Micro-optical accelerometer with force balance feedback

Abstract

The application discloses a micro-optical accelerometer with force balance feedback, which is composed of a MEMS sensitive unit, a grating unit, a detection unit and a plurality of packaging ceramic substrates, and is integrally packaged in a metal tube shell through wire bonding. The MEMS sensitive unit is composed of a plurality of spring-mass structures with a mirror and a lower metal electrode. The grating unit is composed of a plurality of triangularly distributed gratings with an upper metal electrode. The detection unit is composed of three triangularly distributed light transceiver assemblies. One light transceiver assembly contains a VCSEL laser and two PD detector chips. The plurality of packaging ceramic substrates assemble the units together according to the required interval, and the upper surface is distributed with metal pads to realize electrical connection with the outside. The application integrates the electrostatic force feedback function and a plurality of light transceiver assemblies. The micro-optical accelerometer can work in multiple modes, effectively suppresses cross-axis crosstalk, and realizes ultra-high precision acceleration measurement.

Description

Technical Field

[0001] This invention belongs to the technical field of micro-opto-electro-mechanical systems and accelerometers (micro-inertial measurement), and more specifically, relates to a micro-optical accelerometer that can sense out-of-plane acceleration, support force balance feedback, and optical displacement detection. Background Technology

[0002] Due to limitations imposed by traditional electrical measurement methods, conventional MEMS such as piezoresistive, capacitive, and resonant MEMS have encountered bottlenecks in terms of measurement sensitivity and noise, failing to meet the demands of applications such as high-precision inertial navigation, seismic monitoring, and deep space and deep-sea exploration. In recent years, optical MEMS accelerometers based on optical detection and MEMS technology, namely micro-optical accelerometers, have gradually come into focus. MEMS technology provides a solid technological foundation for the realization of micro-optical accelerometers. Furthermore, optical detection schemes employ optical detection methods such as light intensity, frequency, phase, and near-field effects to detect the displacement of the sensitive unit, offering superior displacement detection resolution compared to traditional electrical detection methods. Micro-optical accelerometers possess a series of advantages, including high precision and resistance to electromagnetic interference. With further development in photonic integrated design and processes, they will have enormous application potential in the field of high-precision inertial measurement.

[0003] In recent years, research institutions both domestically and internationally have begun to conduct some research on micro-optical accelerometers. In 2008, NA Hall et al. from Sandia National Laboratories in the United States proposed a novel optical micro-accelerometer structure, which uses a VCSEL laser source to excite a grating connected to a mass block. The intensity of the reflected light from the grating is used to measure the grating displacement and the magnitude of acceleration caused by acceleration, with a theoretical acceleration detection accuracy of 43.7 ng / Hz. In 2017, Lu Qianbo et al. from Zhejiang University proposed a micro-optical accelerometer based on a grating interferometer cavity and optimized the sensing structure, achieving a noise floor of 185.8 ng / Hz. In 2019, Gao Shan et al. from Beijing University of Aeronautics and Astronautics achieved low optical noise floor and zero-bias stability of 3.1 μg based on a Gaussian beam; however, this scheme ultimately failed to achieve practical accelerometer integration. As the requirements for the performance of micromechanical accelerometers continue to increase, the demand for high-precision micro accelerometers with inertial navigation grade, i.e. better than 1 μg, is becoming more and more urgent. However, existing micro-optical accelerometers have low detection sensitivity, poor process integration, and do not have closed-loop detection function, which cannot meet the requirements. Summary of the Invention

[0004] In response to the above-mentioned defects or improvement needs of existing technologies, this invention proposes a micro-optical accelerometer with force balance feedback, which solves the problems of poor detection sensitivity, cross-axis suppression capability and poor process integration in existing technologies.

[0005] To achieve the above objectives, the present invention provides a micro-optical accelerometer with force balance feedback, which consists of a MEMS sensing unit, a grating unit, a detection unit and multiple ceramic substrates for packaging, and is encapsulated in a metal tube by wire bonding.

