 2 when manufactured in a manufacturing process described later. So that the mass part 11
It is formed at a position higher than b. Transducer side electrode 12
The width of the mass is smaller than that of the substrate-side electrode 2 because
This is to prevent the mass portion 11b from colliding with the substrate 1 when 1b vibrates in the direction of arrow A.

When a voltage is applied to the drive electrode 13 based on the above structure, an electrostatic force is exerted between the drive electrode 13 and the comb-teeth electrode 11d, and this voltage is periodically switched, so that the mass portion 11b has an arrow. It vibrates in the A direction. When the angular velocity sensor is rotated about the x-axis at the angular velocity ω in this state, Coriolis force acts on the mass portion 11b according to the vibration direction of the mass portion 11b, and the mass portion 11b moves in the direction perpendicular to the surface of the substrate 1. It vibrates in the direction of arrow B. As a result, the capacitance between the vibrator-side electrode 12 and the substrate-side electrode 2 changes,
The angular velocity ω is obtained from this change in capacitance. At this time,
Since the substrate-side electrode 2 and the oscillator-side electrode 12 are each in a concavo-convex shape, the opposing area between them is larger than that in the case of a flat plate shape, and the change in electrostatic capacitance due to the vibration of the mass portion 11b. The amount will be large. As a result, the detection capability is improved.

Next, the manufacturing process of the angular velocity sensor of this embodiment will be described with reference to FIG. 4, focusing on the process of forming the uneven shape of the substrate side electrode 2 and the vibrator side electrode 12.

First, as shown in FIG. 4A, a silicon nitride film 15 is formed on the surface of a Si substrate 1 by a low pressure CVD (LPCVD) method, and then photolithography and reactive ion etching are performed. Method is used to remove the silicon nitride film 15 at a pitch equal to the pitch of the irregularities to be formed, and use it as an etching mask. Here, the pitch of the silicon nitride film 15 is set to about 4 μm.

Next, as shown in FIG. 4B, the substrate 1
The surface is etched using a KOH solution at 110 ° C. As a result, the substrate 1 is etched only in the portion where the silicon nitride film 15 does not remain, and the surface of the substrate 1 is formed with irregularities. At this time, the etching depth was about 2 μm at the maximum.

Then, as shown in FIG. 4C, LPC is formed on the etching surface of the substrate 1 including the silicon nitride film 15.
After forming a polysilicon film by the VD method and patterning it, phosphorus is further injected by the ion implantation method to reduce the resistance of the substrate-side electrode forming portion, and the substrate-side electrode 2 having the same shape as the unevenness of the substrate 1 is formed. At this time, the thickness of the substrate-side electrode 2 is
It was set to about 2 μm.

After the substrate side electrode 2 is formed, FIG.
As shown in, the sacrificial layer 16 made of SiO _{2 is formed} on the substrate 1 including the substrate side electrode 2 by the vacuum sputtering method. Then, as shown in FIG.
The positions of d and the drive electrode 13 are raised to make the vibrator side electrode 1
In order to make the width of 2 smaller than the width of the substrate-side electrode 2, the sacrifice layer 16 formed above is etched except for the portions to be the drive electrodes 13 and the comb-teeth electrodes 11d, and the thickness thereof is reduced. To do. The thickness of the sacrificial layer 16 was initially about 6 μm, and was etched to 3 μm.

Next, as shown in FIG. 4E, a polysilicon film of 2.5 is formed on the sacrificial layer 16 by LPCVD.
After forming a film with a thickness of μm and patterning it, phosphorus is implanted by an ion implantation method to form the vibrator-side electrode 12. As a result, the vibrator-side electrode 12 having the same unevenness as the substrate-side electrode 2 is obtained. As described above, by forming the substrate-side electrode 2 and the oscillator-side electrode 12 using low-resistance silicon, thermal and structural stability are superior to metal electrodes such as Au and Al, and the manufacturing process The degree of freedom of is dramatically improved.

Further, the drive electrode 13 and the comb-teeth electrode 11d are formed by reactive etching, and the through-hole 14 for removing the sacrifice layer 16 in a later step is formed in the vibrator-side electrode 12.

Then, the sacrifice layer 16 is removed by etching through the through hole 14 with an aqueous solution of hydrofluoric acid, so that the space between the substrate-side electrode 2 and the oscillator-side electrode 12 is increased as shown in FIG. A void is formed in the.

