CN103322995B - Piezoelectric Driving electrostatic detection bulk acoustic resonance three axle microthrust test and preparation method thereof - Google Patents

Abstract

The invention relates to a three-axis micro-gyroscope driven by piezoelectricity and electrostatic detection volume acoustic resonance and a preparation method thereof, comprising: a piezoelectric disk vibrator without a release hole, a cylindrical support column, and gyroscopes distributed on the disk vibrator driving electrodes, and detection electrodes, balance electrodes and common electrodes distributed on the substrate. The driving electrodes are distributed on the disc vibrator; the detection electrodes, balance electrodes and common electrodes are distributed on the substrate and located below the disc vibrator in a circular manner, and are parallel to the disc vibrator and have a Gap; the gyro utilizes the piezoelectric effect for gyro drive. At the same time, the non-contact balanced electrode is used to apply a potential to the lower electrode, so that the structure of the gyroscope is optimized. The manufacturing method of the micro-gyroscope adopts the MEMS processing technology, the manufacturing technology is simple, the reliability is high, and the low cost and high yield can be guaranteed. The invention has the advantages of small volume, simple structure and easy realization of processing technology, and is suitable for mass production.

Description

Piezoelectric-driven electrostatic detection bulk acoustic resonance three-axis micro-gyroscope and preparation method thereof

technical field

The present invention relates to a micro-gyroscope in the field of micro-electromechanical technology and a preparation method thereof, in particular to a three-axis micro-gyroscope with a disk-shaped resonator utilizing bulk acoustic wave saddle resonance mode and its Preparation.

Background technique

Gyroscope is an inertial device that can be sensitive to the angle or angular velocity of the carrier, and it plays a very important role in the fields of attitude control, navigation and positioning. With the development of national defense technology and aviation and aerospace industries, the requirements of inertial navigation systems for gyroscopes are also developing in the direction of low cost, small size, high precision, high reliability, and adaptability to various harsh environments.

After searching the literature of the existing technology, it was found that the Chinese patent "Double-axis MEMS gyroscope" (patent application number: 201020033300.7) uses MEMS bulk silicon and bonding technology to process a cantilever beam structure with springs and mass blocks on silicon wafers with cavity structure. By applying a voltage signal of a single specific frequency to the upper and lower electrodes and the mass block, an electrostatic force is applied to the mass block to cause the mass block to vibrate. When there is an external angular velocity input, under the action of Coriolis force, the vibration will be transferred to another axis, and the change of angular velocity can be detected by detecting the electrode capacitance.

This technology has the following disadvantages: the gyroscope adopts the traditional spring-mass structure model, the signal sensitivity obtained is not high, the Q value is low, the zero drift is too large, the impact resistance is poor, and it is difficult to achieve high precision.

Contents of the invention

The object of the present invention is to address the deficiencies of the prior art, and provide a piezoelectric-driven electrostatic detection body acoustic wave resonant three-axis micro-gyroscope and a preparation method thereof. The gyroscope uses the piezoelectric effect to drive the gyroscope, and at the same time uses a non-contact balance electrode to apply a potential to the lower electrode, so that the gyroscope structure is optimized. The gyroscope is small in size, simple in structure, high in quality factor, easy to implement in processing technology, compatible with CMOS technology, resistant to impact, does not need vacuum packaging, and is suitable for mass production.

According to one aspect of the present invention, there is provided a piezoelectric-driven electrostatic detection bulk acoustic resonance three-axis micro-gyroscope, which includes: a piezoelectric disc vibrator without a release hole, a cylindrical support column, a substrate, a driving electrode, and a detection electrode , balanced electrode and common electrode. The disc vibrator is fixed on the substrate through the cylindrical support column, and the disc vibrator is perpendicular to the z-axis of the substrate; the driving electrodes are distributed on the disc vibrator; the detection electrodes , the balanced electrode and the common electrode are circumferentially distributed on the substrate and located below the disc vibrator, and are parallel to the disc vibrator with a gap; the common electrode is distributed between the balanced electrode and the detection electrode, so The detection electrodes, the balance electrodes and the common electrodes are distributed in a cross cycle according to the arrangement order of two balance electrodes, one common electrode, two detection electrodes, one common electrode, and two balance electrodes.

