A system and method for measuring electrode gap in a capacitive MEMS structure

Abstract

The application discloses a kind of electrode gap measurement system and method of capacitive MEMS structure, the system includes: measurement signal generation unit, for generating the capacitive signal reflecting electrode gap information;Signal processing circuit is used to process the generated capacitive signal, convert capacitive signal into readable, high signal-to-noise ratio analog voltage signal;Data processing unit is used to carry out data processing to analog voltage signal, and the electrode gap value is calculated to obtain.This application is applied to the field of MEMS structure, based on the idea of resonance, one of MEMS structure or adjustable capacitor is in dynamic change state, output only contains the signal of MEMS structure or adjustable capacitor capacitance change part and is the signal under the condition of maximum amplitude, not only can high signal-to-noise ratio capacitive signal be obtained by resonance amplification, but also the influence of parasitic capacitance can be avoided, and high-precision, high-resolution measurement of dynamic or static capacitive MEMS structure electrode gap is realized.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of MEMS structure, and particularly relates to a capacitive MEMS structure electrode gap measuring system and method. BACKGROUND

[0002] MEMS (Micro-Electro-Mechanical System) devices have become a research hotspot in the field of inertial measurement because of the advantages of small volume, low cost, high performance, easy batch manufacturing and integration, and are widely applied to the fields of consumer electronics, inertial navigation, automobile industry and the like. According to the detection mode, the MEMS structure can be classified into capacitive, optical fiber, piezoelectric, piezoresistive and tunnel effect types, wherein the capacitive structure has the advantages of high detection sensitivity, small power consumption and good temperature stability, and becomes one of the main detection modes, and is widely applied in the current silicon-based MEMS structure because of the unique advantages of the structure and working characteristics.

[0003] The electrode is an important component of the capacitive MEMS structure, and the researches on the electrode are mainly concentrated in the aspects of structure form selection (such as tuning fork type, flat plate type), size parameter design, error analysis and assembly precision and the like, which directly affect the key technical indexes of the MEMS device. However, the electrode gap connecting the theoretical analysis of the MEMS device with the actual performance is rarely researched. At present, one common method is to directly measure the electrode gap by destroying the MEMS structure by using an optical microscope, a scanning electron microscope (SEM) and an atomic force microscope (AFM), for the micrometer-level structure, the destruction of the structure may cause deformation or adhesion and particle pollution to limit the measurement accuracy, on the other hand, the instrument measurement method has high requirements for the precision of the instrument itself and the proficiency of the user operation, and also affects the further improvement of the measurement accuracy and brings the time-consuming deficiency. Another method is to measure the electrode gap by using an electrical measurement method, which does not need to destroy the structure to measure, and generally calibrates the electrode gap by measuring the static capacitance, but the method has the disadvantage of low resolution due to the influence of the parasitic capacitance. SUMMARY

[0004] In view of the deficiencies in the prior art, the application provides a capacitive MEMS structure electrode gap measuring system and method, which is applied to the measurement of the electrode gap of the capacitive MEMS structure, eliminates the influence of the parasitic capacitance based on the resonance principle of the MEMS structure, realizes the high-resolution and high-precision measurement of the electrode gap in the capacitive MEMS structure, can also simultaneously adapt to the electrode gap measurement of the dynamic or static MEMS structure, improves the universality of the method, and can not only be used for the mechanism and performance analysis of the MEMS structure, but also provide an important reference for the design optimization of the MEMS device.

[0005] To achieve the above object, the application provides a capacitive MEMS structure electrode gap measurement system, comprising:

[0006] a measurement signal generation unit for generating a capacitive signal reflecting electrode gap information;

[0007] a signal processing circuit for processing the capacitive signal generated by the measurement signal generation unit, converting the capacitive signal into a readable, high signal-to-noise ratio analog voltage signal;

[0008] a data processing unit for data processing the analog voltage signal, calculating the electrode gap value.

[0009] In one embodiment, the measurement signal generation unit comprises a drive modulation module, a MEMS structure to be measured and an adjustable capacitor.

