A MEMS relative gravimeter probe and gravimeter based on variable area comb capacitors

Abstract

The present invention discloses a MEMS relative gravimeter probe and a gravimeter based on a variable area comb capacitor, belonging to the field of instruments. The probe includes: a spring structure, a proof mass, movable comb teeth, fixed comb teeth and an outer frame. The fixed end of the spring structure is arranged on the outer frame, and the free end is connected to the proof mass. The movable comb teeth are arranged on the upper and lower surfaces of the proof mass, and the fixed comb teeth are correspondingly arranged on the outer frame. Both the movable comb teeth and the fixed comb teeth are of special-shaped comb tooth structures. The special-shaped comb tooth structure includes bottom comb teeth and top comb teeth, and the width of the bottom comb teeth is smaller than that of the top comb teeth. The bottom comb teeth of the movable comb teeth are fixed on the proof mass, and the bottom comb teeth of the fixed comb teeth are fixed on the outer frame. During operation, the top comb teeth of the movable comb teeth and the top comb teeth of the fixed comb teeth form a variable area differential comb capacitor structure. The present invention can improve the sensitivity of capacitive displacement sensing and reduce the mechanical thermal noise of the gravimeter probe.

Description

Technical Field

[0001] The present invention belongs to the field of instruments and meters, and more specifically, relates to a variable-area comb-tooth capacitive MEMS relative gravimeter probe and a gravimeter applied to precise gravity measurement. Background Art

[0002] The distribution of the gravitational field depends on the composition and distribution of the materials inside the Earth. Accurately measuring the spatial distribution and its time-varying characteristics of the gravitational field is of great significance for Earth science research, disaster warning, geodetic surveying, weapon guidance, ocean exploration, resource exploration, etc.

[0003] MEMS (Micro-Electro-Mechanical System) sensors use chip technology to design and process sensing probes, and have the advantages of small size, low cost, easy integration with circuits, and easy mass production. In recent years, the rapid development of MEMS technology and sensing technology has significantly improved the resolution and stability of MEMS accelerometers, and they have been applied in precise gravity measurement.

[0004] The University of Glasgow and Huazhong University of Science and Technology both use the light-blocking method for displacement sensing to develop an open-loop MEMS gravimeter (Tang Shihao et al. Microsystems & nanoengineering, 2019, 5(1), 1-11; Middlemiss RP et al. Nature, 2016, 531(7596): 614–617.), but this gravimeter has problems such as low displacement sensing accuracy and slow response speed.

[0005] Adopting the force balance working mode can significantly improve key performance parameters such as the response speed and linearity of the gravimeter. Imperial College London proposed a high-precision MEMS accelerometer (seismometer) based on surface array capacitive displacement sensing and magnetic closed-loop feedback control for the application requirements of Mars exploration (US20030140699 A1), which significantly improves the acceleration sensing accuracy and response speed. However, the magnetic pole has a large volume and is difficult to integrate, and the magnetic field is easily affected by temperature. The comb-tooth accelerometer uses comb-tooth capacitors to achieve displacement sensing and electrostatic feedback force balance control (CN101839923A, CN102156201A), and has the advantages of fast response speed, simple film layer structure, and low power consumption. However, due to the thin device layer and small oscillator mass, the comb-tooth accelerometer has high thermal noise and poor accuracy. Summary of the Invention

[0006] Aiming at the defects and improvement requirements of the existing technology, the present invention provides a MEMS relative gravimeter probe and a gravimeter based on variable-area comb-tooth capacitors, aiming to improve the sensitivity of capacitive displacement sensing and reduce the mechanical thermal noise of the gravimeter probe.

[0007] To achieve the above object, according to one aspect of the present invention, there is provided a MEMS relative gravimeter probe based on variable area comb capacitors, including a spring structure, a proof mass, moving comb teeth, fixed comb teeth and an outer frame. The fixed end of the spring structure is arranged on the outer frame, and the free end is connected to the proof mass. The moving comb teeth are arranged on the upper and lower surfaces of the proof mass, and the fixed comb teeth are correspondingly arranged on the outer frame.