The angular velocity sensor thus manufactured can have a size of about 4 mm × 4 mm, is small and lightweight, and exhibits high sensitivity. For example, by applying a voltage of 50 V and 100 kHz to the drive electrode 13, a resolution of 5 ° / sec was obtained.

Here, when the unevenness is formed on the substrate 1, K
Although the OH solution is used, the present invention is not limited to this, and reactive ion etching of carbon tetrachloride or sulfur hexafluoride may be used. In addition to forming irregularities on the substrate 1 by partially removing the surface of the substrate 1, the substrate 1 may be formed by vapor deposition, electrodeposition, or the like.
The unevenness may be formed on the substrate 1 by partially depositing a substance on the surface of the substrate. Further, as the material of the substrate 1, another material such as crystal capable of forming irregularities can be used.

(Second Embodiment) FIG. 5 is a plan view of a second embodiment of the angular velocity sensor of the present invention. As shown in FIG. 5, in the angular velocity sensor of this embodiment, the vibrator 61 is fixed by the fixing portion 61a at the central portion of the substrate 51. Further, the vibrator 61 has two mass parts 61b arranged symmetrically with respect to the x-axis as a center line, and each mass part 61b has a fixed part 61b.
The support beams 61c integrally extended from a support the front surface of the substrate 51 via a predetermined space and displaceably in the direction of arrow C perpendicular to the x-axis.

Here, the construction of the vibrating means of the angular velocity sensor of this embodiment will be described with reference to FIGS. 5 and 6.
The portion of the surface of the substrate 51 that faces each of the mass portions 61b is
Each has an uneven shape that is almost uniform in the x-axis direction,
A substrate-side electrode is formed on the surface. Further, the shape of each mass portion 61b is also a substantially uniform concave-convex shape in the x-axis direction corresponding to the substrate-side electrode, and the vibrator-side electrode is formed at the portion facing the substrate-side electrode. Has been done. Furthermore, comb-teeth-shaped comb-teeth electrodes 61d are formed on both ends of each mass portion 61b, and the substrate 51 is provided with a comb-teeth electrode 61d facing each other so as to displace the mass portion 61b in the direction of arrow C. The comb-teeth-shaped drive electrode 63 is formed. The vibrator-side electrode is formed to have a width smaller than that of the substrate-side electrode. This is to prevent the vibrator-side electrode from colliding with the end of the substrate-side electrode when the vibrator-side electrode vibrates in the direction of arrow C. This is because

Based on the above construction, when a voltage is applied to each drive electrode 63 so that each mass portion 61b vibrates in an opposite phase, and the angular velocity sensor is rotated about the x-axis at the angular velocity ω in that state, the mass Coriolis force acts on each mass portion 61b according to the vibration direction of the portion 61b, and vibrates in the direction perpendicular to the surface of the substrate 51 (direction of arrow D). At this time, since the respective mass portions 61b vibrate in opposite phases to each other, the opposite Coriolis forces act on the respective mass portions 61b, and when one mass portion 61b is displaced away from the substrate 51, the other The mass portion 61b of the above is displaced toward the substrate 51. Then, the capacitance between the vibrator-side electrode and the substrate-side electrode changes due to the vibration of each mass portion 61b, and the angular velocity ω is obtained by taking the difference between the capacitances of the two. Also in this embodiment, since the vibrator-side electrode and the substrate-side electrode are each formed in a concavo-convex shape, the opposing area between them becomes large and the amount of change in capacitance also becomes large, so the detection capability is improved.

Next, the manufacturing process of the angular velocity sensor of this embodiment will be described with reference to FIG. 7 focusing on the process of forming the concavo-convex shape of the substrate side electrode and the vibrator side electrode.

First, as in the first embodiment, FIG.
As shown in, a low pressure CVD is performed on the surface of the Si substrate 51.
After the silicon nitride film 65 is formed by the (LPCVD) method, the silicon nitride film 65 is removed by a photolithography method and a reactive ion etching method at a pitch equal to the pitch of the unevenness to be formed, and a mask for etching is used. And

Next, as shown in FIG. 7B, the substrate 5
The surface of 1 is etched by isotropic etching using an etchant having a ratio of hydrofluoric acid: nitric acid: water = 1: 3: 8. As a result, the substrate 51 is etched only in the portion where the silicon nitride film 65 does not remain, and the surface of the substrate 1 is formed with irregularities. The etching depth at this time was about 10 μm at the maximum.

