CN109470228B - MEMS (micro-electromechanical system) disc gyroscope based on embedded differential electrode and preparation method thereof - Google Patents
MEMS (micro-electromechanical system) disc gyroscope based on embedded differential electrode and preparation method thereof Download PDFInfo
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- CN109470228B CN109470228B CN201811279399.6A CN201811279399A CN109470228B CN 109470228 B CN109470228 B CN 109470228B CN 201811279399 A CN201811279399 A CN 201811279399A CN 109470228 B CN109470228 B CN 109470228B
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01C—MEASURING DISTANCES, LEVELS OR BEARINGS; SURVEYING; NAVIGATION; GYROSCOPIC INSTRUMENTS; PHOTOGRAMMETRY OR VIDEOGRAMMETRY
- G01C19/00—Gyroscopes; Turn-sensitive devices using vibrating masses; Turn-sensitive devices without moving masses; Measuring angular rate using gyroscopic effects
- G01C19/56—Turn-sensitive devices using vibrating masses, e.g. vibratory angular rate sensors based on Coriolis forces
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- B81—MICROSTRUCTURAL TECHNOLOGY
- B81B—MICROSTRUCTURAL DEVICES OR SYSTEMS, e.g. MICROMECHANICAL DEVICES
- B81B7/00—Microstructural systems; Auxiliary parts of microstructural devices or systems
- B81B7/02—Microstructural systems; Auxiliary parts of microstructural devices or systems containing distinct electrical or optical devices of particular relevance for their function, e.g. microelectro-mechanical systems [MEMS]
Abstract
The invention discloses an MEMS (micro-electromechanical systems) disc gyroscope based on an embedded differential electrode and a preparation method thereof. The structure is formed by processing a single crystal silicon material, and comprises: the gyroscope comprises a gyroscope sensitive structure and an electrode embedded in the plane of the sensitive structure; the gyro sensitive structure comprises: the gyro comprises a central anchor point and N concentric rings taking the center of the anchor point as the circle center, wherein the central anchor point is used for fixing a gyro sensitive structure, the concentric rings are connected with the anchor point and the rings through spokes, and the spokes and the concentric rings jointly form a movable elastic structure of the gyro. According to the invention, a large number of electrodes are embedded in the annular sensitive structure, so that the area of the capacitor is greatly increased, and the detection precision is improved. Meanwhile, the embedded electrodes appear in pairs, so that differential detection and differential driving can be realized, and the linearity and the anti-interference capability of the gyroscope are improved.
Description
Technical Field
The invention relates to the technical field of MEMS (Micro-Electro Mechanical System) sensors, in particular to an MEMS disc gyroscope based on embedded differential electrodes.
Background
In recent years, MEMS gyroscopes have become hot spots in inertial sensors due to their advantages of low power consumption, small size, low cost, etc. As a special angular velocity sensor, the MEMS annular gyroscope has the advantages of mass, rigidity and central symmetry of resonance frequency due to the fact that the structure of the MEMS annular gyroscope has the characteristic of circumferential symmetry, is good in mode matching performance and strong in overload resistance, and becomes an important research direction of military MEMS gyroscopes.
However, the precision of the existing MEMS annular gyroscope is generally not high, and the requirement of tactical precision is difficult to achieve. The zero-bias stability, zero-bias repeatability and the like of the existing MEMS annular gyroscope are greatly influenced along with the environmental temperature, and the MEMS annular gyroscope cannot adapt to complex and variable application environments.
Disclosure of Invention
The technical problem to be solved by the invention is as follows: the defects of the prior art are overcome, the MEMS disc-shaped gyroscope based on the embedded differential electrode is provided, and compared with the prior art, the gyroscope detection precision is improved.
The technical solution of the invention is as follows: a MEMS disk gyroscope based on embedded differential electrodes, the MEMS disk gyroscope comprising: the gyroscope comprises a gyroscope sensitive structure and an electrode embedded in the plane of the sensitive structure;
the gyro sensitive structure comprises: the gyroscope comprises a central anchor point and N concentric rings with the center of the anchor point as the center of a circle, wherein the central anchor point is used for fixing a gyroscope sensitive structure, the concentric rings are connected with the anchor point and the rings through spokes, the spokes radiate outwards by taking the center of the anchor point as the center, the space between two adjacent rings is divided into 8 sections of grooves according to an equal circumferential angle of 45 degrees, two adjacent layers of spokes are distributed in a whole staggered manner at an angle of 22.5 degrees from inside to outside, and the spokes and the concentric rings jointly form a movable elastic structure of the gyroscope;
the embedded electrodes include four types: the first mode driving electrode, the first mode detecting electrode, the second mode driving electrode and the second mode detecting electrode are embedded and distributed in each groove formed by each adjacent concentric circular ring and each spoke.
