Capacitive displacement sensor

Abstract

The application provides a kind of capacitive displacement sensor, capacitive displacement sensor includes master control system, measured capacitance, gain charge amplification module and post-processing module;Master frequency controller is used to output first carrier excitation signal and second carrier excitation signal;Gain charge amplification module is used to convert charge into voltage by two-stage low-noise operational amplifier, and output differential carrier signal;Post-processing module is used to mix the target carrier signal corresponding to the differential carrier signal and the reference carrier signal, remove the high frequency and frequency multiplication components in the mixed signal, and obtain the direct current signal;Master control system is used to call calibration parameters, and the direct current signal is converted by using calibration parameters to obtain actual displacement. By using the capacitive displacement sensor, the problem of weak anti-interference, long line transmission, difficult to adapt to the complex wiring of semiconductor equipment, strong electromagnetic interference and high-precision stable measurement requirement of existing capacitive displacement sensor is solved.

Description

Technical Field

[0001] This application relates to the field of sensor technology, and more specifically, to a capacitive displacement sensor. Background Technology

[0002] Capacitive displacement sensors are widely used in high-precision measurement scenarios such as semiconductor precision processing equipment and micro-nano positioning platforms due to their advantages such as non-contact measurement, high resolution, simple structure and fast response speed.

[0003] Traditional capacitive displacement sensor solutions measure displacement by connecting the equivalent capacitance of the displacement model to the two ends of an operational amplifier, making the displacement proportional to the capacitance. However, existing capacitive displacement sensors cannot transmit over long distances and are highly susceptible to interference from the surrounding environment and electromagnetic fields. They are ill-suited for applications requiring complex wiring, strong electromagnetic interference, and high-precision, stable measurement in semiconductor equipment. Summary of the Invention

[0004] In view of this, the purpose of this application is to provide a capacitive displacement sensor to overcome at least one of the above-mentioned defects.

[0005] In a first aspect, embodiments of this application provide a capacitive displacement sensor, which includes a main control system, a capacitor under test, a gain charge amplification module, and a post-processing module. The main control system has a built-in main control frequency controller, and the capacitor under test is connected to the input terminal of the gain charge amplification module to establish an inverse proportional relationship between the output electrical signal and the plate displacement. The main frequency controller is used to output a first carrier excitation signal and a second carrier excitation signal. The first carrier excitation signal is applied to the test surface of the capacitor under test to modulate the displacement information of the test surface onto the first carrier excitation signal. The second carrier excitation signal is sent to the post-processing module as a reference carrier signal. The gain charge amplifier module is used to collect the charge of the capacitor under test, convert the charge into voltage through a two-stage low-noise operational amplifier, and output a differential carrier signal carrying displacement information. The post-processing module, connected to the gain charge amplifier module, is used to perform frequency mixing processing on the target carrier signal and the reference carrier signal corresponding to the differential carrier signal, and remove the high-frequency and harmonic components in the mixed signal to obtain a DC signal; The main control system is also used to retrieve calibration parameters and use these parameters to convert and process the DC signal to obtain the actual displacement.

[0006] In an optional implementation, the gain charge amplification module is a two-stage low-noise charge amplifier, comprising a first-stage charge integrating operational amplifier, a second-stage bias compensation operational amplifier, and a differential drive operational amplifier. The first-stage charge integrating operational amplifier is used to acquire the charge of the capacitor under test and convert the acquired charge into an AC carrier signal carrying displacement information. The second-stage bias compensation operational amplifier is connected to the output of the first-stage charge integrating operational amplifier and is used to suppress DC bias and voltage fluctuations in the AC carrier signal. The differential drive operational amplifier is connected to the output of the second-stage bias compensation operational amplifier and is used to receive the single-ended AC carrier signal output by the second-stage bias compensation operational amplifier and convert the single-ended AC carrier signal into a differential carrier signal.

[0007] In an optional implementation, the post-processing module further includes a first digital filter, a carrier demodulation unit, and a second digital filter; the first digital filter is used to perform frequency-selective noise reduction processing on the carrier digital signal; the carrier demodulation unit is connected to the output of the first digital filter and is used to perform frequency mixing processing on the target carrier signal and the reference carrier signal, outputting a mixed signal including a displacement DC component and a harmonic component; the second digital filter is connected to the output of the carrier demodulation unit and is used to filter out high-frequency and harmonic components from the mixed signal and extract a DC signal inversely proportional to the displacement.

