JPH08145687A - Angular speed measuring apparatus and manufacture thereof - Google Patents

Abstract

PURPOSE: To obtain a thin angular speed measuring apparatus which can be formed by a semiconductor process technology. CONSTITUTION: An angular speed detection axis is set in the direction normal to the plane of a base 1 exhibiting piezoelectricity and a set of surface wave excitation/detection system, comprising an exciting means 2 for generating a surface acoustic wave, means 4 for reflecting the surface acoustic wave and changing the traveling direction thereof and means 3 for detecting the surface acoustic wave, is formed on the surface and rear of the base 1. A surface acoustic wave, i.e., a Rayleigh wave generated from the exciting means 2, propagates through the reflection means 5 and enters the detection means 3 and the planar Rayleigh waves propagate in the opposite directions on the surface and the rear.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an angular velocity measuring device for detecting an angular velocity when an object rotates, and more particularly to an angular velocity measuring device utilizing surface acoustic waves and a manufacturing method thereof.

[0002]

2. Description of the Related Art Heretofore, as an angular velocity measuring device using a surface acoustic wave, there has been known one disclosed in Japanese Patent Laid-Open No. 62-148812 or USP-4,384,409.

A conventional example will be described with reference to FIG.

The gyro device of FIG. 6 has a rotating base 21.
On the surface of the base 21 parallel to the angular velocity detection axis 22, a plurality of comb-teeth electrodes 24 and 25 formed by means of photolithography or the like are formed.
At this time, the mass point moves in the direction perpendicular to the angular velocity detection axis 22 on the surface of the surface acoustic wave propagation.

The plurality of comb-teeth electrodes 24, 25 are electrodes that combine both excitation and detection. The surface acoustic waves excited by the electrodes propagate in opposite directions, and the base 21
After being propagated around the circumference of the circle, it is detected again by the electrodes 24 and 25. At this time, the angular velocity Ω around the angular velocity detection axis 22
In the case of = 0, the propagation path length L of each surface acoustic wave propagating in the opposite direction is the same, and no phase difference occurs.

When an angular velocity around the angular velocity detection axis is applied,

[0007]

[Outside 1]

The mass point receives the Coriolis force represented by, and the phase propagation velocity V1 of the surface acoustic wave propagating in the first direction,
It changes to the phase propagation velocity V2 of the surface acoustic wave propagating in the second direction. Therefore, a phase difference proportional to the angular velocity is obtained in the signal detected by the detection comb-teeth electrode.

Further, by amplifying the signal obtained by the comb-teeth electrode for detection and feeding it back to the excitation electrode,
When forming a feedback loop, this circuit acts as an oscillator. At this time, the oscillation frequency f is

[0010]

[Equation 1]

It oscillates at a frequency that satisfies the following matching condition.

A change in the phase propagation velocity due to the addition of the angular velocity around the detection axis to this oscillator is detected as a change in the oscillation frequency.

[0013]

In the conventional angular velocity measuring device described above, the plurality of comb-teeth electrodes are formed on a plane parallel to the angular velocity detecting axis of the base, that is, on the side surface of the base. ing.

Therefore, there is a limit to reduction in thickness.

It is not suitable for fabrication by semiconductor process technology.

There is a problem that

The present invention solves such conventional problems,
It is an object of the present invention to provide a thin angular velocity measuring device that can be formed by a semiconductor process technique and a manufacturing method thereof.

[0018]

SUMMARY OF THE INVENTION An angular velocity measuring apparatus for achieving the object of the present invention has an angular velocity detection axis perpendicular to a piezoelectric plane of a base, and a surface acoustic wave is placed on the plane. Surface acoustic wave excitation means for generating, and reflection means for reflecting the surface acoustic waves to change the traveling direction thereof,
It is characterized in that at least two sets of surface wave excitation / detection systems, each of which includes a detection means for detecting the surface acoustic wave, are formed.

In this structure, the surface acoustic wave propagates on the plane of the base, the direction of the surface acoustic wave is changed by the reflecting means, and the surface of the base is effectively used to lengthen the propagation path length to increase the detection sensitivity. Can be increased. Therefore, the device can be made thinner.