The first mode driving electrode, the first mode detection electrode, the second mode driving electrode and the second mode detection electrode are all differential electrodes, and two differential ends of the same electrode are located in the same groove.
The first mode driving electrode and the first mode detection electrode are distributed in the grooves in the directions of 0 degree, 90 degrees and 180 degrees and 270 degrees; the second mode driving electrodes and the second mode detecting electrodes are distributed in the grooves in the directions of 45 degrees, 135 degrees, 225 degrees and 315 degrees.
The first mode driving electrode and the first mode detecting electrode are distributed in the grooves in the directions of 45 degrees, 135 degrees, 225 degrees and 315 degrees; the second mode driving electrode and the second mode detecting electrode are distributed in the grooves in the directions of 0 degrees, 90 degrees, 180 degrees and 270 degrees.
The first mode driving electrode and the second mode driving electrode are arranged in the groove close to the circle center; the first mode detection electrode and the second mode detection electrode are arranged in the groove far away from the circle center.
One side of two differential ends of the same electrode in the same groove, which is close to the center of the center anchor point, and the other side of the two differential ends, which is far away from the center of the center anchor point, are opposite to each other in the positions of the two differential ends of the same type of electrodes in the mutually vertical direction.
The MEMS disc gyroscope also comprises a first modal amplitude-stabilizing driving closed-loop control circuit, wherein the first modal amplitude-stabilizing driving closed-loop control circuit comprises a first differential detection circuit, a phase discriminator circuit, an amplitude discriminator circuit, a phase integration circuit, an amplitude integration circuit and a first modal differential driving circuit module;
differential signals S1+ and S1-collected by two differential ends of the first mode detection electrode are divided into two paths after signal summation and amplification are realized through the first differential detection circuit, and one path is subjected to phase demodulation through the phase discriminator circuit to obtain a phase signal; the other path realizes amplitude demodulation through an amplitude discriminator circuit to obtain an amplitude signal; the phase signal and the amplitude signal respectively pass through a phase integrating circuit and an amplitude integrating circuit) and are multiplied to obtain a first modal driving signal, the first modal driving signal is converted into a pair of differential driving signals D1+ and D1-with equal amplitude and opposite phase through a first differential driving circuit module, and the differential driving signals are respectively applied to the positive phase end and the negative phase end of the first modal differential driving electrode to form closed-loop feedback driving so as to realize resonant frequency tracking and amplitude stabilization control. .
The MEMS disc gyroscope also comprises a second modal angular velocity driving closed-loop control circuit, wherein the second modal angular velocity driving closed-loop control circuit comprises a second differential detection circuit, an in-phase demodulation circuit, an orthogonal demodulation circuit, an angular rate integration circuit, a coupling integration circuit and a second modal differential driving circuit module;
differential signals S2+ and S2-collected by two differential ends of the second modal detection electrode are divided into two paths after summation and amplification of the signals are realized through a second differential detection circuit, and one path of signals is demodulated through an in-phase demodulation circuit to obtain an angular rate signal; the other path realizes the demodulation of the coupling signal through an orthogonal demodulation circuit to obtain a coupling signal; the angular rate signal and the coupling signal are respectively passed through an angular rate integrating circuit and a coupling integrating circuit and added to obtain a second modal driving signal, the second modal driving signal is converted into a pair of differential driving signals D2+ and D2-which have equal amplitude and opposite phases through a second modal differential driving circuit module, and the differential driving signals are respectively applied to the positive phase end and the negative phase end of the second modal differential driving electrode to form closed-loop feedback control, so that angular rate detection and coupling signal suppression are realized.