[0008] Among them, both the moving comb teeth and the fixed comb teeth are special-shaped comb tooth structures. The special-shaped comb tooth structure includes bottom comb teeth and top comb teeth, and the width of the bottom comb teeth is smaller than that of the top comb teeth. The bottom comb teeth of the moving comb teeth are fixed on the proof mass, and the bottom comb teeth of the fixed comb teeth are fixed on the outer frame.

[0009] During operation, the spring structure is used to convert the change in the measured gravitational acceleration into the displacement change of the proof mass. The top comb teeth of the moving comb teeth and the top comb teeth of the fixed comb teeth form a variable area differential comb capacitor structure, which is used to convert the displacement change into a differential capacitance signal.

[0010] Furthermore, the central axes of the bottom comb teeth and the top comb teeth coincide.

[0011] Furthermore, the following relationship is satisfied among the positive facing distance d0 between the top comb teeth of the moving comb teeth and the fixed comb teeth, the width w1 of the bottom comb teeth, and the width w2 of the top comb teeth:

[0012] w2 - w1 = 2(n - 1)d0

[0013] Wherein, d1 represents the positive facing distance between the top comb teeth of the fixed comb teeth and the bottom comb teeth of the moving comb teeth when the fixed comb teeth and the moving comb teeth are arranged in a cross pattern.

[0014] Furthermore, the length of the bottom comb teeth is greater than that of the top comb teeth.

[0015] Furthermore, the materials of the spring structure, the proof mass, the moving comb teeth, the fixed comb teeth and the outer frame are SOI.

[0016] Furthermore, the thickness of the moving comb teeth and the fixed comb teeth is 50μm - 2000μm.

[0017] Furthermore, the following relationship is satisfied among the output ΔC of the differential comb capacitor, the positive facing distance d0 between the top comb teeth of the moving comb teeth and the fixed comb teeth, and the thickness h of the moving comb teeth and the fixed comb teeth:

[0018]

[0019] Wherein, ε is the dielectric constant, Δx is the moving displacement of the proof mass, and N represents the number of array capacitor plate groups of the differential comb capacitor.

[0020] Furthermore, it also includes a back-end circuit module, which includes a capacitive sensing unit, a feedback control unit and an electrostatic feedback actuator;

[0021] The capacitance sensing unit is used to detect the differential capacitance signal and convert the differential capacitance signal into an analog voltage signal;

[0022] The feedback control unit is used to determine the amount by which the proof mass deviates from the equilibrium position according to the analog voltage signal, and to calculate the feedback voltage required to return the proof mass to the equilibrium state through feedback regulation output;

[0023] The electrostatic feedback actuator is used to receive the feedback voltage and generate an electrostatic feedback force to control the proof mass to maintain at a balanced position according to a relationship between the feedback voltage and the electrostatic feedback force.

[0024] Furthermore, the electrostatic feedback force F and the acceleration change Δg to be measured satisfy:

[0025]

[0026] Where m is the mass of the inspection mass, V f is the feedback voltage, V b The DC feedback bias voltage applied to the top comb teeth of the fixed comb teeth is provided by an external power supply, N represents the number of array capacitor plate groups of the differential comb teeth capacitor, ε is the dielectric constant, h is the thickness of the movable comb teeth and the fixed comb teeth, and d0 is the top comb teeth facing distance between the movable comb teeth and the fixed comb teeth.

[0027] According to another aspect of the present invention, a MEMS relative gravimeter based on variable area comb capacitance is provided, comprising a probe, wherein the probe is the probe described in any one of the first aspects.

