A trimmable MEMS ring laser gyroscope and a method of manufacturing the same

Abstract

The application discloses a tunable MEMS ring vibration gyroscope and a manufacturing method thereof. The tunable MEMS ring vibration gyroscope comprises a substrate layer, a MEMS resonant device layer and a cover layer. The MEMS resonant device layer comprises a ring resonator and a fixed electrode assembly. The ring resonator comprises a vibrating circular ring and a support structure arranged in the vibrating circular ring. The support structure comprises a support anchor point and a plurality of elastic support beams. The vibrating circular ring is suspended between the substrate layer and the cover layer. The upper and lower sides of the support anchor point are connected with the cover layer and the substrate layer respectively. A plurality of detection end frequency mass tuning structures and a plurality of coupling mass tuning structures are arranged on the vibrating circular ring. The cover layer is transparent at positions corresponding to the detection end frequency mass tuning structures and the coupling mass tuning structures. The application can realize coupling error adjustment and mode matching through mechanical structure tuning.

Description

Technical Field

[0001] This invention relates to MEMS gyroscopes, and more specifically to an adjustable MEMS ring vibrating gyroscope and its manufacturing method. Background Technology

[0002] MEMS (Micro-Electro-Mechanical Systems) gyroscopes are angular velocity sensors based on the Coriolis effect. They offer advantages such as small size, high reliability, light weight, low power consumption, low cost, and mass production capabilities, making them widely used in aerospace, industrial, automotive electronics, and consumer electronics, with a promising market prospect. MEMS gyroscopes operate with two modes: drive and detection. First, electrostatic excitation puts the drive end into a stable amplitude resonance state. When an external angular velocity is input, the Coriolis effect generates a Coriolis force proportional to the input angular velocity. This force forces the detection end to vibrate. By detecting the change in the vibration displacement of the detection end, the magnitude of the external input angular velocity is sensed. The mechanical sensitivity of a MEMS gyroscope is affected by the structural drive amplitude, the detection Q value, and the frequency difference between the drive and detection modes. A larger drive amplitude, a higher Q value, and a smaller frequency difference result in higher mechanical sensitivity. The main source of error affecting the performance accuracy of MEMS gyroscopes is mechanical coupling error. This error arises from manufacturing errors causing a misalignment between the gyroscope's rigid axis and its motion axis, resulting in an angular deviation. This causes the vibration signal of the driving mode to couple to the detection mode, leading to an orthogonal error signal. Currently, existing MEMS vibrating gyroscopes use electrostatic negative stiffness coefficient control to adjust the coupling stiffness. When the coupling error is large, a large adjustment voltage is required, and dynamic real-time orthogonal control needs to be maintained during gyroscope operation to ensure stable performance. This method requires complex, high-precision detection and control circuits and orthogonal control algorithms.

[0003] MEMS ring gyroscopes, as one of the main technological directions of high-performance MEMS gyroscopes, feature a fully symmetrical structure and typically operate in a degenerate mode with n=2. The driving and detection modes are identical, exhibiting high Q-values, high sensitivity, low noise, and good shock resistance, temperature characteristics, and fabrication robustness. Although MEMS ring gyroscopes typically operate in a degenerate mode with n=2, theoretically possessing the same driving and detection mode frequencies, fabrication errors in MEMS technology prevent perfect synchronization of the driving and detection frequencies, resulting in frequency fragmentation between the two modes. Current MEMS ring gyroscopes employ electrostatic negative stiffness coefficient control to adjust the frequencies of the two modes to achieve mode matching, thereby improving the gyroscope's mechanical sensitivity. However, this method requires a large adjustment DC voltage when there are significant manufacturing errors, and dynamic real-time adjustment is necessary to maintain gyroscope performance stability. This approach demands complex, high-precision detection and control circuits and mode matching algorithms, while the excessively high DC adjustment voltage places high demands on ASIC (Application Specific Integrated Circuit) technology. Existing mechanical coupling error and frequency adjustment methods cannot better meet the application requirements of improving gyroscope accuracy, enhancing environmental adaptability, improving performance consistency, and low-cost mass production.

[0004] Therefore, it is necessary to propose a new method for adjusting the mechanical coupling error, excitation and detection structure frequency based on the mechanism of MEMS ring vibrating gyroscope, in order to solve the problem that the existing MEMS ring vibrating gyroscope is difficult to achieve modal matching and cannot further improve its performance accuracy and environmental adaptability. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide an adjustable MEMS ring gyroscope and its manufacturing method, which can fundamentally improve the symmetry of the structure through mechanical structure adjustment, realize coupling error adjustment and mode matching, improve the signal-to-noise ratio and zero-bias stability of the gyroscope, and at the same time reduce the measurement and control voltage requirements of the back-end ASIC circuit, reduce the complexity of the measurement and control circuit and the requirements of the chip fabrication process, improve the reliability of the circuit, and help improve the reliability and environmental adaptability of the gyroscope.

[0006] An adjustable MEMS ring gyroscope of the present invention includes a base layer, a MEMS resonant device layer and a cap layer;

[0007] The MEMS resonant device layer includes a ring resonator and a fixed electrode assembly. The ring resonator includes a vibrating ring and a support structure disposed within the vibrating ring. The support structure includes a support anchor point and multiple elastic support beams. The two ends of the multiple elastic support beams are respectively connected to the vibrating ring and the support anchor point. The vibrating ring is suspended between the base layer and the cap layer. The support anchor point and the upper and lower sides of the fixed electrode assembly are respectively fixedly connected to the cap layer and the base layer. Multiple detection end frequency quality adjustment structures and multiple coupling quality adjustment structures are arranged circumferentially at intervals on the outer wall of the vibrating ring.