The other technical solution of the invention is as follows: a preparation method of an MEMS (micro-electromechanical systems) disc gyroscope based on an embedded differential electrode comprises the following steps:
s1, etching the through hole of the substrate silicon wafer by adopting deep reactive ion etching;
s2, oxidizing the substrate silicon wafer subjected to through hole etching, forming insulating layers inside the through hole and on the upper surface of the silicon wafer, and filling the through hole with a conductor;
s3, depositing a metal layer on the surface of one side of the substrate, and making the metal layer fully contact with the conductor in the through hole; carrying out graphical etching on the metal layer, and reserving an area which needs to be in contact with an anchor point and an electrode of the gyro device layer and an area which needs to form a metal connecting line;
s4, step etching is carried out on the device layer silicon, the raised part of the step is an anchor point and an electrode which need to be bonded, and then gold-silicon bonding is carried out on the device layer silicon and the substrate layer;
s5, deep silicon etching is carried out on the device layer silicon to form a gyro sensitive structure;
s6, depositing a metal layer on the surface of one side of the cap layer silicon, and carrying out graphical etching, wherein the reserved area is a bonding area needing to form a closed bond;
s7, etching a cavity on the cap layer silicon, and growing a getter in the cavity;
s8, carrying out gold-silicon bonding on the cap layer silicon and the device layer silicon in a vacuum environment to form a closed cavity;
and S9, finally thinning the substrate silicon to expose the conductor on the outer surface of the substrate.
The metal layer is a chromium-nickel-gold or titanium-nickel-gold alloy layer.
Compared with the prior art, the invention has the beneficial effects that:
(1) the disc gyroscope is provided with the concentric rings, a large number of detection electrodes can be placed in the grooves among the concentric rings, and compared with the traditional annular gyroscope, the area of a detection capacitor can be increased by one to two orders of magnitude, and the detection precision of the gyroscope can be greatly improved due to the increase of the detection capacitor;
(2) the disk gyroscope of the invention adopts differential electrodes. The differential detection electrode can effectively inhibit the influence of environmental interference such as common-mode vibration, temperature drift and the like, and the detection precision of the gyroscope is improved;
(3) the differential driving electrode of the invention also improves the vibration linearity of the gyroscope in the working mode, and is beneficial to improving the precision.
Drawings
FIG. 1 is a schematic structural diagram of an MEMS disc gyroscope based on an embedded differential electrode according to an embodiment of the present invention;
FIG. 2 is a schematic view of a first modal electrode distribution according to an embodiment of the present invention;
FIG. 3 is a schematic view of a second modal electrode distribution according to an embodiment of the present invention;
FIG. 4 is a schematic diagram of a gyroscope closed-loop control method according to an embodiment of the present invention;
FIG. 5 is a schematic view of a processing structure of a spinning top according to an embodiment of the present invention;
FIG. 6(a) is a schematic diagram of etching a silicon via of a gyro substrate according to an embodiment of the present invention;
FIG. 6(b) is a schematic illustration of filling a silicon via of a gyro substrate according to an embodiment of the present invention;
FIG. 6(c) is a schematic diagram of a silicon metal layer of a gyroscope substrate according to an embodiment of the present invention;
FIG. 6(d) is a schematic diagram of the Au-Si bonding of the gyroscope device layer and the substrate layer according to the embodiment of the invention;
FIG. 6(e) is a schematic diagram illustrating etching of a gyroscope sensitive structure according to an embodiment of the present invention;
FIG. 6(f) is a schematic view of the layer-by-layer metal fabrication of a top cap layer according to an embodiment of the present invention;
FIG. 6(g) is a schematic diagram of etching a deep trench in a top cap layer and fabricating a getter according to an embodiment of the invention;
FIG. 6(h) is a schematic diagram of bonding of a top cap layer and a device layer and thinning of a substrate according to an embodiment of the invention.
Detailed Description
The invention is described in detail below with reference to the figures and specific examples.
The invention provides an MEMS (micro-electromechanical system) disc gyroscope structure based on an embedded differential electrode, and particularly innovations are made on the design of the electrode. The present invention will be described in further detail with reference to the accompanying drawings.
FIG. 1 is a schematic plan view of a MEMS disc gyroscope device layer structure based on an embedded differential electrode. As shown in fig. 1, the MEMS disc gyroscope structure based on embedded differential electrodes of the present invention includes: a gyro-sensitive structure 100 made up of a plurality of concentric rings and spokes, and an electrode 104 embedded within the plane of the ring-sensitive structure. The device structure layer material is generally <111> monocrystalline silicon, and the device thickness is generally 100 μm-350 μm.