[0028] In general, the above technical solutions conceived by the present invention can achieve the following beneficial effects:

[0029] (1) The probe of the present invention is designed to have a special-shaped comb tooth structure by designing the movable comb teeth and the fixed comb teeth. The bottom comb teeth of the special-shaped comb tooth structure have a width smaller than the top comb teeth. During etching, the bottom comb teeth of the fixed comb teeth face the top comb teeth of the movable comb teeth, and the top comb teeth of the fixed comb teeth face the bottom comb teeth of the movable comb teeth. Compared with the conventional comb tooth capacitive accelerometer, the facing distance between the movable comb teeth and the fixed comb teeth is larger. Under the same aspect ratio condition, the etching depth can be increased, so that the device of the present invention can use the thick silicon layer of the SOI silicon wafer. On this basis, the quality of the inspection mass can be increased and the mechanical thermal noise can be reduced.

[0030] (2) The probe of the present invention uses the displacement of the inspection mass under the action of gravity to lock the moving comb teeth into the fixed comb teeth. The top comb teeth of the moving comb teeth at the upper and lower ends of the inspection mass have the same facing area with the fixed comb teeth, reaching a balanced state. When an acceleration signal is input from the outside, the acceleration signal to be measured is converted into a displacement signal through the spring structure. The top comb teeth of the fixed comb teeth and the moving comb teeth form a variable-area differential capacitance structure. Compared with the initial etching state, the comb tooth gap is reduced, the displacement sensing sensitivity is increased, and the limitation of the limited depth-width ratio of reactive ion deep etching on the comb tooth pitch of the thick device layer is overcome, enabling high-sensitivity force-balanced gravitational acceleration sensing.

[0031] (3) Further, based on the special-shaped comb teeth designed in the present invention, a closed-loop control between the acceleration change to be measured and the electrostatic feedback force is realized by matching the backend circuit module that at least includes three parts: capacitance sensing, feedback control, and electrostatic feedback actuator. Compared with the open-loop control, it can improve the response speed and anti-interference ability of the gravimeter. Compared with the electromagnetic closed-loop feedback control, this structure does not require separately manufacturing the capacitive moving electrode plate and the fixed electrode plate on the silicon-based material and the glass cover, simplifies the processing technology, and reduces the volume of the device. Description of the Drawings

[0032] Figure 1 Schematic diagram of the probe structure of the MEMS relative gravimeter based on variable-area comb tooth capacitance of the present invention.

[0033] Figure 2 Schematic diagram of the special-shaped comb tooth structure of the present invention.

[0034] Figure 3 Schematic diagram of the variable-area comb tooth capacitance of the present invention under the condition of no gravity (processing state).

[0035] Figure 4 Schematic diagram of the variable-area comb tooth capacitance of the present invention reaching a balanced state under the action of gravity.

[0036] Figure 5 Schematic diagram of the closed-loop control process of the gravimeter probe of the present invention.

[0037] In all the drawings, the same reference numerals are used to represent the same elements or structures, where:

[0038] 1 - Spring structure, 2 - Inspection mass, 3 - Moving comb teeth, 4 - Upper fixed comb teeth, 5 - Lower fixed comb teeth, 6 - Outer frame, 7 - Top comb teeth, 8 - Bottom comb teeth. Detailed Embodiments

[0039] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present 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 only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0040] In the present invention, terms such as "first" and "second" in the present invention and the accompanying drawings are used to distinguish similar objects and do not necessarily need to describe a specific order or sequence.