[0008] The cap layer has through holes corresponding to the support anchor point and the fixed electrode assembly, and the electrode layer is disposed in the through holes. The cap layer is transparent at the positions of the detection end frequency quality adjustment structure and the coupling quality adjustment structure.

[0009] Furthermore, multiple detection end frequency quality adjustment structures are equally spaced along the circumference on the outer wall of the vibrating ring, and each detection end frequency quality adjustment structure has a coupling quality adjustment structure on different sides in the circumference.

[0010] Furthermore, the number of detection end frequency quality adjustment structures is four, and the included angle between two adjacent detection end frequency quality adjustment structures is 90°; the number of coupling quality adjustment structures is eight, and each detection end frequency quality adjustment structure is provided with one coupling quality adjustment structure at a 22.5° interval on different sides in the circumferential direction.

[0011] Furthermore, the fixed electrode assembly includes a plurality of inner fixed electrodes independently disposed within the vibrating ring and a plurality of outer fixed electrodes independently disposed outside the vibrating ring.

[0012] Furthermore, the MEMS resonant device layer also includes a closed portion disposed radially outside the external fixed electrode. A first support platform, a second support platform, a third support platform, and a fourth support platform are disposed on the substrate layer. The first support platform is connected to the support anchor point, the second support platform is connected to the internal fixed electrode, the third support platform is connected to the external fixed electrode, and the fourth support platform is connected to the closed portion.

[0013] Furthermore, a second lower groove is provided between the base layer and the second support platform and the third support platform, and a second upper groove is provided between the cap layer and the second lower groove. The second lower groove and the second upper groove are arranged facing each other, and a cavity is formed between the second lower groove and the second upper groove to provide a space for the vibration ring, the detection end frequency quality adjustment structure and the coupling quality adjustment structure.

[0014] The base layer is provided with a first lower groove between the first support platform and the second support platform, and the cap layer is provided with a first upper groove at the position of the first lower groove, with the first lower groove and the first upper groove facing each other.

[0015] The base layer has a third lower groove between the third support platform and the fourth support platform, and the cap layer has a third upper groove at the position of the third lower groove. The third lower groove and the third upper groove are arranged facing each other, and a thin film getter is disposed in the third upper groove.

[0016] Furthermore, the substrate layer includes a silicon wafer layer and an insulating layer disposed on the upper outer surface of the silicon wafer layer.

[0017] The present invention discloses a method for manufacturing an adjustable MEMS ring gyroscope, which includes the following steps:

[0018] S1. Select monocrystalline silicon as the first layer structure, etch the first, second and third under-grooves on it, and make its surface insulated by the insulating layer generation process to form a double-layer structure of silicon wafer layer and insulating layer, and complete the manufacturing of the substrate layer.

[0019] S2. Single-crystal silicon is selected as the second layer structure and bonded to the substrate layer. The ring resonator, fixed electrode assembly, sealing part, multiple detection end frequency quality adjustment structure and multiple coupling quality adjustment structure are etched to complete the fabrication of the MEMS resonant device layer.

[0020] S3. Borosilicate glass is selected as the third layer structure. Through holes, first upper groove, second upper groove and third upper groove are etched out, and a thin film getter is deposited in the first upper groove and third upper groove.

[0021] S4. The component obtained in step S3 is anodicly bonded to the MEMS resonant device layer to form a hermetically sealed vacuum package, and the thin film getter is activated to complete the fabrication of the cap layer.

[0022] S5. Deposit a metal film on the surface of the cap layer, perform photolithography and etching processes to form an electrode layer, and make the positions of the cap layer corresponding to the vibration ring, the detection end frequency quality adjustment structure and the coupling quality adjustment structure transparent to obtain an adjustable MEMS ring vibration gyroscope.

[0023] Furthermore, the manufacturing method further includes:

[0024] S6. Test the gyroscope coupling error signal, gyroscope drive resonant frequency, and detection resonant frequency of the MEMS ring vibrating gyroscope. If the test is qualified, the process ends; if the test is unqualified, proceed to step S7.

[0025] S7. Quality adjustment; specifically including:

[0026] S701. Test the gyroscope coupling error signal Vm of the MEMS ring vibrating gyroscope, compare it with the given error signal reference value V0, and calculate ΔV=Vm-V0;

[0027] S702. By using laser to penetrate the capping layer and adjust the coupling mass of the structure, the coupling mass Δm1 is reduced.

[0028] S703. Retest the gyroscope coupling error signal Vm of the MEMS ring vibrating gyroscope, compare it with the given error signal reference value V0, and recalculate ΔV=Vm-V0; if the recalculated ΔV meets the set error signal requirement, proceed to step S704; otherwise, return to step S702.

[0029] S704. Test the gyroscope drive resonant frequency fd and the detection resonant frequency fs of the MEMS ring vibrating gyroscope, and calculate the frequency difference Δf = fd - fs;

[0030] S705. By using laser to penetrate the capping layer and adjust the frequency quality of the detection end adjustment structure, the coupling structure quality Δm2 is reduced.

[0031] S706. Test the gyroscope drive resonant frequency fd and the detection resonant frequency fs of the MEMS ring gyroscope, and calculate the frequency difference Δf = fd - fs. If the recalculated Δf meets the set frequency difference requirement, the adjustment of the MEMS ring gyroscope is ended; otherwise, return to step S705.