[0006] The MEMS sensing unit consists of a reflector, a lower metal electrode, and a symmetrically distributed spring-mass block structure.

[0007] The grating unit consists of an upper metal electrode, multiple symmetrically distributed gratings, and a grating support frame;

[0008] The detection unit consists of multiple sets of optical transceiver components arranged in a preset shape, wherein the distribution shape of the multiple sets of gratings is consistent with the distribution shape of the multiple sets of optical transceiver components.

[0009] The ceramic substrate for packaging consists of a lower ceramic substrate with metal pads, an upper ceramic substrate with metal pads, and a hollow thick ceramic substrate.

[0010] The MEMS sensing unit and the grating unit are bonded together as a whole to the central region of the lower ceramic substrate with metal pads after gold-gold bonding; the detection unit is bonded to the central region of the upper ceramic substrate with metal pads; the MEMS sensing unit and the grating unit are separated from the detection unit, and the spacing is determined by the hollow thick ceramic substrate.

[0011] In some alternative implementations, the spring-mass structure is a series of cantilever beam-mass structures symmetrically distributed along the circumference, enabling the spring-mass structure to perform out-of-plane motion.

[0012] Both the reflector and the lower metal electrode are located on the upper surface of the spring-mass structure and are patterned and gold-plated from the upper surface portion of the MEMS sensing unit. The reflector is located on the mass block at the center of the upper surface of the spring-mass structure, and the lower metal electrode is located on other patterned portions of the upper surface of the spring-mass structure. The lower metal electrode connects the reflector to the outer frame via a spring.

[0013] In some optional implementations, the upper metal electrode is patterned and gold-plated on the lower surface of the grating unit, and is electrically connected to the upper surface of the grating unit through a TSV process. The symmetrically distributed gratings are located in the central region of the grating unit and together with the reflector on the upper surface of the MEMS sensing unit, they form a grating interference cavity. The length of the interference cavity can change with the movement of the spring-mass structure. The grating support frame is the surrounding area of ​​the grating unit, which serves to support the grating and realize the bonding process connection with the MEMS sensing unit.

[0014] In some optional implementations, each set of optical transceiver components consists of a laser chip and two detector chips, and the position of each set of optical transceiver components corresponds one-to-one with the position of the gratings that are symmetrically distributed below. The laser emitted downward by the laser chip passes through the grating interference cavity and is symmetrically returned to the target surface of the two detector chips in the same set, thereby realizing the displacement detection of the cavity length of the grating interference cavity.

[0015] In some alternative implementations, the lower metal electrode located in the MEMS sensing unit is electrically isolated from the upper metal electrode located in the grating unit, and is integrally packaged in a metal housing by wire bonding to realize the force balance feedback loop of the micro-optical accelerometer.

[0016] In some alternative implementations, the gratings symmetrically distributed in the central region of the grating unit are linear gratings uniformly distributed along the circumference according to a preset shape. The gratings are made by etching uniformly spaced linear grooves on a silicon wafer to achieve the function of splitting and combining laser light.

[0017] In some optional implementations, multiple sets of detectors are formed by uniformly distributed gratings in a preset shape and corresponding optical transceiver components to jointly detect the motion of the mirror located above the MEMS sensing unit, thereby improving the cross-axis suppression ratio of the accelerometer. In this case, a set of detectors consists of a grating, a laser chip, and two detector chips, and the multiple sets of detectors are distributed according to a preset shape.

[0018] In some alternative implementations, the light emitted from the laser chip passes through a grating, reaches a reflector, and returns after passing through the grating again. The returned beam then falls precisely onto the two detector chips. In this case, the laser chip and the two detector chips in a set of optical transceiver components are in the same plane. Preferably, the laser chip is in the center, and the two detector chips are symmetrically distributed on both sides. However, since the laser emission has an angle, the laser chip and the two detector chips do not necessarily form a straight line.