The gyro sensor structure 100 mainly includes: center anchor point 101, N concentric ring 102 with the anchor point center as the centre of a circle, wherein, center anchor point is used for fixed top sensitive structure, the number of concentric ring generally is more than 5 (containing 5), concentric ring uses the center of anchor point as the centre of a circle, regular distribution is around the anchor point, concentric ring and anchor point, be connected through the spoke between ring and the ring, the spoke uses the anchor point centre of a circle to outwards radiate as the center, the spoke is connected ring and anchor point, ring and ring, constitute the movable elastic construction of top jointly.
The spokes of the gyro sensitive structure divide the space between two adjacent circular rings into 8 sections of grooves according to an equal circumferential angle of 45 degrees, each group of the grooves is distributed around a central anchor point at an equal angle, and two adjacent layers of the spokes are integrally distributed in a staggered manner at an angle of 22.5 degrees from inside to outside. The gap between two adjacent rings becomes the annular groove, and same annular groove equidistance equiangular distribution 8 spokes, and the spoke of two adjacent annular grooves is not adjacent, and the contained angle difference with the central point is 22.5. The movable mass block and the spring structure of the gyroscope are formed by connecting the spokes and the circular ring together, and the mass and the spring are combined into a whole. The spokes are distributed at equal circumferential angles, and divide the grooves of the gyroscope into 8. For placing the embedded electrodes 104 of both modalities. The corresponding directions of 0 degrees, 90 degrees and 180 degrees, 270 degrees are first modal directions; the 45 °, 135 °, 225 °, 315 ° directions are second mode directions. Or the directions of 0 degrees, 90 degrees and 180 degrees, 270 degrees are second modal directions; the 45 °, 135 °, 225 °, 315 ° directions are the first mode directions.
The MEMS disk gyroscope includes a plurality of embedded electrodes 104 distributed in respective trenches formed by adjacent concentric rings and spokes, the electrodes comprising: the device comprises a first mode driving electrode, a first mode detection electrode, a second mode driving electrode and a second mode detection electrode. And the electrodes in each trench appear in pairs to form differential electrodes.
Both modes include drive electrodes, sense electrodes. Wherein the drive electrodes are generally placed in the grooves near the center of the circle and the sense electrodes are generally placed in the grooves far from the center of the circle. Namely: if the directions of 0 degree, 90 degree and 180 degree 270 degree are first mode directions, and the directions of 45 degree, 135 degree, 225 degree and 315 degree are second mode directions, the first mode driving electrode is arranged on the groove close to the circle center in the directions of 0 degree, 90 degree and 180 degree 270 degree; a first mode detection electrode is arranged in a groove which is far away from the center of a circle in the directions of 0 degrees, 90 degrees and 180 degrees and 270 degrees; a second modal driving electrode is placed in a groove close to the center of a circle in the directions of 45 degrees, 135 degrees, 225 degrees and 315 degrees; and second mode detection electrodes are arranged in the grooves which are far away from the center of the circle in the directions of 45 degrees, 135 degrees, 225 degrees and 315 degrees.
Setting: the first mode driving electrode, the first mode detection electrode, the second mode driving electrode and the second mode detection electrode are all differential electrodes, and two differential ends of the same electrode are located in the same groove. The direction of the electrode close to the circle center is the 'inner side direction', and the direction of the electrode far away from the circle center is the 'outer side direction'; the same type of electrodes (e.g., first mode drive electrodes) are in mutually perpendicular directions, and the direction of the differential electrodes of the same polarity (e.g., positive end of the first mode drive electrodes) is "opposite", that is: if the normal phase terminal electrode of the first mode drive electrode is the "inner direction" in the directions of 0 ° and 180 °, the direction of the normal phase terminal electrode of the first mode drive electrode is the "outer direction" in the directions of 90 ° and 270 °. Other classes of electrodes and so on. The same-polarity electrodes in the eight directions of the two modes are connected in parallel through the metal wiring layer.
Fig. 2 is a schematic view of the electrode distribution in the first mode. As shown in fig. 2, the first mode electrodes are distributed in the trenches in the directions of 0 °, 90 °, 180 ° and 270 °; the first modal driving electrode is arranged in four grooves which are vertical to each other and close to the circle center; the first mode detection electrode is arranged in four grooves which are far away from the center of a circle in the mutually perpendicular direction. And the driving electrode and the detection electrode are both differential electrodes. The same type of electrodes (e.g. first mode drive electrodes) are in mutually perpendicular directions, and the direction of the differential electrodes of the same polarity (e.g. positive side of the first mode drive electrodes) is "opposite".