[0041] As Figure 1-2 shown, the MEMS relative gravity probe based on variable area comb capacitors of the present invention mainly includes: a spring structure 1, a proof mass 2, moving comb teeth 3, fixed comb teeth, and an outer frame 6. The fixed end of the spring structure 1 is provided on the outer frame 6, and the free end is connected to the proof mass 2. The moving comb teeth 3 are provided on the upper and lower surfaces of the proof mass 2. The fixed comb teeth include an upper fixed comb tooth 4 and a lower fixed comb tooth 5, which are respectively provided on the outer frame 6. Differential comb capacitors are formed by the moving comb teeth 3 on the upper and lower surfaces of the proof mass 2 and the corresponding upper fixed comb tooth 4 and lower fixed comb tooth 5 respectively. Among them, both the moving comb teeth and the fixed comb teeth are special-shaped comb tooth structures. The special-shaped comb tooth structure includes an integrated bottom comb tooth 8 and a top comb tooth 7. The central axes of the bottom comb tooth and the top comb tooth coincide. The width of the bottom comb tooth is smaller than the width of the top comb tooth, and the bottom comb tooth is fixed on the proof mass or the outer frame, that is, the bottom comb tooth of the moving comb tooth is fixed on the proof mass, and the bottom comb tooth of the fixed comb tooth is fixed on the outer frame. During operation, the top comb teeth of the moving comb teeth at the upper and lower ends of the proof mass and the top comb teeth of the fixed comb teeth of the outer frame form a variable area differential comb capacitor structure.

[0042] Preferably, the length of the bottom comb tooth is greater than the length of the top comb tooth. When processing the comb capacitor, it is convenient to achieve equal width of the etched area, consistent etching rate, and uniform morphology of each etched comb tooth, which can improve the detection accuracy of the capacitor plates. It should be noted that the width in the present invention refers to the dimension along the x-axis direction, and the length refers to the dimension along the y-axis direction.

[0043] The proof mass, the moving comb teeth, and the spring structure are processed and suspended by DRIE (Deep Reactive Ion Etching). Relative to the outer frame part, this part can undergo displacement vibration.

[0044] The proof mass is used to detect the acceleration signal to be measured, convert the acceleration to be measured into the displacement change of the proof mass, convert the displacement change into the capacitance through the differential comb capacitor, and then convert the detected capacitance change into a voltage signal output through a matching circuit, and finally obtain the corresponding acceleration after data processing.

[0045] When the comb capacitors of the present invention are processed, the fixed comb teeth and the movable comb teeth are arranged in a cross pattern, that is, the fixed comb teeth and the movable comb teeth are completely buckled together. The bottom comb teeth of the fixed comb teeth face the top comb teeth of the movable comb teeth, and the top comb teeth of the fixed comb teeth face the bottom comb teeth of the movable comb teeth. At this time, the facing distance between the comb teeth of the fixed comb teeth and the movable comb teeth is the same, denoted as d1. The width of the bottom comb teeth in the movable comb teeth and the fixed comb teeth is w1, and the width of the top comb teeth is w2, where w1 < w2. As Figure 3 shown, since the width of the bottom comb teeth is less than that of the top comb teeth, when etching, the fixed comb teeth and the movable comb teeth are arranged in a cross pattern. Compared with the capacitors with the existing equal-width comb tooth structures for both the fixed comb teeth and the movable comb teeth, the facing distance between the comb teeth of the present invention can be larger when designing and processing the layout, which is beneficial to reducing the limitation of the aspect ratio of the area to be etched and alleviating process problems such as release adhesion.

[0046] As Figure 4 shown, due to the action of the inspection mass gravity, the movable comb teeth move downward. When the probe of the present invention is in balance, the facing areas of the movable comb teeth at the upper and lower ends of the inspection mass and the top comb teeth of the fixed comb teeth are the same, forming a differential variable area capacitance structure. Denote the facing distance between the top comb teeth between the movable comb teeth and the fixed comb teeth as d0. Then, at this time, the facing distance between the movable comb teeth and the fixed comb teeth is reduced compared with the initial plate distance d1, which improves the sensitivity of the differential comb capacitance structure and increases the front-end gain of the entire system.