[0019] In some optional implementations, when multiple sets of laser chips corresponding to multiple sets of optical transceiver components are bonded to the upper ceramic substrate, a preset angle deviation and displacement are introduced so that the zero-order return light of the laser chip will not return to itself. Multiple sets of laser chips share a single electrode drive, and multiple sets of detector chips corresponding to multiple sets of optical transceiver components share a single electrode drive, thereby achieving suppression of laser RIN noise and suppression of detector common-mode noise.

[0020] In some optional implementations, the process of forming the grating interference cavity structure by gold-gold bonding of the MEMS sensing unit and the grating unit includes: photolithography and oxide masking of the silicon wafer to complete the beam pattern fabrication; then, deep silicon etching using the BOSCH process to complete the spring-mass structure fabrication; then, a gold film is deposited on the entire upper surface of the MEMS sensing unit using magnetron sputtering; next, the grating unit with grooves is prepared for fabrication by photolithography of the silicon wafer, first depositing a gold film and then using slow etching to create the bottom grooves; then, the back side of the silicon wafer with grooves is photolithographically etched to achieve a linear grating with a preset shape distribution; finally, the fabricated grating unit and the MEMS sensing unit are aligned and bonded together using a gold-gold bonding process to form a complete grating interference cavity.

[0021] In summary, compared with the prior art, the above-described technical solutions conceived by this invention can achieve the following beneficial effects:

[0022] 1. This invention employs multiple sets of pre-distributed gratings, each with a photoelectric detection unit corresponding to its position, to detect out-of-plane motion of the MEMS sensing unit, significantly improving detection sensitivity. Furthermore, the multi-set distributed grating detection scheme effectively distinguishes tilt errors caused by the out-of-plane motion of the MEMS sensing unit, effectively improving the accelerometer's cross-axis suppression capability.

[0023] 2. This invention integrates upper and lower electrodes on the MEMS sensing unit and the grating unit respectively, and realizes the hardware conditions for electrostatic force closed loop through patterned gold-gold bonding, TSV and wire bonding processes, so that the micro optical accelerometer can work in force balance feedback, optical locking, distance locking or open loop mode. Users can select the working mode of the accelerometer to meet specific applications and operating environments.

[0024] 3. This invention introduces a small-angle deviation and displacement during the packaging of the laser chip, preventing the zero-order return light from the laser chip from returning to itself. Multiple laser chips and multiple detector chips share a single electrode drive, achieving suppression of laser RIN noise and detector common-mode noise, thereby improving the accelerometer's detection sensitivity. Furthermore, multiple ceramic substrates are used to achieve a sandwich-style vertical optoelectronic package for the MEMS sensing unit, grating unit, and detection unit. This type of micro-optical accelerometer has high integration, high process feasibility, good consistency, and is suitable for mass production. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the overall structure of an accelerometer provided in an embodiment of the present invention;

[0026] Figure 2This is a three-dimensional diagram of a grating interference cavity structure formed by gold-gold bonding of a MEMS sensing unit 1 and a grating unit 2, according to an embodiment of the present invention.

[0027] Figure 3 This is a schematic diagram of the optical path detected by a set of optical transceiver components provided in an embodiment of the present invention;

[0028] Figure 4 This is a process flow diagram of a grating interference cavity structure formed by gold-gold bonding of a MEMS sensing unit and a grating unit according to an embodiment of the present invention. In the diagram, (a) is the fabrication of the beam pattern, (b) is the fabrication of the spring-mass structure, (c) is the gold-plated film, (d) is the fabrication of the groove, (e) is the three linear gratings distributed in a triangular pattern, and (f) is the grating interference cavity.