In the above structure, the surface wave excitation / detection system can be formed on both sides of the base, or two sets can be formed on one side, which increases the degree of freedom in design.

The surface acoustic wave may be a Rayleigh wave, and the Rayleigh wave generated by the exciting means propagates so as to enter the detecting means via the reflecting means, and at least one of which propagates in opposite directions. In a configuration having a set of the Rayleigh waves, for example, a configuration in which a surface wave excitation / detection system is formed on the front and back surfaces, the propagation directions of the Rayleigh waves are opposite to each other around the angular velocity detection axis, and the propagation paths are on the same plane. In the configuration in which the lengths are different, the propagation directions of the Rayleigh waves are opposite to each other around the angular velocity detection axis.

Thus, when the angular velocity is generated, the angular velocity can be obtained by measuring the phase difference between both Rayleigh waves by the measuring means, and the output signal which is the excitation signal of the surface acoustic wave detected by the detecting means can be obtained. It is possible to obtain the angular velocity by measuring the change in frequency with the measuring means.

By configuring the propagation distance of the Rayleigh wave to be an integral multiple of the wavelength, the angular velocity can be favorably detected by utilizing the above-mentioned phase difference or frequency change.

On the other hand, in the angular velocity measuring device having the above structure, the base, the exciting means, the reflecting means, and the detecting means can be formed by the semiconductor process technology.

[0025]

【Example】

 <First Embodiment> FIG. 1 shows a first embodiment of the present invention.

FIG. 1A is a perspective view of the structure of the first embodiment, in which 1 is PZT, LiNbO ₃ , Z.
A piezoelectric substance such as nO, 2 is a comb-teeth electrode for excitation, and 3 is a comb-teeth electrode for detection. Reference numeral 4 is a reflector that is arranged at an angle of 45 ° with respect to the traveling direction of the surface acoustic wave in order to bend the surface acoustic wave propagating on the surface of the piezoelectric body by 90 °. The reflector is realized by forming an electrode for each quarter of the wavelength λ of the surface acoustic wave or forming a groove in the piezoelectric body 1 by a technique such as etching. With this structure, the surface acoustic wave circulates in a plane perpendicular to the angular velocity detection axis 100. In addition, FIG.
FIG. 2 is a perspective view of the opposite surface of FIG.
Similarly, the comb-teeth electrode 5 for excitation, the comb-teeth electrode 6 for detection, and the reflector 7 are formed on the surface opposite to the above. However, at this time, the first surface acoustic wave 8 propagating on the upper surface of the piezoelectric body 1,
The propagation directions of the second surface acoustic wave 9 propagating on the back surface are opposite to each other.

When the angular velocity Ω is applied around the axis of the detection shaft 100, the surface acoustic wave propagating on the surface of the piezoelectric body receives a force and its phase propagation velocity changes. Assuming that the change in the phase propagation velocity due to the angular velocity Ω is ΔV, the phase propagation velocity of the first surface acoustic wave 8 propagating in the same direction as the rotation direction is V + ΔV
In addition, the phase propagation velocity of the second surface acoustic wave 9 propagating in the opposite direction changes to V-ΔV.

At this time, the phase delay φ of the first surface acoustic wave 8
₁ and the phase delay φ ₂ of the _second surface acoustic wave 9 is

[0029]

[Equation 2]

The phase difference between the signals detected by the detection comb-teeth electrodes 3, 6 is detected by the phase detector 10. The phase difference is the difference in the phase propagation velocities of the surface acoustic waves, 2Δ.
It becomes larger in proportion to V and the propagation distance L of the surface acoustic wave, and it is preferable to increase the propagation path length in order to improve the sensitivity. Therefore, a feature of this embodiment is that a reflector is provided on the surface of the piezoelectric body and each surface acoustic wave is circulated to increase the propagation distance and enhance the sensitivity.

Further, since the comb-teeth electrodes for excitation and detection are provided on the upper and lower surfaces of the substrate, the thickness can be made thin.

<Second Embodiment> FIG. 2 illustrates a second embodiment of the present invention. The same parts as those in the first embodiment are designated by the same reference numerals.