[0032] Furthermore, in steps S1-S5, the microstructures of multiple MEMS ring gyroscopes are fabricated on the same wafer using a mass production process, and all MEMS ring gyroscopes on the wafer surface are uniformly packaged.

[0033] In step S6, the wafer-level vacuum-packaged wafer is tested;

[0034] In step 706, after the adjustment of the MEMS ring gyroscope is completed, proceed to step S707;

[0035] S707. Proceed to the next MEMS ring gyroscope adjustment, repeating steps S701-S706 until all MEMS ring gyroscopes on the entire wafer have been adjusted, and the quality adjustment is completed.

[0036] The beneficial effects of this invention are:

[0037] (1) This invention can achieve full symmetry of the mechanical structure by adjusting the mass of the structure after the structure is processed, thereby changing the structure frequency, effectively suppressing coupling errors, achieving modal matching, improving the Q value and mechanical sensitivity of the gyroscope, reducing noise, improving the signal-to-noise ratio of the gyroscope, and improving the zero-bias stability of the gyroscope. Compared with the electrostatic negative stiffness coefficient adjustment method, it directly changes the inherent frequency of the structure itself, and can fundamentally solve the problems of orthogonal coupling error and frequency fragmentation of the structure, and reduce the complexity of the subsequent measurement and control circuit. By adjusting the mechanical structure, coupling error adjustment and modal matching are achieved, reducing the measurement and control voltage requirements of the back-end ASIC circuit, reducing the complexity of the measurement and control circuit and the requirements of the chip fabrication process, improving the reliability of the circuit, and helping to improve the reliability and environmental adaptability of the gyroscope.

[0038] (2) The substrate layer, MEMS resonant device layer, and cap layer of the present invention form a sandwich structure. This sandwich structure is advantageous for processing the microstructure of multiple MEMS ring gyroscopes on the same wafer using mass production processes, and is beneficial for achieving unified wafer-level vacuum packaging of all MEMS ring gyroscopes on the wafer. After wafer-level vacuum packaging, the structural quality can be adjusted by using a laser through the transparent cap layer, enabling wafer-level testing and wafer-level adjustment to still be performed after wafer-level vacuum packaging. This solves the problem that the structural symmetry of MEMS ring gyroscopes cannot be changed after traditional wafer-level packaging. The process is simple, easy to implement, and highly efficient, which is conducive to achieving low-cost mass production of MEMS ring gyroscopes.

[0039] (3) The process tolerance of the present invention is greatly improved, the complexity of the process is reduced, the repeatability of the process is improved, and the performance accuracy and process robustness of the MEMS ring gyroscope can be improved after adjustment. Attached Figure Description

[0040] To make the objectives, technical solutions, and beneficial effects of this invention clearer, the following figures are provided for illustration:

[0041] Figure 1This is a schematic diagram of the adjustable MEMS ring gyroscope of the present invention during adjustment (to clearly show the structure, the cut-off position is the location of the detection end frequency quality adjustment structure and the coupling quality adjustment structure, and the cut-off direction is...). Figure 2 (direction indicated by the middle arrow)

[0042] Figure 2 This is a top view of the ring harmonic oscillator of the present invention;

[0043] Figure 3 The structure obtained in step S1 of the manufacturing method of the adjustable MEMS ring vibrating gyroscope of the present invention;

[0044] Figure 4 The structure obtained in step S2 of the manufacturing method of the MEMS ring vibrating gyroscope of the present invention;

[0045] Figure 5 The structure obtained in step S3 of the manufacturing method of the adjustable MEMS ring vibrating gyroscope of the present invention;

[0046] Figure 6 The structure obtained in step S4 of the manufacturing method of the adjustable MEMS ring vibrating gyroscope of the present invention;

[0047] Figure 7 The structure obtained in step S5 of the manufacturing method of the adjustable MEMS ring vibrating gyroscope of the present invention;

[0048] Figure 8 This is a schematic diagram illustrating the adjustment process in step S7 of the manufacturing method of the adjustable MEMS ring vibrating gyroscope of the present invention.

[0049] Figure 9 This is a flowchart illustrating the manufacturing method of the adjustable MEMS ring vibrating gyroscope of the present invention.

[0050] Figure 10 This is a flowchart of step S7 in the manufacturing method of the adjustable MEMS ring vibrating gyroscope of the present invention;

[0051] Figure 11 This is a flowchart of step S7 of the manufacturing method of the adjustable MEMS ring vibrating gyroscope of the present invention.

[0052] Figure 12 The simulation graph shows the variation of the mechanical sensitivity of the gyroscope with frequency difference.

[0053] Figure 13 This is a simulation graph showing the change in resonant frequency of a gyroscope as a function of mass.

[0054] Figure 14 This is a simulation diagram showing the change in the spindle deflection angle of a gyroscope driven by mass.

[0055] The following labels are shown in the attached diagram:

[0056] 1-Base layer, 11-First support stage, 12-Second support stage, 13-Third support stage, 14-Fourth support stage, 15-First lower groove, 16-Second lower groove, 17-Third upper groove, 18-Silicon wafer layer, 19-Insulating layer;

[0057] 2-MEMS resonant device layer, 21-ring resonator, 211-vibrating ring, 212-support anchor point, 213-elastic support beam, 214-detection end frequency quality adjustment structure, 215-coupling quality adjustment structure, 22-fixed electrode assembly, 221-inner fixed electrode, 222-outer fixed electrode, 23-enclosure.