[0047] To achieve the effect of reducing the comb tooth spacing by n times, that is, d1 = nd0, the relationship between the widths of the bottom comb teeth and the top comb teeth satisfies:

[0048] w2 - w1 = 2(n - 1)d0

[0049] When the probe of the present invention is working, when there is an acceleration signal input from the outside, the acceleration signal to be measured is converted into a displacement signal through the spring structure, and then the displacement signal is converted into a capacitance signal through the comb capacitor plates. The comb teeth arranged symmetrically up and down form a differential capacitance structure. Through differential, most of the interference noises can be eliminated, and the signal-to-noise ratio is improved. The relationship between the differential capacitance output and the displacement of the array capacitor plates composed of N groups of variable area comb capacitor plates is:

[0050]

[0051] In the formula, ε is the dielectric constant of the capacitive medium. It can be seen from this formula that the differential capacitance is proportional to the number of pairs N of the comb capacitor plates, the moving displacement Δx of the inspection mass, and the comb thickness h, and is inversely proportional to the spacing d0 when the top comb teeth of the movable comb teeth and the fixed comb teeth face each other.

[0052] Therefore, compared with the equal-width comb-tooth structure capacitor in the prior art, the comb-tooth capacitor of the present invention has a smaller comb-tooth pitch during operation, which can improve the displacement sensing sensitivity and reduce mechanical thermal noise. This "irregular" snap-in comb-tooth capacitor design of the present invention enables the moving comb teeth to move downward during the operation of the probe, forming a differential capacitance structure with the upper fixed comb teeth and the lower fixed comb teeth. Most of the interference noise can be eliminated through the differential, improving the signal-to-noise ratio.

[0053] In this embodiment, the spring structure includes four groups of springs, which are symmetrically arranged on both sides of the outer frame in pairs. Under the action of the self-gravity of the inspection mass, each group of springs deforms to generate a resultant force, which cancels out the gravity of the inspection mass to achieve quasi-zero stiffness.

[0054] In this embodiment, the material of the entire device is preferably SOI, and the thickness of the device, that is, the comb-tooth thickness h, is a SOI silicon wafer with a thickness of 50 μm to 2000 μm. Since the comb-tooth capacitor of the present invention has a larger facing pitch between the comb teeth during etching, compared with the conventional comb-tooth capacitor accelerometer, under the same etching aspect ratio limit, the present invention has a wider etching width, so the etching depth can be increased, enabling the device of the present invention to use the thick silicon layer of the SOI silicon wafer. On this basis, the mass of the inspection mass can be increased, significantly reducing mechanical thermal noise.

[0055] At the same time, for the variable-area comb-tooth capacitor design, the facing area of the comb-tooth capacitor can be increased to improve the capacitance displacement sensing sensitivity.

[0056] Compared with the magnetic feedback control method, the MEMS gravity sensing chip film structure of the present invention is simple, directly etching comb teeth on silicon, generating less heat, which is beneficial to improving long-term stability. In addition, it also avoids environmental disturbance problems such as temperature effects and magnetic effects introduced by permanent magnets in magnetic feedback control.

[0057] The device of the present invention can adopt the thick silicon layer design of the SOI silicon wafer to increase the mass of the inspection mass, thereby reducing mechanical thermal noise; adopting an irregular comb-tooth design to construct a differential displacement sensor, using the displacement of the inspection mass under the action of gravity to snap the moving comb teeth into the fixed comb teeth, reducing the comb-tooth gap to increase the displacement sensing sensitivity, overcoming the limitation of the limited etching aspect ratio of reactive ion deep etching on the comb-tooth pitch of the thick device layer, and finally achieving high-sensitivity force balance type gravity acceleration sensing.

[0058] Based on the above-mentioned irregular comb teeth design, the probe of the present invention also matches a backend circuit module that at least includes a capacitance sensing unit, a feedback control unit, and an electrostatic feedback actuator to achieve the electrostatic closed-loop control of the entire probe. The fixed comb teeth are distributed up and down, and the fixed teeth of the same polarity are connected together. When the gravimeter operates in a closed loop, opposite feedback voltages V are applied to the top comb teeth of the upper fixed comb teeth and the top comb teeth of the lower fixed comb teeth respectively. f, an electrostatic feedback force F is generated to balance the inertial force brought by the acceleration to be measured. The top comb teeth of the upper fixed comb teeth and the top comb teeth of the lower fixed comb teeth are both for detection and can also be used for feedback.