[0008] In an optional implementation, the actual displacement refers to the distance between the plates of the measured surface and the common fixed electrode. The actual displacement is the product of the first ratio, the area of ​​the common electrode, the dielectric constant, and the second ratio. The first ratio is the ratio of the input voltage of the measured surface to the output voltage amplitude of the gain charge amplification module, and the second ratio is the ratio of the preset value to the gain adjustment capacitor value in the gain charge amplification module.

[0009] In an optional implementation, the capacitive displacement sensor further includes a single-ended to differential conversion module and an analog calculation module; the single-ended to differential conversion module is connected to the output of the gain charge amplification module and is used to perform secondary differential shaping on the differential carrier signal to make it suitable for long-distance transmission in semiconductor devices; the analog calculation module is connected to the output of the single-ended to differential conversion module and is used to preprocess the differential carrier signal to eliminate the mismatch error between the two differential signals.

[0010] In an optional implementation, the post-processing module further includes a linear correction unit for linearly correcting the DC signal to output a linearly corrected DC signal.

[0011] In an optional implementation, the capacitive displacement sensor further includes an adjustable filtering module, which is disposed between the capacitor under test and the gain charge amplification module to filter out low-frequency jitter interference in the device's microenvironment and retain only the effective carrier wave.

[0012] In an optional implementation, the capacitive displacement sensor further includes a calibration module, which is used to acquire the actual displacement, the capacitance to be measured corresponding to the actual displacement, and the DC signal, and generate calibration parameters.

[0013] In an optional implementation, the first carrier excitation signal and the second carrier excitation signal are carrier excitation signals that are from the same source, have the same frequency, and are frequency-adjustable.

[0014] In an optional implementation, the post-processing module further includes a differential-to-single-ended unit and an analog-to-digital conversion unit; the differential-to-single-ended unit is used to restore the differential carrier signal after analog calculation to a single-ended signal; the analog-to-digital conversion unit is connected to the output of the differential-to-single-ended unit and is used to sample the single-ended signal to obtain a carrier digital signal.

[0015] The embodiments of this application bring the following beneficial effects: This application provides a capacitive displacement sensor, including a main control system, a capacitor under test, a gain-charge amplification module, and a post-processing module. The main control system has a built-in main control frequency controller. The capacitor under test is connected to the input terminal of the gain-charge amplification module to establish an inverse proportional relationship between the output electrical signal and the plate displacement. The main control frequency controller is used to output a first carrier excitation signal and a second carrier excitation signal. The first carrier excitation signal is applied to the measured surface of the capacitor under test to modulate the displacement information of the measured surface onto the first carrier excitation signal. The second carrier excitation signal is sent to the post-processing module as a reference carrier signal. The gain-charge amplification module is used to collect the charge of the capacitor under test, convert the charge into voltage through a two-stage low-noise operational amplifier, and output a differential carrier signal carrying displacement information. The post-processing module is connected to the gain-charge amplification module and is used to perform frequency mixing processing on the target carrier signal and the reference carrier signal corresponding to the differential carrier signal, and remove high-frequency and harmonic components from the mixed signal to obtain a DC signal. The main control system is also used to retrieve calibration parameters and use the calibration parameters to perform conversion processing on the DC signal to obtain the actual displacement.

[0016] By employing a two-stage charge amplification architecture combined with carrier synchronous demodulation, signal DC bias and low-frequency noise can be effectively suppressed, supporting long-distance differential transmission. At the same time, through hardware and software collaborative correction and compensation of the inherent nonlinear errors of capacitance and displacement, the accuracy, stability and anti-interference capability of micro-gap displacement measurement of semiconductor equipment are greatly improved. Compared with the existing capacitive displacement sensor methods, it solves the problems of weak anti-interference, inability to transmit over long distances, and difficulty in adapting to the use requirements of complex wiring, strong electromagnetic interference and high-precision and stable measurement of semiconductor equipment.

[0017] To make the above-mentioned objectives, features and advantages of this application more apparent and understandable, preferred embodiments are described below in detail with reference to the accompanying drawings. Attached Figure Description

[0018] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of this application and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A schematic diagram of the structure of the capacitive displacement sensor provided in an embodiment of this application is shown; Figure 2 A circuit diagram of the gain charge amplification module provided in an embodiment of this application is shown; Figure 3 A simulation diagram of the gain charge amplification module provided in the embodiment of this application is shown; Figure 4 A simulation diagram of the gain charge amplification module of the prior art is shown. Detailed Implementation

[0020] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely represents selected embodiments of this application. Based on the embodiments of this application, every other embodiment obtained by those skilled in the art without inventive effort falls within the scope of protection of this application.