[0058] 3-Cap layer, 31-Through hole, 32-First upper groove, 33-Second upper groove, 34-Third upper groove, 35-Film getter;

[0059] 4-Electrode layer;

[0060] 5-laser, 51-laser. Detailed Implementation

[0061] First, the working principle of this invention will be explained here:

[0062] A MEMS ring gyroscope consists of a two-degree-of-freedom mass-spring-damped system: one for the driving mode and the other for the sensing mode, with its mechanical sensitivity... Among them, mechanical sensitivity S mech The output angular velocity Ω represents the gyroscope's response to the input angular velocity and is a core indicator of gyroscope performance. y0 represents the output displacement amplitude, the maximum vibration displacement in the detection direction (Y-axis), caused by Coriolis force. y0 is related to the input angular velocity Ω. z Proportional; Ω z The rotational angular velocity to be measured is the target signal that the gyroscope needs to detect; n is the mode order of the gyroscope's operation; MEMS ring gyroscopes typically operate in n=2 or n=3 degenerate modes; A g ω is the angle gain coefficient; x0 is the driving displacement amplitude, which is the vibration amplitude in the driving direction (X-axis); d Let ω be the frequency of the electrostatic driving force. d Typically related to the gyroscope drive mode frequency ω x Same; ω y To detect modal frequencies.

[0063] When the gyroscope is in modal matching, i.e., ω d =ω y The gyroscope reaches its maximum mechanical sensitivity. The resonant frequency of the gyroscope's operating mode. The resonant frequency ω depends on the structural stiffness k and mass m. Changing either the stiffness or the mass alters the resonant frequency. The electrostatic negative stiffness coefficient... Where ε is the dielectric constant, A is the effective area of ​​the electrode, ΔV is the voltage difference between the electrodes, and d is the electrode spacing. Therefore, the electrostatic negative stiffness coefficient k e The frequency is proportional to the voltage difference across the structure. Traditional methods of structural frequency tuning involve adjusting the voltage across the terminals to change the overall stiffness of the structure, thereby altering its natural frequency. However, this method requires a large voltage difference for control when the initial frequency drop is significant, potentially exceeding the voltage limit of the ASIC circuit. Furthermore, during gyroscope operation, the voltage difference must be precisely controlled in real-time to avoid errors. For example, if the initial frequency drop is 10Hz, tuning to the 1MHz range is required, achieving a dynamic range of 10Hz. 4 The sheer scale of these systems places extremely high demands on the control system, making it difficult to guarantee its robustness.

[0064] Mechanical coupling error coefficient of MEMS ring gyroscope Δω represents the frequency difference between the driving and sensing modes, and θ represents the deflection angle. Reducing the deflection angle can effectively improve mechanical coupling error. Traditional mechanical coupling error correction methods also utilize electrostatic negative stiffness coefficient control. For a MEMS ring gyroscope with n=2, this is achieved by adjusting the voltage across the terminals at the midpoint of the angle between the driving and sensing modes (22.5°). This changes the axial stiffness at that position, thus adjusting the deflection angle θ of the gyroscope's rigid principal axis, thereby reducing coupling error. This method faces the same problem as frequency electrostatic correction: when the coupling error is large, a large adjustment voltage is required, potentially exceeding the voltage limit of the ASIC circuit. Furthermore, during gyroscope operation, the voltage difference must be precisely controlled in real time. If the mechanical coupling error is not properly controlled, it will result in a large gyroscope zero-bias error.

[0065] The mechanical adjustment of coupling error and structural frequency proposed in this embodiment involves designing a detection end frequency quality adjustment structure 214 and a coupling quality adjustment structure 215 in the MEMS ring gyroscope. The MEMS ring gyroscope is fabricated using sandwich MEMS technology and wafer-level vacuum packaging, with transparent glass as the cap layer 3. After achieving wafer-level vacuum packaging of the gyroscope chip, the mechanical coupling error signal, driving mode frequency, and detection mode frequency of the gyroscope are measured in real time. Through the transparent cap layer 3, a laser 51 is used to locally adjust the quality adjustment structure, reducing the structural mass, changing the rigid spindle deflection angle, increasing the operating frequency of the detection mode, reducing the coupling error, and achieving a state that matches the driving mode frequency. The structure and manufacturing scheme proposed in this invention enable mechanical coupling error and frequency adjustment of MEMS ring gyroscopes after vacuum packaging, reducing the impact of process errors and allowing the chip to achieve modal matching in its original mechanical structure. This also improves structural symmetry, effectively suppresses orthogonal coupling errors and anchor point losses, increases the Q value of the gyroscope chip, further enhances the gyroscope's mechanical sensitivity, reduces mechanical thermal noise, improves the overall signal-to-noise ratio, effectively suppresses coupling errors, and enhances the gyroscope's zero-bias stability. By achieving gyroscope coupling error suppression and modal matching through mechanical adjustment, complex control circuits are not required for backend signal processing, enhancing system robustness. Simultaneously, it reduces the high-voltage output requirements of the ASIC circuit, facilitating low-power, small-size, and low-cost mass production and improving product cost-effectiveness.

[0066] The technical solution of the present invention will be described in detail below with reference to the accompanying drawings and embodiments. In the following text, "radial outward" refers to the direction in which the ring resonator 21 gradually moves away from its center along the radial direction, "radial inward" refers to the direction in which the ring resonator 21 gradually moves closer to its center along the radial direction, "circumferential" refers to the direction around the center of the ring resonator 21, and "axial" refers to the direction passing through the center of the ring resonator 21 and perpendicular to the ring resonator 21.