[0059] Specifically, as Figure 5 shown, during operation, the spring structure senses the change in the acceleration of gravity to be measured and converts it into a displacement change Δx of the spring structure, driving the proof mass to move between the frames. The variable area differential comb tooth capacitor structure formed by the top comb teeth of the moving comb teeth and the top comb teeth of the fixed comb teeth converts this displacement change into a differential capacitance signal. This differential capacitance signal is related to the residual acceleration signal provided by the detection spring structure, the proof mass, and the comb teeth. Among them, the residual acceleration signal is the magnitude of the external input acceleration signal in the sensitive axis direction;

[0060] The capacitance sensing unit detects this differential capacitance signal and converts it into an analog voltage signal;

[0061] The feedback control unit judges the amount by which the proof mass deviates from the equilibrium position based on the analog voltage signal, and outputs a calculation through feedback regulation to obtain the feedback voltage V required for the proof mass to return to the equilibrium state f ; among them, in this embodiment, the feedback regulation control adopts the PID control algorithm.

[0062] After receiving the feedback voltage, the electrostatic feedback actuator generates a corresponding electrostatic feedback force according to the relationship between the feedback voltage and the electrostatic feedback force F to control the proof mass to stay at the equilibrium position, realizing the closed-loop control between the change in the acceleration to be measured and the electrostatic feedback force.

[0063] Among them, the relationship between the feedback voltage and the electrostatic feedback force F is:

[0064]

[0065] In the formula, V f is the feedback voltage applied to the top comb teeth of the fixed comb teeth, V p is the amplitude of the high-frequency carrier signal applied to the top comb teeth of the fixed comb teeth, and V b is the DC feedback bias voltage provided by the external power supply and applied to the top comb teeth of the fixed comb teeth.

[0066] Since the carrier frequency is much higher than the spring oscillator response frequency, the influence of the electrostatic feedback force generated by V p can be ignored. Then the electrostatic feedback force F is:

[0067]

[0068] Wherein, m is the mass of the test mass, Δg is the change in the gravitational acceleration to be measured, N represents the number of array capacitor plate groups of the differential comb capacitors, ε is the dielectric constant, h is the thickness of the moving comb teeth and the fixed comb teeth, and d0 is the top comb facing distance between the moving comb teeth and the fixed comb teeth.

[0069] By using the electrostatic closed-loop feedback to control the sensitive unit at the equilibrium position, the present invention can improve the response speed and anti-interference ability of the gravimeter compared with the open-loop control; compared with the electromagnetic closed-loop feedback, this structure does not require separately fabricating the movable capacitor plates and the fixed capacitor plates on the silicon-based material and the glass cover, which simplifies the processing technology and reduces the volume of the device.

[0070] The present invention also provides a MEMS relative gravimeter based on variable area comb capacitors, including a probe, and the probe is the probe described above.