[0029] Among them, 1-MEMS sensing unit, 2-grating unit, 3-detection unit, 4-ceramic substrate, 5-wire bonding, 6-metal shell, 7-reflector, 8-lower metal electrode, 9-spring-mass structure, 10-upper metal electrode, 11-grating, 12-grating support frame, 13-optical transceiver assembly, 14-lower ceramic substrate, 15-upper ceramic substrate, 16-hollow thick ceramic substrate, 17-mass, 18-spring, 19-outer frame, 20-laser chip, 21-detector chip, 22-silicon wafer, 23-mask, 24-gold. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other.

[0031] In the embodiments of the present invention, the preset shape can be a triangle, a regular hexagon, a regular nonagon, a regular dodecagon, etc. The present invention does not limit the uniqueness. The following embodiments use a triangle as an example to describe the technical solution of the present invention in detail.

[0032] like Figure 1 As shown, the micro-optical accelerometer with force balance feedback disclosed in this invention is composed of a MEMS sensing unit 1, a grating unit 2, a detection unit 3 and multiple ceramic substrates 4 for packaging, and is encapsulated in a metal tube shell 6 by wire bonding 5.

[0033] The MEMS sensing unit 1 consists of a reflector 7, a lower metal electrode 8, and a symmetrically distributed spring-mass block structure 9.

[0034] The grating unit 2 consists of an upper metal electrode 10, multiple symmetrically distributed gratings 11, and a grating support frame 12;

[0035] The detection unit 3 consists of multiple sets of optical transceiver components 13 arranged in a triangular pattern;

[0036] The ceramic substrate 4 for packaging consists of a lower ceramic substrate 14 with metal pads, an upper ceramic substrate 15 with metal pads, and a hollow thick ceramic substrate 16. The material can be low temperature co-fired ceramic (LTCC).

[0037] The MEMS sensing unit 1 and the grating unit 2 are bonded together with gold to form a single unit and then adhered to the central region of the lower ceramic substrate 14 with metal pads. The bonding process can employ BCB adhesive bonding or epoxy resin adhesive bonding. The detection unit 3 is adhered to the central region of the upper ceramic substrate 15 with metal pads, and the bonding process can be conductive silver paste curing. The MEMS sensing unit 1 and the grating unit 2 are separated from the detection unit 3, with the spacing determined by the hollow thick ceramic substrate 16.

[0038] like Figure 2 The diagram shows a grating interference cavity structure formed by gold-gold bonding of the MEMS sensing unit 1 and the grating unit 2. The MEMS sensing unit 1 consists of a reflector 7, a lower metal electrode 8, and symmetrically distributed spring-mass structures 9. There are multiple sets of spring-mass structures 9, such as three, six, or nine sets; this embodiment of the invention does not limit the specificity. The cantilever beam-mass structure, such as a serpentine or crab-leg beam structure, is symmetrically distributed along the circumference, enabling the spring-mass structure 9 to perform out-of-plane motion. The reflector 7 and the lower metal electrode 8 are both located on the upper surface of the spring-mass structure 9, and are patterned and gold-plated from the upper surface of the MEMS sensing unit 1. The reflector 7 is located on the mass block 17 at the center of the upper surface of the spring-mass structure 9, and the lower metal electrode 8 is located on other patterned portions of the upper surface of the spring-mass structure 9. The lower metal electrode 8 connects the reflector 7 to the outer frame 19 via the upper surface of the spring 18, achieving electrical connection with the outside world.

[0039] The upper metal electrode 10 is patterned and gold-plated on the lower surface of the grating unit 2, and is electrically connected to the upper surface of the grating unit 2 via TSV technology. Symmetrically distributed gratings 11 are located in the central region of the grating unit 2, and together with the reflector 7 on the upper surface of the MEMS sensing unit 1, they form a grating interference cavity. The length of the interference cavity can change with the movement of the spring-mass structure 9. The grating support frame 12 surrounds the grating unit 2, serving to support the grating and enabling subsequent bonding processes with the MEMS sensing unit 1.