[0067] Example 1:

[0068] like Figure 1 and Figure 2 As shown, an adjustable MEMS ring gyroscope in this embodiment includes a base layer 1, a MEMS resonant device layer 2, and a cap layer 3.

[0069] The MEMS resonant device layer 2 includes a ring resonator 21 and a fixed electrode assembly 22. The ring resonator 21 includes a vibrating ring 211 and a support structure disposed within the vibrating ring 211. The support structure includes a support anchor point 212 and multiple elastic support beams 213. The two ends of the multiple elastic support beams 213 are respectively connected to the vibrating ring 211 and the support anchor point 212. The vibrating ring 211 is suspended between the base layer 1 and the cap layer 3. The support anchor point 212 and the upper and lower sides of the fixed electrode assembly 22 are respectively fixedly connected to the cap layer 3 and the base layer 1. Multiple detection end frequency quality adjustment structures 214 and multiple coupling quality adjustment structures 215 are arranged circumferentially on the outer wall of the vibrating ring 211.

[0070] The cap layer 3 is provided with through holes 31 at the positions corresponding to the support anchor point 212 and the fixed electrode assembly 22, and the electrode layer 4 is provided in the through holes 31. The cap layer 3 is transparent at the positions corresponding to the detection end frequency quality adjustment structure 214 and the coupling quality adjustment structure 215.

[0071] The electrode layer 4 on the cap layer 3 is used to transmit electrical signals. The electrode layer 4 is connected to the support anchor point 212 and the individual inner fixed electrodes 221 and outer fixed electrodes 222 of the fixed electrode assembly 22 through the through hole 31. The cap layer 3 is made of transparent glass (e.g., borosilicate glass). The cap layer 3 is transparent in the areas where the electrode layer 4 is not set. The area of ​​the transparent structure is not limited and can completely cover the entire vibration ring 211. However, it is necessary to ensure that the transparent structure covers the detection end frequency quality adjustment structure 214 and the coupling quality adjustment structure 215. The laser 51 can perform quality adjustment on the detection end frequency quality adjustment structure 214 and the coupling quality adjustment structure 215 through the transparent material, which can reduce the mass of the quality adjustment structure.

[0072] After the structure is fabricated, the mass of the structure is adjusted to change its frequency, achieving full symmetry of the mechanical structure. This effectively suppresses coupling errors, achieves modal matching, improves the gyroscope's Q value and mechanical sensitivity, reduces noise, enhances the signal-to-noise ratio, and improves zero-bias stability. Compared to adjusting the electrostatic negative stiffness coefficient, this method directly changes the structure's inherent frequency, fundamentally solving the problems of orthogonal coupling errors and frequency fragmentation, and reducing the complexity of subsequent measurement and control circuits. By adjusting the mechanical structure to achieve coupling error regulation and modal matching, the measurement and control voltage requirements of the backend ASIC circuit are reduced, as are the complexity of the measurement and control circuit and the requirements for the fabrication process. This improves circuit reliability and enhances the gyroscope's reliability and environmental adaptability.

[0073] The substrate layer 1, the MEMS resonant device layer 2, and the cap layer 3 form a sandwich-like structure. This sandwich-like structure facilitates the fabrication of multiple MEMS ring gyroscopes on the same wafer using mass production processes, and enables unified wafer-level vacuum packaging of all MEMS ring gyroscopes on the wafer. After wafer-level vacuum packaging, a laser 51 can be used to adjust the structural quality through the transparent cap layer 3, allowing for wafer-level testing and adjustment even after wafer-level vacuum packaging. This solves the problem that the structural symmetry of MEMS ring gyroscopes cannot be changed after traditional wafer-level packaging. The process is simple, easy to implement, and highly efficient, which is conducive to the low-cost mass production of MEMS ring gyroscopes.

[0074] In this embodiment, a plurality of detection end frequency quality adjustment structures 214 are equally spaced along the circumference on the outer wall of the vibrating ring 211, and each detection end frequency quality adjustment structure 214 has a coupling quality adjustment structure 215 disposed on different sides of the circumference. In this embodiment, there are four detection end frequency quality adjustment structures 214, and the included angle between two adjacent detection end frequency quality adjustment structures 214 is 90°; there are eight coupling quality adjustment structures 215, and each detection end frequency quality adjustment structure 214 has a coupling quality adjustment structure 215 disposed at a 22.5° interval on different sides of the circumference.

[0075] Specifically, taking one of the detection end frequency quality adjustment structures 214 at a position of 0° in the circumferential direction of the vibration ring 211 as an example, the four detection end frequency quality adjustment structures 214 are located at 0°, 90°, 180°, and 270° of the vibration ring 211, respectively, and the eight coupling quality adjustment structures 215 are located at 22.5°, 67.5°, 112.5°, 157.5°, 202.5°, 247.5°, 292.5°, and 337.5° of the vibration ring 211, respectively.

[0076] In this embodiment, the fixed electrode assembly 22 includes multiple inner fixed electrodes 221 independently disposed within the vibrating ring 211 and multiple outer fixed electrodes 222 independently disposed outside the vibrating ring 211. The multiple inner fixed electrodes 221 and multiple outer fixed electrodes 222 are distributed on the inner and outer sides of the vibrating ring 211 to realize the functions of driving, detecting, and orthogonal control of the gyroscope.

[0077] In this embodiment, the MEMS resonant device layer 2 further includes a closed portion 23 disposed radially outside the external fixed electrode 222. The base layer 1 is provided with a first support platform 11, a second support platform 12, a third support platform 13 and a fourth support platform 14. The first support platform 11 is connected to the support anchor point 212, the second support platform 12 is connected to the internal fixed electrode 221, the third support platform 13 is connected to the external fixed electrode 222, and the fourth support platform 14 is connected to the closed portion 23.