Preferably, the driving electrodes are distributed on the upper surface of the disc vibrator, and the lower surface of the disc vibrator is a conductor, and is fixed on the substrate through the supporting pillars.

Preferably, the driving electrodes are distributed on the disc vibrator in a circumferential distribution.

Preferably, the gap between the detection electrode, the balance electrode, the common electrode and the disk oscillator is 2-3 microns.

Preferably, every two adjacent balanced electrodes form a group, and a group of DC driving voltage signals of equal magnitude and opposite sign are respectively applied. Each set of balancing electrodes forms a capacitor for balancing the lower surface of the disc vibrator to maintain zero potential.

Preferably, every two adjacent detection electrodes form a group, and a group of DC driving voltage signals of equal magnitude and opposite sign and a group of AC carrier signals of equal magnitude and opposite phase are respectively applied. Each group of driving electrodes forms a capacitor for detecting piezoelectric force to drive the disc vibrator to generate a detection mode.

According to another aspect of the present invention, a kind of manufacture method of above-mentioned microgyro is provided, and its steps are as follows:

(a) Clean the substrate, dry it, and form a metal electrode by sputtering on the front side through a photolithography process;

(b) depositing a polysilicon layer on the substrate with a thickness of 2-3 microns;

(c) Etching the polysilicon layer through a photolithography mask, retaining the supporting columns and the barrier layer;

(d) Clean the other piezoelectric substrate, dry it, and form a metal electrode by sputtering on the front side through a photolithography mask process;

(e) sputtering depositing a metal layer on the back of the piezoelectric substrate;

(f) Laser cutting, using a bonding method to bond two substrates to form an integrated structure.

The present invention uses the saddle-shaped resonance mode of the disk vibrator as a reference vibration. In this mode, the disk vibrator vibrates along the Z-axis direction perpendicular to the surface of its disk, and also along the X-axis in the radial direction of the disk. and vibrate in the Y-axis direction. When the disc vibrator in the X-axis direction moves along the positive direction of the Z-axis perpendicular to its disc surface, the disc vibrator in the Y-axis direction moves along the negative direction of the Z-axis perpendicular to the disc surface thereof. This movement produces a saddle-like effect, which is referred to as the "bulk acoustic saddle mode". By applying a driving voltage to the driving electrodes on the surface of the disc vibrator, a piezoelectric signal is applied to the disc vibrator to excite the disc vibrator to generate a driving mode. The vibration along the Z axis is mainly used to sense the angular velocity of the X and Y axes. When there is an angular velocity input parallel to the X-axis or Y-axis on the surface of the disc vibrator, under the action of Coriolis force, the disc vibrator is subjected to a rotational moment, and the disc vibrator will move along a direction perpendicular to the Z The axial direction rotates around the cylindrical support column. Wherein, the size of the angle of rotation is proportional to the size of the input angle. The vibration along the radial X and Y axes is mainly used to sense the angular velocity of the Z axis. When there is an angular velocity input from the Z-axis perpendicular to the surface of the disk vibrator, under the action of the Coriolis force, the disk vibrator is subjected to a rotational moment, and the disk vibrator will rotate in a direction perpendicular to the Z-axis The cylindrical support column rotates. At this time, the capacitance near the detection electrode will change, and the carrier signal is applied to the detection electrode and extracted from the common electrode. By demodulating the carrier signal, the change in the capacitance near the detection electrode can be obtained, that is, the rotation angle perpendicular to the disk oscillator can be detected, and then the angular velocity input of the three axes can be obtained.

Compared with the prior art, the present invention has the following beneficial effects:

The invention utilizes the bulk acoustic wave saddle-shaped resonant mode and adopts the disk vibrator without release holes, and has simple structure and good symmetry. The gap between the balance electrode, the detection electrode and the common electrode and the disc vibrator is micron level, which is completed by a bonding process, and the process is easy to realize. The lower surface of the disk vibrator does not need to be connected to electrodes, but uses a set of balanced electrode signals of the same size and opposite signs to maintain its zero potential, and detects it through the carrier signal, which reduces the complexity of the processing technology. The present invention uses the vibration in the bulk acoustic wave saddle resonance mode as the reference vibration, uses the capacitance change between the disc vibrator and the detection electrode as the detection signal, and can accurately detect the three input signals by processing the carrier output signal extracted by the common electrode. The magnitude of the axis input angular velocity. The invention adopts MEMS processing technology, has simple manufacturing technology, high reliability, and can guarantee lower cost and higher yield.