Fig. 3 is a schematic diagram of the electrode distribution in the second mode. As shown in fig. 2, the second mode electrodes are distributed in the grooves in the directions of 45 °, 135 °, 225 °, 315 °; the second modal driving electrode is arranged in four grooves which are vertical to each other and close to the circle center; the second mode detection electrode is arranged in four grooves which are perpendicular to each other and far away from the circle center. And the driving electrode and the detection electrode are both differential electrodes. The same type of electrodes (e.g. first mode drive electrodes) are in mutually perpendicular directions, and the direction of the differential electrodes of the same polarity (e.g. positive side of the first mode drive electrodes) is "opposite".
FIG. 4 is a schematic block diagram of a closed-loop control of a MEMS disk gyroscope based on embedded differential electrodes. As shown in FIG. 2, the closed-loop control system of the disc gyroscope comprises a first-mode amplitude-stabilized driving closed-loop control circuit and a second-mode closed-loop detection control circuit.
The first-mode amplitude-stabilized driving closed-loop control circuit comprises a first-mode amplitude-stabilized driving closed-loop control circuit, and the first-mode amplitude-stabilized driving closed-loop control circuit comprises a first difference detection circuit 401, a phase detector circuit 402, an amplitude detector circuit 404, a phase integration circuit 403, an amplitude integration circuit 405 and a first-mode difference driving circuit module 406.
Differential signals S1+ and S1-collected by two differential ends of the first mode detection electrode are divided into two paths after signal summation and amplification are realized through the first differential detection circuit 401, and one path is subjected to phase demodulation through the phase discriminator circuit 402 to obtain a phase signal; the other path realizes amplitude demodulation through an amplitude discriminator circuit 404 to obtain an amplitude signal; the phase signal and the amplitude signal are multiplied by the phase integrating circuit 403 and the amplitude integrating circuit 405 respectively to obtain a first modal driving signal, the first modal driving signal is converted into a pair of differential driving signals D1+ and D1-with equal amplitude and opposite phase by the first differential driving circuit module 406, and the differential driving signals are applied to the positive phase end and the negative phase end of the first modal differential driving electrode respectively to form closed-loop feedback driving, so that resonant frequency tracking and amplitude stabilization control are realized. The closed loop detection circuit can be realized by an analog circuit or a digital circuit.
The second modal angular velocity driving closed-loop control circuit comprises a second differential detection circuit 501, an in-phase demodulation circuit 502, a quadrature demodulation circuit 504, an angular rate integration circuit 503, a coupling integration circuit 505 and a second modal differential driving circuit module 506.
Differential signals S2+ and S2-collected by two differential ends of the second modal detection electrode are divided into two paths after summation and amplification of the signals are realized through the second differential detection circuit 501, and one path is demodulated through the in-phase demodulation circuit 502 to obtain an angular rate signal; the other path realizes the demodulation of the coupling signal through an orthogonal demodulation circuit 504 to obtain a coupling signal; the angular rate signal and the coupling signal are respectively passed through the angular rate integrating circuit 503 and the coupling integrating circuit 505 and added to obtain a second modal driving signal, the second modal driving signal is converted into a pair of differential driving signals D2+ and D2-with equal amplitude and opposite phase by the second modal differential driving circuit module 506, and the differential driving signals are respectively applied to the positive phase end and the negative phase end of the second modal differential driving electrode to form closed-loop feedback control, so that angular rate detection and coupling signal suppression are realized.