[0010] The drive modulation module is used to generate a drive voltage containing three different signals of direct current, alternating current and high-frequency carrier wave, and to make the MEMS structure to be measured and the adjustable capacitor generate a capacitive signal through the drive voltage, and to modulate the capacitive signal after the difference between the two.

[0011] In one embodiment, the capacitance of the adjustable capacitor is adjustable, and the principle and size of the capacitance adjustment of the adjustable capacitor are determined by the MEMS structure to be measured, specifically:

[0012] When the MEMS structure to be measured is in a dynamic state, the capacitance of the adjustable capacitor is equal to the static capacitance of the MEMS structure to be measured.

[0013] When the MEMS structure to be measured is in a static state, the capacitance of the adjustable capacitor fluctuates above and below the static capacitance of the MEMS structure to be measured.

[0014] In one embodiment, the signal processing circuit comprises:

[0015] a C / V conversion module for amplifying and converting the modulated weak capacitive signal into a high-frequency voltage signal;

[0016] a high-pass filtering and amplifying module for filtering low-frequency noise in the high-frequency voltage signal and amplifying the filtered high-frequency voltage signal;

[0017] a demodulation module for demodulating the filtered high-frequency voltage signal to obtain a low-frequency voltage signal;

[0018] a phase compensation module for correcting the phase information in the demodulated signal to further improve the signal accuracy containing the electrode gap information;

[0019] a low-pass filter and amplifier module for filtering and amplifying high-frequency noise in the low-frequency voltage signal to obtain a voltage signal with high signal-to-noise ratio and containing electrode gap information;

[0020] In the voltage signal containing electrode gap information, when the MEMS structure under test is in dynamic state, the electrode gap information comes from the capacitance variation amount generated by the displacement of the moving structure; when the MEMS structure under test is in static state, the electrode gap information comes from the capacitance variation amount generated by the capacitance adjustment of the adjustable capacitor.

[0021] In one of the embodiments, when the data processing unit performs data processing, the data processing unit derives a mathematical relationship between the voltage signal with high signal-to-noise ratio and containing electrode gap information and the electrode gap according to the dynamic model of the MEMS structure under test, and then calibrates the electrode gap accurately based on the mathematical relationship and known structure and circuit parameters.

[0022] In one of the embodiments, the derivation process of the mathematical relationship is as follows:

[0023] According to the input driving voltage size and structure size parameters, the driving force is calculated.

[0024] According to the dynamic equation of the MEMS structure under test, the displacement variation amount of the moving part of the MEMS structure under the driving force is calculated, or the system displacement variation amount calculated according to the MEMS structure area and the capacitance variation of the adjustable capacitor.

[0025] Since the displacement variation amount is related to the capacitance gap, and the displacement variation amount actually reflects the output signal obtained through the signal processing circuit, the mathematical relationship between the voltage signal with high signal-to-noise ratio and containing electrode gap information and the electrode gap can be established based on the capacitance calculation formula.

[0026] To achieve the above-mentioned purpose, the application further provides a method for measuring the electrode gap of a capacitive MEMS structure, which adopts the capacitive MEMS structure electrode gap measurement system described above, and the measurement method comprises the following steps:

[0027] Step 1: generating a capacitance signal reflecting electrode gap information based on the measurement signal generation unit;

[0028] Step 2: processing the capacitance signal generated by the measurement signal generation unit based on the signal processing circuit, and converting the capacitance signal into an analog voltage signal with high signal-to-noise ratio and readability;

[0029] Step 3: performing data processing on the analog voltage signal based on the data processing unit, and calculating the electrode gap value.