[0078] The first support stage 11, the second support stage 12, the third support stage 13 and the fourth support stage 14 of the substrate layer 1 are used to bond to various parts of the MEMS resonant device layer 2 and can provide support for the MEMS resonant device layer 2.

[0079] In this embodiment, a second lower groove 16 is provided between the base layer 1 and the second support platform 12 and the third support platform 13, and a second upper groove 33 is provided between the cap layer 3 and the second lower groove 16. The second lower groove 16 and the second upper groove 33 are arranged facing each other, and a cavity is formed between the second lower groove 16 and the second upper groove 33 to provide a space for the vibration ring 211, the detection end frequency quality adjustment structure 214 and the coupling quality adjustment structure 215.

[0080] The second lower groove 16 and the second upper groove 33 are used to suspend the vibration ring 211, the detection end frequency quality adjustment structure 214 and the coupling quality adjustment structure 215, ensuring that the vibration ring 211, the detection end frequency quality adjustment structure 214 and the coupling quality adjustment structure 215 can move.

[0081] The base layer 1 has a first lower groove 15 between the first support platform 11 and the second support platform 12. The cap layer 3 has a first upper groove 32 at the position corresponding to the first lower groove 15. The first lower groove 15 and the first upper groove 32 are arranged facing each other. The base layer 1 has a third lower groove 17 between the third support platform 13 and the fourth support platform 14. The cap layer 3 has a third upper groove 34 at the position corresponding to the third lower groove 17. The third lower groove 17 and the third upper groove 34 are arranged facing each other. A thin film getter 35 is disposed in the third upper groove 34.

[0082] The first lower groove 15, the second lower groove 16, and the third lower groove 17 prevent damage to the substrate layer 1 during etching of the MEMS resonant device layer 2. Thin-film getter 35 is used to achieve wafer-level vacuum packaging, providing a low-damping operating atmosphere for the gyroscope and improving its Q-value.

[0083] In this embodiment, the substrate layer 1 includes a silicon wafer layer 18 and an insulating layer 19 disposed on the upper outer surface of the silicon wafer layer 18.

[0084] Example 2:

[0085] like Figures 1-14 As shown, this embodiment illustrates a method for manufacturing an adjustable MEMS ring gyroscope, used to manufacture the adjustable MEMS ring gyroscope in Embodiment 1, comprising the following steps:

[0086] S1, such as Figure 3 and Figure 9 As shown, a single crystal silicon with a thickness of 300μm to 725μm is selected as the first layer structure. The first under-groove 15, the second under-groove 16 and the third under-groove 17 are etched on it with an etching depth of 10μm to 80μm. An insulating layer 19 with a thickness of 0.5μm to 3μm is grown on its surface through an insulating layer 19 generation process (e.g., thermal oxidation process) to form a double-layer structure of silicon wafer layer 18 and insulating layer 19, thus completing the fabrication of the substrate layer 1.

[0087] S2, such as Figure 4 and Figure 9 As shown, single-crystal silicon with a low resistivity of 0.001Ω*cm~0.1Ω*cm is selected as the second layer structure. Its back side is bonded to the substrate layer 1 by silicon-silicon dioxide bonding. The device layer is thinned to 30~150μm, and then its front side is subjected to deep silicon etching. The ring resonator 21, fixed electrode assembly 22, sealing part 23, multiple detection end frequency quality adjustment structure 214 and multiple coupling quality adjustment structure 215 are fabricated by etching. Since the substrate layer 1 has a second lower groove 16, the vibrating ring 211 is suspended, thus completing the fabrication of MEMS resonant device layer 2.

[0088] S3, such as Figure 5 and Figure 9 As shown, borosilicate glass with a thickness of 200μm to 500μm is selected as the third layer structure, and through holes 31 of a certain diameter are etched in local positions. The back side is processed by etching a first upper groove 32, a second upper groove 33, and a third upper groove 34 with a depth of 10μm to 80μm, and a thin film getter 35 is deposited in the first upper groove 32 and the third upper groove 34.

[0089] S4, such as Figure 6 and Figure 9 As shown, the component obtained in step S3 is anodicly bonded to the MEMS resonant device layer 2 to form a hermetically sealed vacuum package, and the thin film getter 35 is activated to complete the fabrication of the cap layer 3.

[0090] S5, such as Figure 7 and Figure 9As shown, a metal film, such as Al or Au, with a thickness of 1 μm to 3 μm is deposited on the surface of the cap layer 3 (including inside the through hole 31). Photolithography and etching processes are performed to form the electrode layer 4. The metal film at the positions of the cap layer 3 corresponding to the vibration ring 211, the detection end frequency quality adjustment structure 214, and the coupling quality adjustment structure 215 is removed, so that only borosilicate glass forms a transparent structure at these positions, resulting in an adjustable MEMS ring vibration gyroscope.

[0091] Example 3:

[0092] The technical solution of this embodiment is an improvement on the basis of embodiment two. After obtaining the adjustable MEMS ring gyroscope, it is tested and its quality is adjusted. That is, steps S6 and S7 are performed after step S5 in embodiment two.

[0093] S6. Test the gyroscope coupling error signal, gyroscope drive resonant frequency, and detection resonant frequency of the MEMS ring vibrating gyroscope. The gyroscope coupling error signal Vm is typically equivalent to 1–10° / s, the gyroscope drive resonant frequency fd and the detection resonant frequency fs are typically 5kHz–20kHz, and the frequency difference Δf is typically 1Hz–10Hz. If the test is successful, the process ends; if the test fails, proceed to step S7.