Description of drawings

Other characteristics, objects and advantages of the present invention will become more apparent by reading the detailed description of non-limiting embodiments made with reference to the following drawings:

Fig. 1 is a schematic diagram of the structure of the present invention.

Fig. 2 is a three-dimensional perspective view of the structure of the present invention.

Fig. 3 is a left view of the structure of the present invention.

Fig. 4 is a schematic diagram of the BAW saddle resonance mode of the disk vibrator in the present invention.

Fig. 5 is a schematic diagram of the driving mode of the disk vibrator in the present invention.

Fig. 6 is a schematic diagram of the detection mode of the disk vibrator in the present invention.

In the figure: 1 disk vibrator, 2 support columns, 3 substrate, 4 drive electrodes, 5 detection electrodes, 6 balance electrodes, 7 common electrodes.

detailed description

The present invention will be described in detail below in conjunction with specific embodiments. The following examples will help those skilled in the art to further understand the present invention, but do not limit the present invention in any form. It should be noted that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention. These all belong to the protection scope of the present invention.

As shown in Figure 1, Figure 2 and Figure 3, the present embodiment includes:

A piezoelectric disc vibrator 1 without a release hole;

a support column 2 located at the center below the disc vibrator 1;

Substrate 3;

a driving electrode 4 located on the disc vibrator 1;

With the detection electrode 5, the balance electrode 6 and the common electrode 7 located on the substrate 3;

The detection electrode 5 , the balance electrode 6 and the common electrode 7 are distributed on the substrate 3 and located below the disc vibrator 1 , and are parallel to the disc vibrator 1 with a gap therebetween.

In this embodiment, the disc vibrator 1 is made of piezoelectric material, the driving electrodes 4 are distributed on the upper surface, the lower surface of the disc vibrator 1 is a conductor, and is fixed on the on substrate 3.

The lower surface of the vibrator is electroplated with a metal conductive layer, and is fixed on the substrate 3 through the supporting pillars 2 .

In this embodiment, there are eight driving electrodes 4 in total, which are distributed on the upper surface of the piezoelectric disc vibrator 1 in a circumferential distribution. An AC drive signal is applied to the drive electrodes to generate a piezoelectric force, which is used to excite the disc vibrator to generate a drive mode.

In this embodiment, the detection electrode 5, the balance electrode 6 and the common electrode 7 are distributed below the disk vibrator 1 perpendicular to the z-axis of the substrate 3, and are located on the substrate 3 in the form of Circumferential distribution. The gap between the detection electrode 5, the balance electrode 6, the common electrode 7 and the piezoelectric disc vibrator 1 is 2-3 microns, according to the balance electrode, balance electrode 6, common electrode 7, detection electrode, The detection electrode 5, the common electrode 7, the balance electrode, the balance electrode 6, the common electrode 7, the detection electrode, the detection electrode 5, the common electrode 7... are distributed in a cross cycle.

In this embodiment, there are four pairs of balance electrodes 6 , which are respectively located in the positive and negative directions of the X axis and the positive and negative directions of the Y axis. A group of DC driving voltage signals of equal magnitude and opposite sign are respectively applied to each pair of the balanced electrodes 6 . Each pair of the balancing electrodes forms a capacitor for balancing the lower surface of the disc vibrator to maintain zero potential.

In this embodiment, there are four pairs of detection electrodes 5 , which are respectively located at the balance electrodes 6 with an angle difference of 45°. Each pair of detection electrodes 5 is respectively applied with a set of DC driving voltage signals of equal magnitude and opposite sign and a set of AC carrier signals of equal magnitude and opposite phase. Each group of detection electrodes forms a capacitor for detecting piezoelectric force to drive the disc vibrator to generate a detection mode.

In this embodiment, there are eight common electrodes 7 , which are respectively located between each pair of the balancing electrodes 6 and the detection electrodes 5 , and all the common electrodes 7 are connected together. The common electrode 7 is used to extract and detect the carrier signal on the detection electrode 5, and obtain the detection capacitance through a subsequent circuit.