The invention also provides a processing method of the embedded differential electrode MEMS disc gyroscope, and the cross section of the embedded differential electrode MEMS disc gyroscope is shown in FIG. 5. As shown in fig. 6(a) to 6(h), the specific steps include:
s1: as shown in fig. 6(a), deep reactive ion etching is used to etch through holes on the substrate silicon wafer 2; the thickness of the substrate silicon wafer is generally not less than 200 μm, and the diameter of the through hole is generally less than 100 μm;
s2: as shown in fig. 6(b), the substrate silicon wafer 2 which has undergone via etching is oxidized to form an insulating layer (3) inside the via and on the upper surface of the silicon wafer, and then the via is filled with a conductor, typically polysilicon or copper, to form a via filling material 4;
s3: as shown in fig. 6(c), a metal layer 5 is deposited on one side surface of the substrate, and the metal layer is brought into sufficient contact with and electrically conducted to the conductor in the via hole; on one hand, the metal layer is used for carrying out gold-silicon bonding with the electrode and the anchor point of the device layer silicon, and on the other hand, a metal connecting line is formed to connect the electrodes with the same polarity in parallel; carrying out graphical etching on the metal layer, and reserving an area which needs to be in contact with an anchor point and an electrode of the gyro device layer and an area which needs to form a metal connecting line; the metal layer is typically a chromium-nickel-gold or titanium-nickel-gold alloy layer;
s4: as shown in fig. 6(d), step etching is performed on the device layer silicon 100, and the raised portions of the steps are anchors and electrodes to be bonded; then carrying out gold-silicon bonding with the substrate layer; the height of the step is generally 10um to 50 um.
S5: as shown in fig. 6(e), deep silicon etching is performed on the device layer silicon 100 to release the sensitive structure, and the movable structure is separated from the electrode by etching to form the gyro sensitive structure 100;
s6: as shown in fig. 6(f), depositing a metal layer 5 on one surface of the cap layer silicon 6, and performing patterned etching, wherein the reserved area is a bonding area required to form a hermetic bond; the metal layer is typically a chromium-nickel-gold or titanium-nickel-gold alloy layer;
s7: as shown in fig. 6(g), a cavity is etched in the cap layer silicon 6, and a getter 7 is grown in the cavity;
s8: as shown in fig. 6(h), in a vacuum environment, the cap layer silicon 6 and the device layer silicon 100 are gold-silicon bonded to form a closed cavity;
and S9, finally thinning the substrate silicon 2 to expose the conductor on the outer surface of the substrate.
Parts of the specification which are not described in detail are within the common general knowledge of a person skilled in the art.
Claims (7)
1. A MEMS dish top based on embedded differential electrode is characterized by comprising: the gyroscope comprises a gyroscope sensitive structure (100), an electrode (104) embedded in the plane of the sensitive structure, a first modal amplitude-stabilizing drive closed-loop control circuit and a second modal angular velocity drive closed-loop control circuit;
the gyroscopic sensitive structure (100) comprises: the gyroscope comprises a central anchor point (101) and N concentric rings (102) with the center of the anchor point as the center of a circle, wherein the central anchor point is used for fixing a gyroscope sensitive structure, the concentric rings are connected with the anchor point and the rings through spokes, the spokes radiate outwards with the center of the anchor point as the center, the space between two adjacent rings is divided into 8 sections of grooves according to an equal circumferential angle of 45 degrees, two adjacent layers of spokes are distributed in a whole staggered manner at 22.5 degrees from inside to outside, and the spokes and the concentric rings jointly form a movable elastic structure of the gyroscope;
the embedded electrodes (104) include four types: the first mode driving electrode, the first mode detection electrode, the second mode driving electrode and the second mode detection electrode are embedded and distributed in each groove formed by each adjacent concentric ring (102) and each spoke (103);
the first-mode amplitude-stabilized driving closed-loop control circuit comprises a first differential detection circuit (401), a phase discriminator circuit (402), an amplitude discriminator circuit (404), a phase integration circuit (403), an amplitude integration circuit (405) and a first-mode differential driving circuit module (406);
differential signals S1+ and S1-collected by two differential ends of the first mode detection electrode are divided into two paths after signal summation and amplification are realized through a first differential detection circuit (401), and one path is subjected to phase demodulation through a phase discriminator circuit (402) to obtain a phase signal; the other path realizes amplitude demodulation through an amplitude discriminator circuit (404) to obtain an amplitude signal; the phase signal and the amplitude signal are multiplied through a phase integrating circuit (403) and an amplitude integrating circuit (405) respectively to obtain a first modal driving signal, the first modal driving signal is converted into a pair of differential driving signals D1+ and D1-with equal amplitude and opposite phases through a first differential driving circuit module (406), and the differential driving signals are applied to the positive phase end and the negative phase end of a first modal differential driving electrode respectively to form closed-loop feedback driving so as to realize resonant frequency tracking and amplitude stabilization control;
the second modal angular velocity driving closed-loop control circuit comprises a second differential detection circuit (501), an in-phase demodulation circuit (502), a quadrature demodulation circuit (504), an angular velocity integration circuit (503), a coupling integration circuit (505) and a second modal differential driving circuit module (506);
differential signals S2+ and S2-collected by two differential ends of the second modal detection electrode are divided into two paths after summation and amplification of the signals are realized through a second differential detection circuit (501), and one path of signals is demodulated through an in-phase demodulation circuit (502) to obtain an angular rate signal; the other path realizes the demodulation of the coupling signal through an orthogonal demodulation circuit (504) to obtain a coupling signal; the angular rate signal and the coupling signal are respectively added through an angular rate integrating circuit (503) and a coupling integrating circuit (505) to obtain a second modal driving signal, the second modal driving signal is converted into a pair of differential driving signals D2+ and D2-with equal amplitude and opposite phases through a second modal differential driving circuit module (506), and the differential driving signals D2+ and D2-are respectively applied to a positive phase end and a negative phase end of a second modal differential driving electrode to form closed-loop feedback control, so that angular rate detection and coupling signal suppression are realized.