[0040] The lower metal electrode 8 located in the MEMS sensing unit 1 is electrically isolated from the upper metal electrode 10 located in the grating unit 2, and is integrally encapsulated in a metal housing 6 via wire bonding 5 to realize the force balance feedback loop of the micro-optical accelerometer. Combined with the unique grating interference cavity structure in this micro-optical accelerometer, it can operate in different modes: such as force balance feedback, optical locking, distance locking, and open-loop mode. The operating mode of the accelerometer can be selected to meet specific applications and operating environments.

[0041] The gratings 11, symmetrically distributed in the central region of the grating unit 2, are linear gratings uniformly distributed along the circumference in triangular patterns (which can also be expanded to regular hexagons, regular nonagons, regular dodecagons, etc.). The gratings 11 are made of silicon wafers by etching uniformly spaced linear grooves, enabling the splitting and combining of laser light. The uniformly distributed triangular gratings 11 (which can also be expanded to regular hexagons, regular nonagons, regular dodecagons, etc.) and their corresponding optical transceiver components 13 form three (hexagonal, nonagonal, dodecagonal, etc.) detection groups, jointly detecting the movement of the reflector 7 located above the MEMS sensing unit 1, effectively improving the cross-axis suppression ratio of the accelerometer.

[0042] like Figure 3 The diagram shows the optical path of a set of optical transceiver components. The upper optical transceiver component consists of an upper ceramic substrate 15 with metal leads (hidden and not shown), a laser chip 20 and two detector chips 21 located at a designated position on the ceramic substrate.

[0043] One example of laser chip 20 can be a vertical-cavity surface-emitting laser (VCSEL) with a power of 0.1–1 mW and a wavelength of 850 nm. The laser generates a stable, single-mode output laser with an electro-optical conversion efficiency of up to 30%, which helps achieve ultra-low power consumption in the system. Furthermore, the laser provides high-quality TEM00 spatial mode output and a mode field diameter close to the diffraction limit, which improves the interference contrast of the interference light output to detector chip 21, thereby enhancing the sensitivity of the accelerometer.

[0044] The detector chip 21 can be a low-noise silicon photodiode (PD), which has low voltage and current noise levels, allowing the system noise to approach the shot noise limit.

[0045] Multiple sets of optical transceiver components 13 are distributed in a preset shape, such as triangles, regular hexagons, regular nonagons, regular dodecagons, etc., and the position of each set of optical transceiver components 13 corresponds one-to-one with the grating positions 11 symmetrically distributed below. The laser emitted downward from the laser chip 21 passes through the grating interference cavity and is symmetrically split and returned to the target surfaces of the two detector chips 22 in the same set, realizing the displacement detection of the cavity length of the grating interference cavity. When the laser chip 20 is bonded to the upper ceramic substrate 15, a small angular deviation and displacement are introduced, such as 15°±5°, so that the zero-order return light of the laser chip 11 will not return to itself, reducing the power fluctuation of the laser output itself.

[0046] like Figure 4 The diagram shows the process flow of the grating interference cavity structure formed by gold-gold bonding of MEMS sensing unit 1 and grating unit 2. First, photolithography and oxide masking 23 are performed on the silicon wafer 22 to complete the beam pattern fabrication, as shown below. Figure 4 (a) Next, deep silicon etching is performed using the BOSCH process to complete the fabrication of the spring-mass structure, as shown in Figure 1. Figure 4 (b) Next, a 1μm gold film 24 is deposited on the upper surface of the entire MEMS sensing unit using magnetron sputtering, as shown in Figure 24. Figure 4 (c) Next, the fabrication of the grooved grating unit is prepared. After photolithography on the silicon wafer, a gold film is first deposited, and then slow etching is used to create the grooves on the bottom, such as... Figure 4 (d) Next, the back of the silicon wafer with grooves is photolithographically etched to create three linear gratings arranged in a triangular pattern, such as... Figure 4 (e) Next, the fabricated grating unit 2 and MEMS sensing unit 1 are aligned and bonded together using a gold-to-gold bonding process to form a complete grating interference cavity, as shown in the figure. Figure 4 (f) Finally, a laser scribing process can be used to peel the individual grating interference cavities off the entire wafer to complete the subsequent packaging process.