In this embodiment, a plurality of surface acoustic waves propagating in opposite directions propagate in the same plane, not in the upper and lower surfaces of the substrate as in the first embodiment. In this case, a plurality of surface acoustic waves 8,
The respective propagation path lengths L ₁ and L _{2 of 9} have a relationship of L ₁ > L ₂ .

At this time, the phase delay φ of the first surface acoustic wave 8
₁ and the phase delay φ ₂ of the _second surface acoustic wave 9 is

[0035]

(Equation 3)

Is represented by

When Ω = 0, since the phases of the signals detected by the comb-teeth electrodes 3 and 6 for detection are the same, the difference in propagation path length L ₁ -L ₂ is the center of propagation of the surface acoustic wave. It needs to be an integral multiple of the wavelength λ at the frequency f ₀ .

<Third Embodiment> FIG. 3 shows a third embodiment of the present invention. The same parts as those in the first embodiment are designated by the same reference numerals.

In the figure, 11 is a comb electrode 3 for detection.
This is an amplifier for amplifying the obtained signal and feeding it back to the comb electrode 2 for input. At this time, if the gain of the signal returned to the input comb electrode 2 is larger than 1, this circuit functions as an oscillator, the output terminal, the interval between the comb electrodes 12 and the velocity of the surface acoustic wave propagating on the substrate. A signal having a frequency determined by V is obtained. The sharpness of the oscillation of this oscillator, that is, the Q value reaches the order of several thousands to tens of thousands, and the purity of the oscillation is very high.

In the third embodiment, similarly to the first embodiment, when the angular velocity Ω is applied in the direction of the angular velocity detection axis 100, the first surface acoustic wave 8 and the second surface acoustic wave 9 propagating in circulation are circulated. Each phase propagation velocity changes to V + ΔV and V−ΔV. Therefore, the oscillation frequency changes to f + Δf and f−Δf, and the oscillation / frequency change proportional to the input angular velocity is obtained, and Δf is detected by counting the output from the output terminal 12 with the frequency counter 13. .

As shown in FIG. 4, it is conceivable that a plurality of surface acoustic waves propagating in opposition to each other are formed on the same plane, not on the upper and lower sides of the substrate, as in the second embodiment. Also in this case, the difference L between the propagation path lengths of the surface acoustic waves 8 and 9 is L
_It goes without saying that ₁₋ L ₂ needs to be an integral multiple of the wavelength λ at the oscillation center frequency f ₀ .

<Fourth Embodiment> FIG. 5 shows a fourth embodiment of the present invention and is a sectional view showing a process of an angular velocity measuring apparatus.

In FIG. 5A, 31 is a Si substrate, and the <110> plane and the <111> plane are oriented in the directions shown in the figure. In FIG. 5 (b), SiO with an electrode pattern drawn
₂ Form a mask. After that, when wet etching is performed with a KOH aqueous solution or the like, the vertical grooves shown in FIG. 5C are formed on the <111> plane and the <110> plane because the etching speed is anisotropic.

After removing the mask, as shown in FIG. 5D, A1 is sputtered in this groove to form an electrode on the back surface side. Then, as shown in FIG. 5 (e), a piezoelectric material such as PZT or ZnO is formed on the surface of the substrate by means such as vapor deposition or sputtering. At this time, a hole for selectively etching the substrate on the back surface side is provided. deep.

After the A1 electrode was formed again on the surface of the substrate by sputtering, the Si substrate was changed to H as shown in FIG. 5 (f).
The electrode is exposed by performing isotropic etching with a NO ₃ aqueous solution or the like.

By the method described above, it is possible to manufacture an angular velocity measuring device using semiconductor process technology. Needless to say, the angular velocity measuring device of the present invention can be manufactured by another semiconductor process.

[0047]

According to the invention described in claim 1, the surface acoustic wave propagates on the plane of the base, and the direction of the surface acoustic wave is changed by the reflecting means. Moreover, since the propagation path length is lengthened by effectively utilizing the surface of the base, the detection sensitivity can be increased.