[0030] In one of the embodiments, the process of Step 1 is specifically as follows:

[0031] The driving modulation module generates a driving voltage containing direct current, alternating current and high-frequency carrier wave;

[0032] The driving voltage is applied to the MEMS structure and the adjustable capacitor respectively, so that the MEMS structure and the adjustable capacitor generate a capacitance signal, and the signal after the difference between the two is modulated;

[0033] After the driving voltage is applied to the MEMS structure and the adjustable capacitor respectively, the MEMS structure is in a dynamic state and the capacitance value of the adjustable capacitor is equal to the static capacitance value of the MEMS structure, or the MEMS structure is in a static state and the adjustable capacitor is in a dynamic state, wherein the capacitance value of the adjustable capacitor in the dynamic state fluctuates above and below the static capacitance of the MEMS structure.

[0034] In one embodiment, the process of step 2 is specifically:

[0035] The C / V conversion module amplifies and converts the weak capacitance signal to a high-frequency voltage signal;

[0036] The high-pass filter and amplifier module filters low-frequency noise in the high-frequency voltage signal, filters low-frequency noise in the high-frequency voltage signal, and amplifies the filtered high-frequency voltage signal to obtain a filtered and amplified high-frequency voltage signal;

[0037] The demodulation module demodulates the filtered high-frequency voltage signal to obtain a low-frequency voltage signal;

[0038] The phase compensation module corrects the phase information in the demodulated signal to further improve the signal accuracy containing the electrode gap information;

[0039] The low-pass filter and amplifier module filters and amplifies high-frequency noise in the low-frequency voltage signal to obtain a voltage signal with high signal-to-noise ratio and containing electrode gap information;

[0040] In the voltage signal containing electrode gap information, when the MEMS structure is in a dynamic state, the electrode gap information comes from the capacitance change caused by the displacement of the moving structure; when the MEMS structure is in a static state, the electrode gap information comes from the capacitance change caused by the capacitance adjustment of the adjustable capacitor.

[0041] In one embodiment, the process of step 3 is specifically:

[0042] According to the input driving voltage size and structure size parameters, the driving force is calculated;

[0043] According to a dynamic equation of the MEMS structure to be measured, a displacement variation of a moving part of the MEMS structure under the driving force is obtained, or a system displacement variation calculated according to a structure area and a capacitance variation of the adjustable capacitor is obtained;

[0044] Since the displacement variation is related to a capacitance gap, and the displacement variation actually reflects an output signal obtained through a signal processing circuit, a mathematical relationship between a voltage signal with high signal-to-noise ratio and containing electrode gap information and the electrode gap can be established based on a capacitance calculation formula;

[0045] Based on the mathematical relationship between the voltage signal with high signal-to-noise ratio and containing electrode gap information and the electrode gap, the electrode gap is accurately calibrated by using known structure and circuit parameters.

[0046] Compared with the prior art, the present application has the following beneficial technical effects:

[0047] 1. The present application proposes to use the adjustable capacitor in the electrode gap measurement, and the combination of the adjustable capacitor and the MEMS structure to be measured can be regarded as a variable capacitor. When the electrode gap of the dynamic MEMS structure is measured, the MEMS structure to be measured can be regarded as a movable electrode plate, and the adjustable capacitor can be regarded as a fixed electrode plate. When the electrode gap of the static MEMS structure is measured, the MEMS structure to be measured can be regarded as a fixed electrode plate, and the adjustable capacitor can be regarded as a movable electrode plate. Therefore, the measurement signal generation unit is always in a dynamic and amplified state during the test. The dynamic and static free conversion measurement method can be used to measure the electrode gap of the MEMS structure in different states by using a set of system and a method, and the application range of the electrode measurement system and method is widened. The weak capacitance signal is amplified by using the resonance idea, and the resolution of the system and the method is improved.

[0048] 2. Based on the resonance idea, the MEMS structure to be measured is in a dynamic state or the adjustable capacitor is in a dynamic state. The signal processing circuit is used to output a signal containing only the capacitance variation part of the MEMS structure to be measured or the adjustable capacitor and in a maximum amplitude state. The influence of the parasitic capacitance on the test signal is avoided, and the measurement accuracy is greatly improved.

[0049] 3. The adjustable capacitor can realize zero adjustment and signal amplification of the MEMS structure to be measured. BRIEF DESCRIPTION OF DRAWINGS

[0050] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative labor based on the drawings shown.