[0047] The specific working principle of this invention is described as follows: When an external acceleration is input, the spring-mass structure in the MEMS sensing unit will generate a micro-displacement out of plane. This displacement will cause a change in the distance between the reflector and the grating unit on the upper surface of the MEMS sensing unit. This change in distance will cause a change in the light intensity detected by the PD detector chip in the detection unit. The electrical signal output by the PD detector can be calculated to achieve open-loop measurement of the external acceleration. On the other hand, the electrical signal output by the PD detector can also be added to the control algorithm and input to the upper and lower electrodes to realize other working modes such as force balance feedback, optical locking, and distance locking, to meet specific applications and operating environments.

[0048] The present invention has the following advantages through the above technical solution:

[0049] First, multiple sets of triangularly distributed gratings are used, each set of gratings has a photoelectric detection unit corresponding to its position to realize the out-of-plane motion detection of the MEMS sensing unit, which greatly improves the detection sensitivity of the accelerometer and the cross-axis suppression capability.

[0050] Secondly, upper and lower electrodes are integrated on the MEMS sensing unit and the grating unit respectively, realizing the hardware conditions for electrostatic force closed loop. This enables the micro-optical accelerometer to work in force balance feedback, optical locking, distance locking or open loop mode. Users can select the accelerometer's working mode to meet specific applications and operating environments.

[0051] Third, a small-angle deviation and displacement were introduced during the packaging of the laser chip to prevent the zero-order return light from the laser chip from returning to itself. Multiple laser chips and multiple detector chips share a single electrode drive, achieving suppression of laser RIN noise and detector common-mode noise, thereby improving the accelerometer's detection sensitivity. Furthermore, a sandwich-style vertical optoelectronic package for the micro-optical accelerometer was achieved using various ceramic substrates. This type of accelerometer has high integration, high process feasibility, good consistency, and is suitable for mass production.

[0052] It should be noted that, depending on the implementation needs, the various steps / components described in this application can be broken down into more steps / components, or two or more steps / components or parts of the operation of steps / components can be combined into new steps / components to achieve the purpose of this invention.

[0053] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A micro-optical accelerometer with force balance feedback, characterized in that, It consists of a MEMS sensing unit (1), a grating unit (2), a detection unit (3) and multiple ceramic substrates for packaging (4), and is encapsulated in a metal tube shell (6) by wire bonding (5); The MEMS sensing unit (1) consists of a reflector (7), a lower metal electrode (8) and a symmetrically distributed spring-mass block structure (9). The reflector (7) is located on the mass block (17) at the center of the upper surface of the spring-mass block structure (9). The grating unit (2) consists of an upper metal electrode (10), multiple symmetrically distributed gratings (11), and a grating support frame (12); The detection unit (3) consists of multiple sets of optical transceiver components (13) arranged in a preset shape. The distribution shape of the multiple sets of gratings (11) is consistent with the distribution shape of the multiple sets of optical transceiver components (13). The symmetrically distributed gratings (11) are located in the central region of the grating unit (2) and together with the reflector (7) on the upper surface of the MEMS sensing unit (1), they form a grating interference cavity. The length of the interference cavity can change with the movement of the spring-mass structure (9). Each set of optical transceiver components (13) consists of a laser chip (20) and two detector chips (21). The position of each set of optical transceiver components (13) corresponds one-to-one with the position of the symmetrically distributed gratings (11) below, and they are arranged in a preset shape. A uniformly distributed grating (11) and a corresponding optical transceiver assembly (13) form multiple sets of detectors to jointly detect the movement of the mirror (7) located above the MEMS sensitive unit (1) in order to improve the cross-axis suppression ratio of the accelerometer. Among them, a grating (11), a laser chip (20) and two detector chips (21) constitute a set of detectors. Multiple sets of detectors are distributed according to a preset shape. The light emitted from the laser chip (20) passes through the grating (11), reaches the mirror (7), and returns. After passing through the grating (11) again, the returning beam is exactly incident on the two detector chips (21). Among them, the laser chip (20) and the two detector chips (21) in a set of optical transceiver assemblies (13) are in a plane. The ceramic substrate (4) for packaging is composed of a lower ceramic substrate (14) with metal pads, an upper ceramic substrate (15) with metal pads, and a hollow thick ceramic substrate (16). The MEMS sensing unit (1) and the grating unit (2) are bonded together as a whole and then attached to the central region of the lower ceramic substrate (14) with metal pads; the detection unit (3) is attached to the central region of the upper ceramic substrate (15) with metal pads; the MEMS sensing unit (1) and the grating unit (2) are separated from the detection unit (3) by the spacing determined by the hollow thick ceramic substrate (16).