[0094] S7, such as Figure 8 , Figure 10 and Figure 11 As shown, quality adjustment; specifically including:

[0095] S701. Test the gyroscope coupling error signal Vm of the MEMS ring vibrating gyroscope, compare it with the given error signal reference value V0, and calculate ΔV=Vm-V0;

[0096] S702, Laser 51 is emitted by laser 5 through cap layer 3 and coupling mass adjustment structure 215 is adjusted to reduce its coupling mass Δm1; Δm1 can be a preset value, and different sizes of Δm1 are preset according to different specifications and models of MEMS ring vibration gyroscope.

[0097] S703. Retest the gyroscope coupling error signal Vm of the MEMS ring vibrating gyroscope, compare it with the given error signal reference value V0, and recalculate ΔV=Vm-V0; if the recalculated ΔV meets the set error signal requirement, proceed to step S704; otherwise, return to step S702.

[0098] S704. Test the gyroscope drive resonant frequency fd and the detection resonant frequency fs of the MEMS ring vibrating gyroscope, and calculate the frequency difference Δf = fd - fs;

[0099] S705, the laser 51 emitted by the laser 5 passes through the cap layer 3 and adjusts the frequency quality adjustment structure 214 of the detection end to reduce its coupling structure quality Δm2; Δm2 can be a preset value, and different sizes of Δm2 are preset according to different specifications and models of MEMS ring vibration gyroscopes.

[0100] S706. Test the gyroscope drive resonant frequency fd and the detection resonant frequency fs of the MEMS ring gyroscope, and calculate the frequency difference Δf = fd - fs. If the recalculated Δf meets the set frequency difference requirement, the adjustment of the MEMS ring gyroscope is ended; otherwise, return to step S705.

[0101] Example 4:

[0102] The technical solution in this embodiment is an improvement on Embodiment 3. Steps S1-S5 employ a mass production process to fabricate the microstructures of multiple MEMS ring gyroscopes on the same wafer, and uniformly package all MEMS ring gyroscopes on the wafer surface. It is worth noting that the mass production process refers to the fabrication of multiple substrate layers 1 on the same wafer through step S1, followed by the fabrication of multiple MEMS resonant device layers 2 through step S2. Similarly, steps S3, S4, and S5 are used to fabricate the microstructures of multiple MEMS ring gyroscopes on the same wafer, and uniformly package all MEMS ring gyroscopes on the wafer using wafer-level vacuum packaging.

[0103] Since steps S1-S5 employ mass production processes, steps S6 and S7 have been correspondingly modified to wafer-level testing and wafer-level trimming.

[0104] In step S6, the wafer-level vacuum-packaged wafer is tested;

[0105] In step 706, after the adjustment of the MEMS ring gyroscope is completed, proceed to step S707;

[0106] S707. Proceed to the next MEMS ring gyroscope adjustment, repeating steps S701-S706 until all MEMS ring gyroscopes on the entire wafer have been adjusted, and the quality adjustment is completed.

[0107] The substrate layer 1, MEMS resonant device layer 2, and cap layer 3 form a sandwich-like structure. This sandwich-like structure facilitates the fabrication of multiple MEMS ring gyroscopes on the same wafer using mass production processes, and enables unified wafer-level vacuum packaging of all MEMS ring gyroscopes on the wafer. After wafer-level vacuum packaging, a laser 51 can be used to adjust the structural quality through the transparent cap layer 3, allowing for wafer-level testing and adjustment even after vacuum packaging. This solves the problem that traditional wafer-level packaging cannot alter the structural symmetry of MEMS ring gyroscopes. The process is simple, easy to implement, and highly efficient, facilitating low-cost mass production of MEMS ring gyroscopes. Furthermore, the process tolerance is significantly improved, reducing process complexity and improving process repeatability. After adjustment, the performance accuracy and process robustness of the MEMS ring gyroscope can also be improved.

[0108] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention, and all such modifications or substitutions should be covered within the scope of the claims of the present invention.

Claims

1. An adjustable MEMS ring gyroscope, characterized in that: It includes a substrate layer, a MEMS resonant device layer, and a capping layer; The MEMS resonant device layer includes a ring resonator and a fixed electrode assembly. The ring resonator includes a vibrating ring and a support structure disposed within the vibrating ring. The support structure includes a support anchor point and multiple elastic support beams. The two ends of the multiple elastic support beams are respectively connected to the vibrating ring and the support anchor point. The vibrating ring is suspended between the base layer and the cap layer. The support anchor point and the upper and lower sides of the fixed electrode assembly are respectively fixedly connected to the cap layer and the base layer. Multiple detection end frequency quality adjustment structures and multiple coupling quality adjustment structures are arranged circumferentially at intervals on the outer wall of the vibrating ring. The cap layer is provided with through holes corresponding to the support anchor point and the fixed electrode assembly, and the electrode layer is provided in the through holes. The cap layer is transparent in the position corresponding to the detection end frequency quality adjustment structure and the coupling quality adjustment structure. Multiple detection end frequency quality adjustment structures are equally spaced along the circumference on the outer wall of the vibrating ring, and each detection end frequency quality adjustment structure has a coupling quality adjustment structure on different sides of the circumference. The number of detection end frequency quality adjustment structures is four, and the included angle between two adjacent detection end frequency quality adjustment structures is 90°; the number of coupling quality adjustment structures is eight, and each detection end frequency quality adjustment structure is provided with one coupling quality adjustment structure at a 22.5° interval on different sides in the circumferential direction.