[0051] Figure 1 The structural block diagram of the electrode gap measurement system of the capacitive MEMS structure in the embodiment of the present application is shown in the figure.

[0052] Figure 2 The schematic diagram of the electrode gap detection circuit in the embodiment of the present application is shown in the figure.

[0053] The implementation, functional features and advantages of the present application will be further described with reference to the embodiments and the accompanying drawings. DETAILED DESCRIPTION

[0054] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only a part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all the other embodiments obtained by a person of ordinary skill in the art without creative work are within the protection scope of the present application.

[0055] In addition, the technical solutions in the various embodiments of the present application can be combined with each other, but it must be based on the fact that a person of ordinary skill in the art can realize the combination. When the combination of the technical solutions appears to be contradictory or unachievable, it should be considered that the combination of the technical solutions does not exist and is not within the protection scope of the present application.

[0056] As shown in the figure, the electrode gap measurement system of the capacitive MEMS structure disclosed in the embodiment mainly comprises a measurement signal generation unit, a data processing unit and a signal processing circuit. Figure 1 The measurement signal generation unit is used to generate a capacitive signal reflecting the electrode gap information. The signal processing circuit is used to process the capacitive signal generated by the measurement signal generation unit, convert the capacitive signal into an analog voltage signal which is readable and has a high signal-to-noise ratio, and the data processing unit is used to process the data of the analog voltage signal and calculate the electrode gap value.

[0057] The measurement signal generation unit comprises a driving modulation module, a to-be-measured MEMS structure and an adjustable capacitor. The driving modulation module is used to generate a driving voltage containing three different signals of direct current, alternating current and high-frequency carrier, and to make the to-be-measured MEMS structure and the adjustable capacitor generate a capacitive signal and modulate the capacitive signal after the difference between the two is obtained. The capacitance of the adjustable capacitor is adjustable, and the adjustment principle and size of the capacitance of the adjustable capacitor are determined by the to-be-measured MEMS structure. The specific adjustment principle is as follows:

[0058] When the to-be-measured MEMS structure is in a dynamic state, the capacitance of the adjustable capacitor is equal to the static capacitance of the to-be-measured MEMS structure;

[0059] When the MEMS structure under test is in a static state, the capacitance of the adjustable capacitor fluctuates around the static capacitance of the MEMS structure under test.

[0060] The signal processing circuit includes a C / V conversion module, a high-pass filter and amplification module, a demodulation module, a phase compensation module, and a low-pass filter and amplification module. The C / V conversion module amplifies the modulated weak capacitance signal and converts it into a high-frequency voltage signal. The high-pass filter and amplification module filters low-frequency noise from the high-frequency voltage signal and amplifies the filtered high-frequency voltage signal to obtain a filtered and amplified high-frequency voltage signal. The demodulation module demodulates the filtered and amplified high-frequency voltage signal to obtain a low-frequency voltage signal. The phase compensation module corrects the phase information in the low-frequency voltage signal, further improving the signal accuracy containing electrode gap information. The low-pass filter and amplification module filters and amplifies high-frequency noise from the low-frequency voltage signal to obtain a high signal-to-noise ratio voltage signal containing electrode gap information. Specifically, in the voltage signal containing electrode gap information, when the MEMS structure under test is dynamic, the electrode gap information comes from the capacitance change caused by the displacement of the moving structure; when the MEMS structure under test is static, the electrode gap information comes from the capacitance change caused by the adjustment of the adjustable capacitor.

[0061] The data processing unit derives the mathematical relationship between the output signal and the electrode gap based on the dynamic model of the MEMS structure under test. Then, using data processing software, it precisely calibrates the electrode gap using known structural and circuit parameters. The derivation process of the mathematical relationship is as follows: The applied driving force is calculated based on the input driving voltage and structural dimensions; according to the dynamic equation of the MEMS structure under test, the displacement change of the moving part of the MEMS structure under this driving force condition is calculated, or the system displacement change is calculated based on the structural area and the capacitance change of the adjustable capacitor; according to the capacitance calculation formula, this displacement change is related to the capacitor gap, and the actual displacement change reflects the output signal obtained by the signal processing circuit. Therefore, based on the capacitance calculation formula, a high signal-to-noise ratio mathematical relationship between the voltage signal and the electrode gap, containing electrode gap information, can be established.