2. The micro-optical accelerometer according to claim 1, characterized in that, The spring-mass block structure (9) consists of multiple sets of cantilever beam-mass block structures symmetrically distributed along the circumference, enabling the spring-mass block structure (9) to perform out-of-plane motion. The reflector (7) and the lower metal electrode (8) are both located on the upper surface of the spring-mass structure (9) and are patterned and gold-plated from the upper surface of the MEMS sensing unit (1). The lower metal electrode (8) is located on other patterned parts of the upper surface of the spring-mass structure (9). The lower metal electrode (8) connects the reflector (7) to the outer frame (19) via a spring (18).

3. The micro-optical accelerometer according to claim 2, characterized in that, The upper metal electrode (10) is patterned and gold-plated on the lower surface of the grating unit (2), and is electrically connected to the upper surface of the grating unit (2) through the TSV process. The grating support frame (12) is the area surrounding the grating unit (2), which serves to support the grating and to achieve bonding connection with the MEMS sensitive unit (1).

4. The micro-optical accelerometer according to claim 3, characterized in that, The lower metal electrode (8) located in the MEMS sensing unit (1) is electrically isolated from the upper metal electrode (10) located in the grating unit (2), and is encapsulated in a metal tube shell (6) by wire bonding (5) to realize the force balance feedback loop of the micro-optical accelerometer.

5. The micro-optical accelerometer according to claim 4, characterized in that, The gratings (11) symmetrically distributed in the central region of the grating unit (2) are linear gratings uniformly distributed along the circumference according to a preset shape. The gratings (11) are made by etching uniformly spaced linear grooves on a silicon wafer to realize the function of splitting and combining laser light.

6. The micro-optical accelerometer according to claim 5, characterized in that, When multiple sets of optical transceiver components (13) and multiple sets of laser chips (20) are bonded to the upper ceramic substrate (15), a preset angle deviation and displacement are introduced, so that the zero-order return light of the laser chip (20) will not return to itself. Multiple sets of laser chips (20) share a single electrode for driving, and multiple sets of detector chips (21) and multiple sets of optical transceiver components (13) share a single electrode for driving.

7. The micro-optical accelerometer according to claim 3, characterized in that, The process of forming a grating interference cavity structure by gold-gold bonding of the MEMS sensing unit (1) and the grating unit (2) includes: photolithography and oxide masking of the silicon wafer to complete the beam pattern fabrication; then using the BOSCH process to achieve deep silicon etching to complete the spring-mass block structure fabrication; then using magnetron sputtering to deposit a gold film on the upper surface of the entire MEMS sensing unit; then preparing to fabricate the grating unit with grooves, photolithography of the silicon wafer, first depositing a gold film and then using slow etching to achieve the bottom groove fabrication; then photolithography etching of the back side of the silicon wafer with grooves to achieve a linear grating with a preset shape distribution; then aligning and bonding the fabricated grating unit (2) and the MEMS sensing unit (1) together using the gold-gold bonding process to form a complete grating interference cavity.

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