As shown in Figure 4, the bulk acoustic saddle resonance mode of the disc vibrator is obtained by means of finite element analysis, and in this mode, the disc vibrator moves along the Z-axis perpendicular to the surface of the disc vibrator 1 direction vibration. When the disk vibrator 1 in the X-axis direction moves along the Z-axis positive direction perpendicular to the surface of the disk vibrator, the disk vibrator 1 in the Y-axis direction moves along the Z-axis perpendicular to the surface of the disk vibrator movement in the negative direction.

As shown in Fig. 5 and Fig. 6, by applying a driving voltage to the driving electrode 4 on the upper surface of the piezoelectric disk vibrator 1, the piezoelectric force is applied to the disk vibrator 1 to excite the disk vibrator 1 to generate a driving mode. state. The vibration along the Z axis is mainly used to sense the angular velocity of the X and Y axes. When there is an input of angular velocity parallel to the X-axis or Y-axis parallel to the surface of the disk vibrator 1, under the action of the Coriolis force, the disk oscillator 1 is subjected to a rotational moment, and the disk oscillator 1 will move along the Rotate around the cylindrical support column 2 in a direction perpendicular to the Z axis. Wherein, the size of the angle of rotation is proportional to the size of the input angle. The vibration along the radial X and Y axes is mainly used to sense the angular velocity of the Z axis. When an angular velocity of the Z axis perpendicular to the surface of the disk vibrator 1 is input, under the action of the Coriolis force, the disk oscillator 1 is subjected to a rotational moment, and the disk oscillator 1 will move along the cylindrical The support column 2 rotates. At this time, the capacitance near the detection electrode 5 will change. By applying a carrier signal to the detection electrode 5 , the carrier signal is extracted from the common electrode 7 . The change of the capacitance near the detection electrode 5 can be obtained by demodulating the carrier signal, that is, the rotation angle perpendicular to the disk oscillator 1 can be detected, and then the angular velocity input of the three axes can be obtained.

The present embodiment relates to the preparation technology of microgyroscope, mainly comprises the following several steps:

(a) Clean the substrate, dry it, and form a metal electrode by sputtering on the front side through a photolithography process;

(b) depositing a polysilicon layer on the substrate with a thickness of 2-3 microns;

(c) Etching the polysilicon layer through a photolithography mask, retaining the supporting columns and the barrier layer;

(d) Clean the other piezoelectric substrate, dry it, and form a metal electrode by sputtering on the front side through a photolithography mask process;

(e) sputtering depositing a metal layer on the back of the piezoelectric substrate;

(f) Laser cutting, using a bonding method to bond two substrates to form an integrated structure.

The invention utilizes the bulk acoustic wave saddle-shaped resonant mode and adopts the disk vibrator without release holes, and has simple structure and good symmetry. The gap between the balance electrode, the detection electrode and the common electrode and the disc vibrator is micron level, which is completed by a bonding process, and the process is easy to realize. The lower surface of the disk vibrator does not need to be connected to electrodes, but uses a set of balanced electrode signals of the same size and opposite signs to maintain its zero potential, and detects it through the carrier signal, which reduces the complexity of the processing technology. The present invention uses the vibration in the bulk acoustic wave saddle resonance mode as the reference vibration, uses the capacitance change between the disc vibrator and the detection electrode as the detection signal, and can accurately detect the three input signals by processing the carrier output signal extracted by the common electrode. The magnitude of the axis input angular velocity. The invention adopts MEMS processing technology, has simple manufacturing technology, high reliability, and can guarantee lower cost and higher yield.

Specific embodiments of the present invention have been described above. It should be understood that the present invention is not limited to the specific embodiments described above, and those skilled in the art may make various changes or modifications within the scope of the claims, which do not affect the essence of the present invention.

Claims (8)

1. a Piezoelectric Driving electrostatic detection bulk acoustic resonance three axle microthrust test, is characterized in that comprising: the piezo disc oscillator not with release aperture, columniform support column, substrate, drive electrode, detecting electrode, counter electrode and public electrode; Described disc oscillator is fixed on substrate by described columniform support column, and described disc oscillator is perpendicular to the z-axis of described substrate; Described drive electrode is distributed on described disc oscillator; Described detecting electrode, counter electrode and public electrode to be circumferentially distributed on described substrate and to be positioned at below described disc oscillator, simultaneously parallel with described disc oscillator and have a gap; Described public electrode is distributed between counter electrode and detecting electrode, and described detecting electrode, described counter electrode and described public electrode are according to the cross-circulation distribution that puts in order of two counter electrodes, a public electrode, two detecting electrodes, a public electrode, two counter electrodes.