[0062] The following section provides a further explanation of the capacitive MEMS structure electrode gap measurement system and its corresponding measurement method in this embodiment, using specific examples.

[0063] Taking a typical "electrostatic drive-capacitive sensing" MEMS structure as an example, using Figure 2 The modulation / demodulation electrode gap detection circuit is shown. Figure 2 The capacitor C formed by the MEMS structure under test s and its parasitic capacitance C j and adjustable capacitor C PEach is subject to a driving voltage V s+ and driving voltage V s- A measurement signal containing information about the capacitance gaps of the MEMS structure under test is then generated. The total capacitance of the MEMS structure under test and its parasitic capacitance, along with the capacitance of the adjustable capacitor, are considered as a differential capacitor, with a voltage V... s+ and V s- The differentially modulated capacitance change signal ΔC is modulated by a modulation signal. The capacitance change signal ΔC then enters a charge amplifier-based C / V conversion circuit and is converted into a high-frequency voltage signal V. c After low-frequency noise components are filtered out by a high-pass filter (HPF), the signal is multiplied by a factor of K. H The filtered signal is amplified to improve the signal-to-noise ratio. Then, a carrier signal with the same frequency as the modulation signal is used for multiplication demodulation and phase compensation. The demodulated low-frequency voltage signal is then passed through a low-pass filter (LPF) and a multiplier K. LP The signal is amplified to further filter out high-frequency noise and amplify the target signal, and output a high-precision voltage signal V. cout On the one hand, due to the presence of the adjustable capacitor, the static capacitance of the MEMS structure under test, including the initial capacitance and parasitic capacitance, can be differentially eliminated by the basic capacitance of the adjustable capacitor, so V cout It is the voltage value reflected by the change in the gap of the MEMS structure under test or the change in the capacitance caused by the change in the capacitance of the adjustable capacitor. This capacitance value only reflects the movable capacitance containing the electrode gap information. On the other hand, the modulation and demodulation electrode gap detection circuit amplifies the output signal based on the resonance concept and eliminates the influence of parasitic capacitance, resulting in high measurement accuracy.

[0064] In practical applications, the output voltage V is obtained. cout The relationship with the electrode gap is fundamental to resonant measurements. Taking an electrostatically driven, capacitively sensed MEMS structure as an example, its model can be equivalent to a typical second-order system, and the dynamic equations can be written as:

[0065]

[0066] In the formula, M is the mass of the MEMS structure, and c s It is the damping coefficient, k s It is the elastic coefficient, F c It is the external excitation force on the MEMS structure, and x is the displacement of the MEMS structure under the action of the excitation force.

[0067] In order for the modulation and demodulation circuit to measure the capacitance change generated based on the resonance concept, a driving voltage V is applied to the MEMS structure. s+ At the same time, a matching adjustable capacitor C is set. P And apply driving voltage V s- Then we have:

[0068]

[0069] In the formula, V dc is the DC voltage amplitude, V ac is the AC voltage amplitude, ω s is the system inherent frequency, t is time, E fs sinω fs t is the carrier, E fs is the carrier amplitude, ω fs is the carrier modulation frequency.

[0070] Then the driving force F s of the system is:

[0071]

[0072] In the formula, C is the static capacitance value of the system, ε is the dielectric constant between the parallel plates, A s is the area of the capacitor formed by the MEMS structure, d0 is the electrode gap in the MEMS structure to be measured.

[0073] Then the system capacitance change ΔC is:

[0074]

[0075] In the formula, Δy is the capacitance gap change of the MEMS structure to be measured or the capacitance adjustment of the adjustable capacitor The displacement change value is calculated according to the capacitance calculation formula and A s .