2. The adjustable MEMS ring gyroscope according to claim 1, characterized in that: The fixed electrode assembly includes multiple inner fixed electrodes independently disposed within the vibrating ring and multiple outer fixed electrodes independently disposed outside the vibrating ring.

3. The adjustable MEMS ring gyroscope according to claim 2, characterized in that: The MEMS resonant device layer further includes a closed portion disposed radially outside the external fixed electrode. A first support platform, a second support platform, a third support platform, and a fourth support platform are disposed on the substrate layer. The first support platform is connected to the support anchor point, the second support platform is connected to the internal fixed electrode, the third support platform is connected to the external fixed electrode, and the fourth support platform is connected to the closed portion.

4. The adjustable MEMS ring gyroscope according to claim 3, characterized in that: The base layer is provided with a second lower groove between the second support platform and the third support platform, and the cap layer is provided with a second upper groove at the position of the second lower groove. The second lower groove and the second upper groove are arranged facing each other, and a cavity is formed between the second lower groove and the second upper groove to provide a space for the vibration ring, the detection end frequency quality adjustment structure and the coupling quality adjustment structure. The base layer is provided with a first lower groove between the first support platform and the second support platform, and the cap layer is provided with a first upper groove at the position of the first lower groove, with the first lower groove and the first upper groove facing each other. The base layer has a third lower groove between the third support platform and the fourth support platform, and the cap layer has a third upper groove at the position of the third lower groove. The third lower groove and the third upper groove are arranged facing each other, and a thin film getter is disposed in the third upper groove.

5. The adjustable MEMS ring gyroscope according to claim 4, characterized in that: The substrate layer includes a silicon wafer layer and an insulating layer disposed on the upper outer surface of the silicon wafer layer.

6. A method for manufacturing an adjustable MEMS ring vibrating gyroscope, characterized in that, The method for manufacturing the adjustable MEMS ring vibrating gyroscope as described in claim 5 includes the following steps: S1. Select monocrystalline silicon as the first layer structure, etch the first, second and third under-grooves on it, and make its surface insulated by the insulating layer generation process to form a double-layer structure of silicon wafer layer and insulating layer, and complete the manufacturing of the substrate layer. S2. Single-crystal silicon is selected as the second layer structure and bonded to the substrate layer. The ring resonator, fixed electrode assembly, sealing part, multiple detection end frequency quality adjustment structure and multiple coupling quality adjustment structure are etched to complete the fabrication of the MEMS resonant device layer. S3. Borosilicate glass is selected as the third layer structure. Through holes, first upper groove, second upper groove and third upper groove are etched out, and a thin film getter is deposited in the first upper groove and third upper groove. S4. The component obtained in step S3 is anodicly bonded to the MEMS resonant device layer to form a hermetically sealed vacuum package, and the thin film getter is activated to complete the fabrication of the cap layer. S5. Deposit a metal film on the surface of the cap layer, perform photolithography and etching processes to form an electrode layer, and make the positions of the cap layer corresponding to the vibration ring, the detection end frequency quality adjustment structure and the coupling quality adjustment structure transparent to obtain an adjustable MEMS ring vibration gyroscope.

7. The method for manufacturing the adjustable MEMS ring vibrating gyroscope according to claim 6, characterized in that: The manufacturing method further includes: S6. Test the gyroscope coupling error signal, gyroscope drive resonant frequency, and detection resonant frequency of the MEMS ring vibrating gyroscope. If the test is qualified, the process ends; if the test is unqualified, proceed to step S7. S7. Quality adjustment; specifically including: S701. Test the gyroscope coupling error signal Vm of the MEMS ring vibrating gyroscope, compare it with the given error signal reference value V0, and calculate ΔV=Vm-V0; S702. By using laser to penetrate the capping layer and adjust the coupling mass of the structure, the coupling mass Δm1 is reduced. S703. Retest the gyroscope coupling error signal Vm of the MEMS ring vibrating gyroscope, compare it with the given error signal reference value V0, and recalculate ΔV=Vm-V0; if the recalculated ΔV meets the set error signal requirement, proceed to step S704; otherwise, return to step S702. S704. Test the gyroscope drive resonant frequency fd and the detection resonant frequency fs of the MEMS ring vibrating gyroscope, and calculate the frequency difference Δf = fd - fs; S705. By using laser to penetrate the capping layer and adjust the frequency quality of the detection end adjustment structure, the coupling structure quality Δm2 is reduced. S706. Test the gyroscope drive resonant frequency fd and the detection resonant frequency fs of the MEMS ring gyroscope, and calculate the frequency difference Δf = fd - fs. If the recalculated Δf meets the set frequency difference requirement, the adjustment of the MEMS ring gyroscope is ended; otherwise, return to step S705.

8. The method for manufacturing the adjustable MEMS ring vibrating gyroscope according to claim 7, characterized in that: In steps S1-S5, the microstructures of multiple MEMS ring gyroscopes are fabricated on the same wafer using a mass production process, and all MEMS ring gyroscopes on the wafer are uniformly vacuum packaged at the wafer level. In step S6, the MEMS ring gyroscope on the wafer that has been vacuum-packaged at the wafer level is tested; In step S706, after the adjustment of the MEMS ring gyroscope is completed, proceed to step S707; S707. Proceed to the next MEMS ring gyroscope adjustment, repeating steps S701-S706 until all MEMS ring gyroscopes on the entire wafer have been adjusted, and the quality adjustment is completed.

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