2. Piezoelectric Driving electrostatic detection bulk acoustic resonance three axle microthrust test according to claim 1, it is characterized in that: described disc oscillator upper surface distributes described drive electrode, described disc oscillator lower surface is electric conductor, and fixing on the substrate by described support column.

3. Piezoelectric Driving electrostatic detection bulk acoustic resonance three axle microthrust test according to claim 1, is characterized in that: described drive electrode is distributed on piezo disc oscillator, circumferentially distributes.

4. Piezoelectric Driving electrostatic detection bulk acoustic resonance three axle microthrust test according to claim 1, is characterized in that: described detecting electrode, described counter electrode and the gap between described public electrode and described disc oscillator are 2-3 micron.

5. Piezoelectric Driving electrostatic detection bulk acoustic resonance three axle microthrust test according to claim 1, it is characterized in that: every two adjacent described counter electrodes are one group, apply one group of contrary driving DC voltage signal of equal and opposite in direction symbol respectively, each is organized described counter electrode and forms an electric capacity, for balancing the electromotive force of described disc oscillator lower surface, described disc oscillator lower surface is made to keep zero potential.

6. Piezoelectric Driving electrostatic detection bulk acoustic resonance three axle microthrust test according to claim 1, it is characterized in that: every two adjacent described detecting electrodes are one group, apply one group of contrary driving DC voltage signal of equal and opposite in direction symbol and the contrary one group of ac-excited signal of equal and opposite in direction phase place respectively, each is organized described drive electrode and forms an electric capacity, drives described disc oscillator to produce sensed-mode for detecting piezoelectric forces.

7. the Piezoelectric Driving electrostatic detection bulk acoustic resonance three axle microthrust test according to any one of claim 1-6, it is characterized in that: described gyro utilizes the saddle type resonance mode of disc oscillator as reference vibration, under this mode, described disc oscillator vibrates along the Z-direction perpendicular to its disc surfaces, simultaneously also can along disk diameter to X-axis and Y direction vibration, when the described disc oscillator of X-direction moves along the Z axis positive dirction perpendicular to its disc surfaces, the described disc oscillator of Y direction moves along the Z axis negative direction perpendicular to its disc surfaces, by applying driving voltage on described disc oscillator surface drive electrode, piezoelectric signal being applied to described disc oscillator and encourages described disc oscillator to produce driven-mode, when there being the turning rate input of X-axis or the Y-axis being parallel to described disc oscillator surface, under corioliseffect, described disc oscillator is subject to the effect of a turning moment, described disc oscillator can rotate along perpendicular to Z-direction around described columniform support column, wherein, the angular dimension of rotation is directly proportional with the size of input angle, when there being the turning rate input perpendicular to the Z axis on described disc oscillator surface, under corioliseffect, described disc oscillator is subject to a turning moment effect, described disc oscillator can rotate along perpendicular to Z-direction around described columniform support column, capacitance size now near described detecting electrode can change, by applying carrier signal on described detecting electrode, and from described public electrode, carrier signal is extracted, carrier signal obtains the size variation of electric capacity near described detecting electrode by demodulation, namely the anglec of rotation perpendicular to described disc oscillator is detected, and then try to achieve the turning rate input size of three axles.

8. a preparation method for the Piezoelectric Driving electrostatic detection bulk acoustic resonance three axle microthrust test as described in any one of claim 1-7, is characterized in that comprising the steps:

A () is clean by base-plate cleaning, dry, and in front by photoetching process, sputtering forms metal electrode;

B () be deposition of polysilicon layer on substrate, thickness is 2-3 micron;

C (), by mask, etches polycrystalline silicon layer, retains support column and restraining barrier;

D another piezoelectric substrate cleans up by (), dry, and in front by mask technique, sputtering forms metal electrode;

E () is at piezoelectric substrate back spatter depositing metal layers;

F () cut, utilizes the method for bonding by two pieces of substrate bondings, form the structure of integration.