[0076] After C / V conversion amplification, high-pass filtering and amplification, demodulation and phase compensation, and low-pass filtering and amplification of the output voltage V cout :

[0077]

[0078] In the formula, C f is the reference capacitance of the C / V conversion circuit, K H and K LP are the amplification factors of the signal after high-pass and low-pass respectively, is the phase angle with error, is the phase angle correction value.

[0079] Finally, based on the output voltage V cout , the electrode gap of the MEMS structure to be measured is:

[0080]

[0081] Based on the resonance idea, the signal is phase compensated, and the signal detection method for eliminating the influence of the parasitic capacitance through mathematical idea improves the measurement accuracy of the electrode gap of the MEMS structure.

[0082] The above merely describes the preferred embodiments of the present application, and does not limit the patent scope of the present application. Any equivalent structural transformation, direct / indirect application in other related technical fields, or the like, which is made based on the inventive concept of the present application and the content of the specification and drawings, is included in the patent protection scope of the present application.

Claims

1. A capacitive MEMS structure electrode gap measurement system, characterized in that, The application relates to a method for measuring the electrode gap of a MEMS structure, comprising the following steps: a measurement signal generating unit is used to generate a capacitance signal reflecting electrode gap information; a signal processing circuit is used to process the capacitance signal generated by the measurement signal generating unit, and convert the capacitance signal into an analog voltage signal which is readable and has high signal-to-noise ratio; a data processing unit is used to perform data processing on the analog voltage signal, and calculate the electrode gap value; the measurement signal generating unit comprises a driving modulation module, a to-be-measured MEMS structure and an adjustable capacitor; the driving modulation module is used to generate a driving voltage containing three different signals of direct current, alternating current and high-frequency carrier, and make the to-be-measured MEMS structure and the adjustable capacitor generate a capacitance signal through the driving voltage, and modulate the capacitance signal after the two are differentiated; the capacitance size of the adjustable capacitor is adjustable, and the capacitance adjustment principle and size of the adjustable capacitor are determined by the to-be-measured MEMS structure, specifically: when the to-be-measured MEMS structure is in a dynamic state, the capacitance size of the adjustable capacitor is equal to the static capacitance of the to-be-measured MEMS structure; when the to-be-measured MEMS structure is in a static state, the capacitance size of the adjustable capacitor fluctuates above and below the static capacitance of the to-be-measured MEMS structure.

2. The system of claim 1, wherein the system is configured to measure the gap between the electrodes of the capacitive MEMS structure by: the signal processing circuit comprises: a C / V conversion module which is used to amplify and convert the modulated weak capacitance signal into a high-frequency voltage signal; a high-pass filtering and amplifying module which is used to filter low-frequency noise in the high-frequency voltage signal, and amplify the filtered high-frequency voltage signal; a demodulation module which is used to demodulate the filtered high-frequency voltage signal to obtain a low-frequency voltage signal; a phase compensation module which is used to correct the phase information in the demodulated signal, so as to further improve the signal precision of the electrode gap information; a low-pass filtering and amplifying module which is used to filter and amplify high-frequency noise in the low-frequency voltage signal, and obtain a voltage signal with high signal-to-noise ratio and containing electrode gap information; wherein, in the voltage signal containing electrode gap information, when the to-be-measured MEMS structure is in a dynamic state, the electrode gap information comes from the capacitance change amount generated by the displacement of the moving structure; when the to-be-measured MEMS structure is in a static state, the electrode gap information comes from the capacitance change amount generated by the capacitance adjustment of the adjustable capacitor.

3. The system of claim 2, wherein the gap between the electrodes is measured by a capacitance measurement. when the data processing unit performs data processing, the data processing unit is based on the mathematical relationship between the voltage signal with high signal-to-noise ratio and containing electrode gap information and the electrode gap which is derived according to the dynamic model of the to-be-measured MEMS structure, and then the electrode gap is accurately calibrated based on the mathematical relationship and known structure and circuit parameters.