[0071] Those skilled in the art can easily understand that the above are only preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A MEMS relative gravimeter probe based on variable area comb capacitors, characterized in that, It includes a spring structure (1), a proof mass (2), moving comb teeth (3), fixed comb teeth, and an outer frame (6). The fixed end of the spring structure (1) is set on the outer frame (6), and the free end is connected to the proof mass (2). The moving comb teeth (3) are arranged on the upper and lower surfaces of the proof mass (2), and the corresponding fixed comb teeth are arranged on the outer frame (6). Among them, both the moving comb teeth and the fixed comb teeth are special-shaped comb tooth structures. The special-shaped comb tooth structure includes bottom comb teeth (8) and top comb teeth (7), and the width of the bottom comb teeth (8) is smaller than that of the top comb teeth (7). The bottom comb teeth of the moving comb teeth are fixed on the proof mass, and the bottom comb teeth of the fixed comb teeth are fixed on the outer frame. During etching, the bottom comb teeth of the fixed comb teeth face the top comb teeth of the moving comb teeth, and the top comb teeth of the fixed comb teeth face the bottom comb teeth of the moving comb teeth. During operation, the displacement of the proof mass under the action of gravity is used to engage the moving comb teeth into the fixed comb teeth. The facing areas of the top comb teeth of the moving comb teeth at the upper and lower ends of the proof mass and the fixed comb teeth are the same to reach a balanced state. When the acceleration due to gravity to be measured is input, the spring structure is used to convert the change in the acceleration due to gravity to be measured into a displacement change of the proof mass. The top comb teeth of the moving comb teeth and the top comb teeth of the fixed comb teeth form a variable-area differential comb tooth capacitor structure, which is used to convert the displacement change into a differential capacitance signal.

2. The probe according to claim 1, wherein, The central axes of the bottom comb teeth (8) and the top comb teeth (7) coincide.

3. The probe according to claim 2, characterized in that The facing distance d0 between the top comb teeth, the width w1 of the bottom comb teeth, and the width w2 of the top comb teeth between the moving comb teeth and the fixed comb teeth satisfy: w2 - w1 = 2(n - 1)d0 Among them, d1 represents the facing distance between the top comb teeth of the fixed comb teeth and the bottom comb teeth of the movable comb teeth when the fixed comb teeth and the movable comb teeth are arranged crosswise.

4. The probe according to claim 2, characterized in that, The length of the bottom comb teeth is greater than that of the top comb teeth.

5. The probe according to claim 1, characterized in that, The materials of the spring structure, the proof mass, the moving comb teeth, the fixed comb teeth, and the outer frame are SOI.

6. The probe according to claim 5, characterized in that, The thickness of the moving comb teeth and the fixed comb teeth is 50 μm to 2000 μm.

7. The probe according to claim 6, characterized in that, The output ΔC of the differential comb tooth capacitor, the facing distance d0 between the top comb teeth between the moving comb teeth and the fixed comb teeth, and the thickness h of the moving comb teeth and the fixed comb teeth satisfy: Among them, ε is the dielectric constant, Δx is the moving displacement of the proof mass, and N represents the number of array capacitor plate groups of the differential comb tooth capacitor.

8. The probe according to claim 1, characterized in that It further includes a backend circuit module. The backend circuit module includes a capacitance sensing unit, a feedback control unit, and an electrostatic feedback actuator. The capacitance sensing unit is used to detect the differential capacitance signal and convert the differential capacitance signal into an analog voltage signal. The feedback control unit is used to judge the amount by which the proof mass deviates from the balanced position according to the analog voltage signal, and output a calculated feedback voltage required to return the proof mass to the balanced state through feedback regulation. The electrostatic feedback actuator is used to receive the feedback voltage and generate an electrostatic feedback force that controls the proof mass to stay at the balanced position according to the relationship between the feedback voltage and the electrostatic feedback force.

9. The probe according to claim 8, wherein, The electrostatic feedback force F and the change Δg in the acceleration to be measured satisfy: where m is the mass of the test mass, V f is the feedback voltage, V b is the DC feedback bias voltage applied to the top comb teeth of the fixed comb teeth provided by the external power supply. N represents the number of array capacitor plate groups of the differential comb teeth capacitance, ε is the dielectric constant, h is the thickness of the moving comb teeth and the fixed comb teeth, and d0 is the facing distance between the top comb teeth between the moving comb teeth and the fixed comb teeth.

10. A MEMS relative gravimeter based on variable area comb capacitors, comprising a probe, characterized in that, The probe is the probe according to any one of claims 1-9.

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