2. The MEMS disc gyroscope according to claim 1, wherein the first mode driving electrode, the first mode detecting electrode, the second mode driving electrode and the second mode detecting electrode are all differential electrodes, and two differential ends of the same electrode are located in the same trench.
3. The MEMS disc gyroscope according to claim 1, wherein the first mode driving electrodes and the first mode detecting electrodes are distributed in the grooves in the directions of 0 °, 90 ° and 180 ° and 270 °; the second mode driving electrodes and the second mode detecting electrodes are distributed in the grooves in the directions of 45 degrees, 135 degrees, 225 degrees and 315 degrees.
4. The MEMS disc gyroscope of claim 1, wherein the first mode driving electrodes and the first mode detecting electrodes are distributed in the grooves in the directions of 45 °, 135 °, 225 ° and 315 °; the second mode driving electrode and the second mode detecting electrode are distributed in the grooves in the directions of 0 degrees, 90 degrees, 180 degrees and 270 degrees.
5. The MEMS disc gyroscope of claim 1, wherein the first mode driving electrode and the second mode driving electrode are disposed in a groove near the center of the circle; the first mode detection electrode and the second mode detection electrode are arranged in the groove far away from the circle center.
6. The MEMS disc gyroscope of claim 1, wherein: one of two differential ends of the same electrode in the same groove is close to the circle center of the central anchor point (101), and the other differential end is far away from the circle center of the central anchor point (101), and the positions of the two differential ends of the same type of electrodes in the mutually perpendicular direction are opposite.
7. The method for preparing the MEMS disc gyroscope based on the embedded differential electrode according to claim 1 is characterized by comprising the following steps:
s1, etching the through hole of the substrate silicon wafer (2) by adopting deep reactive ion etching;
s2, oxidizing the substrate silicon wafer (2) subjected to through hole etching, forming an insulating layer (3) in the through hole and on the upper surface of the silicon wafer, and then filling the through hole with a conductor;
s3, depositing a metal layer (5) on one side surface of the substrate, and making the metal layer fully contact with the conductor in the through hole; carrying out graphical etching on the metal layer, and reserving an area which needs to be in contact with an anchor point and an electrode of the gyro device layer and an area which needs to form a metal connecting line; the metal layer is a chromium-nickel-gold or titanium-nickel-gold alloy layer;
s4, step etching is carried out on the device layer silicon (100), the protruding part of the step is an anchor point and an electrode which need to be bonded, and then gold-silicon bonding is carried out on the device layer silicon (100) and the substrate layer;
s5, deep silicon etching is carried out on the device layer silicon (100) to form a gyro sensitive structure (100);
s6, depositing a metal layer (5) on the surface of one side of the cap layer silicon (6), and carrying out graphical etching, wherein the reserved area is a bonding area needing to form closed bonding;
s7, etching a cavity on the cap layer silicon (6), and growing a getter (7) in the cavity;
s8, performing gold-silicon bonding on the cap layer silicon (6) and the device layer silicon (100) in a vacuum environment to form a closed cavity;
and S9, finally thinning the substrate silicon (2) to expose the conductor on the outer surface of the substrate.
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