4. The system of claim 3, wherein the system is configured to measure the gap between the electrodes of the capacitive MEMS structure by: the derivation process of the mathematical relationship is as follows: the driving force is calculated according to the input driving voltage size and structure size parameters; the displacement change amount of the moving part of the MEMS structure under the driving force is calculated according to the dynamic equation of the to-be-measured MEMS structure, or the system displacement change amount is calculated according to the area of the MEMS structure and the capacitance change of the adjustable capacitor; Since the displacement variation is related to the electrode gap, and the displacement variation actually reflects the output signal obtained by the signal processing circuit, a mathematical relationship between the high signal-to-noise ratio voltage signal containing the electrode gap information and the electrode gap is established based on the capacitance calculation formula.

5. A method of measuring electrode gap in a capacitive MEMS structure, characterized by, The measurement method comprises the following steps by using the electrode gap measurement system of the capacitive MEMS structure electrode gap measurement system according to any one of claims 1 to 4: Step 1, generating a capacitance signal reflecting electrode gap information based on a measurement signal generation unit, specifically: Generating a driving voltage containing three different signals of direct current, alternating current and high-frequency carrier based on a driving modulation module; The driving voltage is applied to the to-be-measured MEMS structure and the adjustable capacitor respectively, so that the to-be-measured MEMS structure and the adjustable capacitor generate a capacitance signal, and the signal after the difference between the two is modulated; After the driving voltage is applied to the to-be-measured MEMS structure and the adjustable capacitor, the to-be-measured MEMS structure is in a dynamic state and the capacitance value of the adjustable capacitor is equal to the static capacitance value of the MEMS structure, or the to-be-measured MEMS structure is in a static state and the adjustable capacitor is in a dynamic state, wherein the capacitance value of the adjustable capacitor in the dynamic state fluctuates above and below the static capacitance of the to-be-measured MEMS structure; Step 2, processing the capacitance signal generated by the measurement signal generation unit based on a signal processing circuit, and converting the capacitance signal into a readable, high signal-to-noise ratio analog voltage signal; Step 3, data processing of the analog voltage signal based on a data processing unit, and calculating the electrode gap value.

6. The method of claim 5, wherein the method further comprises: The process of step 2 is specifically: Amplifying and converting the modulated weak capacitance signal into a high-frequency voltage signal based on a C / V conversion module; Filtering low-frequency noise in the high-frequency voltage signal based on a high-pass filtering and amplifying module, and amplifying the filtered high-frequency voltage signal to obtain a filtered and amplified high-frequency voltage signal; Demodulating the filtered high-frequency voltage signal based on a demodulation module to obtain a low-frequency voltage signal; Based on the phase compensation module, the phase information in the demodulated signal is corrected to further improve the signal accuracy containing the electrode gap information; Filtering and amplifying the high-frequency noise in the low-frequency voltage signal based on a low-pass filtering and amplifying module to obtain a high signal-to-noise ratio voltage signal containing electrode gap information; Wherein, in the voltage signal containing electrode gap information, when the to-be-measured MEMS structure is in a dynamic state, the electrode gap information comes from the capacitance variation caused by the displacement of the moving structure; When the to-be-measured MEMS structure is in a static state, the electrode gap information comes from the capacitance variation caused by the capacitance adjustment of the adjustable capacitor.

7. The method of claim 6, wherein the method further comprises: The process of step 3 is specifically: According to the input driving voltage size and structure size parameters, the driving force is calculated; According to the dynamics equation of the to-be-measured MEMS structure, the displacement variation of the moving part of the MEMS structure under the driving force is calculated, or the system displacement variation is calculated according to the structure area and the capacitance variation of the adjustable capacitor; Since the displacement variation is related to the capacitance gap, and the displacement variation actually reflects the output signal obtained by the signal processing circuit, a mathematical relationship between the high signal-to-noise ratio voltage signal containing the electrode gap information and the electrode gap is established based on a capacitance calculation formula; Based on the mathematical relationship between the high signal-to-noise ratio voltage signal containing the electrode gap information and the electrode gap, the electrode gap is accurately calibrated by using known structure and circuit parameters.

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