After that, the silicon nitride film 65 is removed by reactive ion etching using carbon tetrachloride, and as shown in FIG. 7C, phosphorus is applied to the substrate side electrode forming portion of the etched surface of the substrate 51. Ion implantation is performed to reduce the resistance of the substrate-side electrode forming portion, and the substrate-side electrode 52 having the same shape as the unevenness of the substrate 51 is formed.

After forming the substrate-side electrode 52, as shown in FIG. 7D, a sacrificial layer 66 made of SiO _{2 is formed} on the substrate 51 including the substrate-side electrode 52 by a vacuum sputtering method. The thickness of the sacrificial layer 66 was 5 μm.

Next, as shown in FIG. 7E, a polysilicon film of 2.5 is formed on the sacrificial layer 66 by the LPCVD method.
After forming a film with a thickness of μm and patterning it, phosphorus is implanted by an ion implantation method to form a vibrator-side electrode 62. As a result, the transducer-side electrode 62 having the same unevenness as the substrate-side electrode 52 is obtained.

Further, the drive electrode 63 (see FIG. 6) and the comb-teeth electrode 61d (see FIG. 6) are formed by reactive etching. At this time, as shown in FIG. 8A, by etching the portion shown by the diagonal lines so that the position of the comb-teeth electrode 61d and the position of the groove 62a of the transducer-side electrode 62 are arranged alternately, The width of the vibrator-side electrode 62 can be made shorter than the width of the substrate-side electrode 52 as shown in FIG.

Then, the sacrifice layer 66 is removed by etching with an aqueous solution of hydrofluoric acid, so that a space is formed between the substrate-side electrode 52 and the oscillator-side electrode 62, as shown in FIG.

The angular velocity sensor thus manufactured can have a size of about 5 mm × 5 mm, is small and lightweight, and exhibits high sensitivity. For example, by applying a voltage of 30 V and 100 kHz to the drive electrode 63, a resolution of 1 ° / sec was obtained.

[0039]

As described above, in the angular velocity sensor of the present invention, the electrodes provided so as to face the mass portion and the substrate are formed in a concavo-convex pattern in a direction perpendicular to the vibration direction of the mass portion. Even if the mass part is small, the facing area of each electrode can be increased, and the detection capability can be improved.

Further, by forming the pair of electrodes with silicon having a low resistance, the thermal and structural stability becomes excellent, and the degree of freedom in the manufacturing process can be dramatically improved.

[Brief description of drawings]

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

FIG. 2 is a plan view of the angular velocity sensor shown in FIG.

3 is a perspective view of the angular velocity sensor shown in FIG. 2 in the vicinity of comb electrodes and drive electrodes.

4A and 4B are cross-sectional views for explaining a step of forming a concavo-convex shape of a substrate and a mass portion of the angular velocity sensor shown in FIG.

FIG. 5 is a plan view of a second embodiment of the angular velocity sensor of the present invention.

6 is a perspective view of the angular velocity sensor shown in FIG. 5 in the vicinity of a comb-shaped electrode and a drive electrode.

7A and 7B are cross-sectional views for explaining a step of forming a concavo-convex shape of a substrate and a mass portion of the angular velocity sensor shown in FIG.

FIG. 8 is a diagram for explaining the positional relationship between the concavities and convexities of the transducer-side electrode and the comb-teeth electrode in the angular velocity sensor shown in FIG.

FIG. 9 is a schematic perspective view of a conventional angular velocity sensor.

[Explanation of symbols]

 1, 51 Substrate 2, 52 Substrate side electrode 11, 61 Transducer 11a, 61a Fixed part 11b, 61b Mass part 11c, 61c Support beam 11d, 61d Comb tooth electrode 12, 62 Transducer side electrode 13, 63 Drive electrode 14 Penetration Hole 15,65 Silicon nitride film 16,66 Sacrificial layer

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Internal reference number FI technical display location C23F 4/00 E 8417-4K

Claims (2)

[Claims] 1. A mass part supported on a substrate so as to be displaceable in a uniaxial direction parallel to the substrate and in a direction perpendicular to the substrate, and a oscillating the mass part in the uniaxial direction. And a pair of planar electrodes provided on the substrate and the mass portion so as to be opposed to each other, respectively, about an axis parallel to the substrate and perpendicular to the one axis. In the rotated angular velocity sensor, the pair of electrodes are formed in a concavo-convex shape in a direction perpendicular to a vibration direction of the mass part. 2. The angular velocity sensor according to claim 1, wherein the pair of electrodes is made of silicon having a low resistance.