According to the second and third aspects of the present invention, the surface wave excitation / detection system can be formed on both sides of the base, or two sets can be formed on one side, and the design is free. As a result, the size of the device can be further reduced.

According to the invention described in claim 4, the surface acoustic wave can be a Rayleigh wave, and the Rayleigh wave generated by the exciting means propagates so as to enter the detecting means via the reflecting means. , A configuration having at least one set of Rayleigh waves propagating in opposite directions, for example, in a configuration in which a surface wave excitation / detection system is formed on the front and back surfaces, the propagation directions of Rayleigh waves are opposite to each other around the angular velocity detection axis. Next to
For example, in the configuration formed by different propagation path lengths on the same plane, the propagation directions of Rayleigh waves can be opposite to each other around the angular velocity detection axis, and by using a general surface wave The device can be realized with a simple configuration.

According to the fifth and sixth aspects of the invention, when the angular velocity is generated, the angular velocity can be obtained by measuring the phase difference between both Rayleigh waves by the measuring means, and the elasticity detected by the detecting means. It is possible to obtain the angular velocity by measuring the change in the frequency of the output signal which is the excitation signal of the surface wave by the measuring means, and it is possible to detect the angular velocity with high accuracy.

According to the seventh aspect of the present invention, by configuring the propagation distance of the Rayleigh wave to be an integral multiple of the wavelength, the angular velocity can be detected by utilizing the above-mentioned phase difference or frequency change. You can do well.

According to the eighth aspect of the invention, in the angular velocity measuring device having the above structure, the base, the excitation means, the reflection means, and the detection means can be formed by the semiconductor process technology.

[Brief description of drawings]

FIG. 1 is a perspective view showing a first embodiment of the present invention, FIG.
Shows the front side, and (b) shows the back side surface of the base.

FIG. 2 is a perspective view showing a second embodiment.

FIG. 3 is a perspective view showing a third embodiment, wherein (a) shows a front surface side and (b) shows a rear surface of the base.

FIG. 4 is a perspective view showing a modification of the third embodiment.

FIG. 5 is a cross-sectional view of the manufacturing process showing the fourth embodiment.

FIG. 6 is a perspective view of a conventional angular velocity measuring device.

[Explanation of symbols]

1 ... Piezoelectric body 2, 3, 5, 6
... comb-teeth electrodes 4, 7 ... reflectors 8, 9 ... surface acoustic waves 100 ... angular velocity detection axis

Claims (8)

[Claims] 1. An angular velocity detection axis is set in a direction perpendicular to a plane having piezoelectricity of a base, and a surface acoustic wave excitation means for generating a surface acoustic wave on the plane, and a surface acoustic wave reflecting the surface acoustic wave for reflecting the surface acoustic wave. An angular velocity measuring device characterized in that at least two sets of surface wave excitation / detection systems, each of which includes a reflection unit for changing a traveling direction and a detection unit for detecting the surface acoustic wave, are formed. 2. The angular velocity measuring device according to claim 1, wherein the surface wave excitation / detection system is formed on both sides of the base. 3. The angular velocity measuring device according to claim 1, wherein two sets of surface wave excitation / detection systems are formed on one side of the base. 4. The surface acoustic wave according to claim 1, 2 or 3, wherein the surface acoustic wave is a Rayleigh wave, and the Rayleigh wave generated by the exciting means propagates so as to enter the detecting means via the reflecting means, and has opposite directions. An angular velocity measuring device, comprising at least one set of Rayleigh waves propagating in the. 5. The angular velocity is obtained by measuring the phase difference of the output signal, which is the excitation signal of the surface acoustic wave detected by the detecting means, by the measuring means. Angular velocity measuring device. 6. The angular velocity is obtained by measuring the change in frequency of an output signal, which is an excitation signal of a surface acoustic wave detected by the detecting means, by the measuring means. Angular velocity measuring device. 7. The angular velocity measuring device according to claim 4, wherein the propagation distance of the Rayleigh wave is an integral multiple of the wavelength. 8. The method of manufacturing an angular velocity measuring device according to claim 1, wherein the base, the excitation means, the reflecting means, and the detecting means are formed by a semiconductor process technique. .