[0021] Please see Figure 1 , Figure 1 This is a schematic diagram of the structure of the capacitive displacement sensor provided in an embodiment of this application. Figure 1 As shown, the capacitive displacement sensor provided in this embodiment includes a main control system 100 and a capacitor to be measured. The system includes a calibration module 200, an adjustable filter module 300, a gain and charge amplification module 400, a single-ended to differential converter module 500, an analog calculation module 600, and a post-processing module 700.

[0022] The main control system 100 is the central control and processing unit for the entire excitation demodulation capacitive displacement sensor. It integrates a main control frequency controller, which generates a 22kHz, 39Vpp carrier excitation signal via a digital-to-analog converter (DAC) and outputs it in two paths: a first carrier excitation signal and a second carrier excitation signal. The first carrier excitation signal is then applied to the capacitor under test. The displacement information of the measured surface is modulated onto the first carrier excitation signal, and the second carrier excitation signal is sent to the post-processing module 700 as a reference carrier signal. The first and second carrier excitation signals are carrier excitation signals of the same origin and frequency, and their frequencies are adjustable.

[0023] The adjustable filter module 300 is set on the capacitor under test. Between the gain and charge amplification module 400, it is used to filter out low-frequency jitter interference in the device's microenvironment, retaining only the effective carrier wave.

[0024] Capacitor under test The signal is connected to the input terminal of the gain charge amplifier module 400 via the adjustable filter module 300 to establish an inverse proportional relationship between the output electrical signal and the plate displacement.

[0025] The gain charge amplifier module 400 is used to collect the charge of the capacitor under test, convert the charge into voltage through a two-stage low-noise operational amplifier, and output a differential carrier signal carrying displacement information.

[0026] The input terminal of the single-ended to differential module 500 is connected to the output terminal of the gain charge amplifier module 400. The single-ended to differential module 500 is used to perform secondary differential shaping on the differential carrier signal output by the gain charge amplifier module 400 to make it suitable for long-distance transmission of semiconductor devices.

[0027] The input of the analog calculation module 600 is connected to the output of the single-ended to differential module 500. The analog calculation module 600 is used to preprocess the differential carrier signal after double differential shaping to eliminate the mismatch error between the two differential signals. The preprocessing includes impedance matching, amplitude equalization, and pre-amplification conditioning to eliminate the amplitude and phase mismatch error between the two differential signals and ensure the symmetry of the two signals.

[0028] The input terminal of the post-processing module 700 is connected to the output terminal of the analog calculation module 600. The post-processing module 700 is used to perform frequency mixing processing on the target carrier signal and the reference carrier signal corresponding to the differential carrier signal, and remove the high-frequency and harmonic components in the mixed signal to obtain a DC signal.

[0029] The post-processing module 700 includes a differential-to-single-ended unit 710, an analog-to-digital conversion unit 720, a first digital filter 730, a carrier demodulation unit 740, a second digital filter 750, and a linear correction unit 760.

[0030] The input terminal of the differential-to-single-ended unit 710 is connected to the output terminal of the analog calculation module 600. The differential-to-single-ended unit 710 is used to restore the differential carrier signal after analog calculation to a single-ended signal in order to extract the effective differential signal and suppress common-mode noise.

[0031] The input terminal of the analog-to-digital converter 720 is connected to the output terminal of the differential-to-single-ended converter 710, and is used to perform high-precision sampling of the 22kHz single-ended signal to obtain the carrier digital signal, so as to convert the continuous analog voltage into a discrete digital signal.

[0032] The input of the first digital filter 730 is connected to the output of the analog-to-digital converter 720. The first digital filter 730 is used to perform frequency selection and noise reduction processing on the carrier digital signal. The first digital filter 730 is a digital bandpass filter unit that performs secondary fine frequency selection processing on the sampled digital signal. It accurately retains only the 22kHz target carrier digital signal, filters out aliasing noise introduced by ADC sampling, residual low-frequency jitter from the equipment, power frequency interference, and spurious frequencies such as pulse spikes, and outputs the purified carrier digital signal to the carrier demodulation unit 740 to avoid various noises from participating in the mixing operation and causing demodulation errors, thus ensuring synchronous demodulation accuracy.

[0033] The input terminal of the carrier demodulation unit 740 is connected to the output terminal of the first digital filter 730. The carrier demodulation unit 740 is used to perform frequency mixing processing on the target carrier signal and the reference carrier signal corresponding to the differential carrier signal, multiply and mix the two carrier signals, and output a mixed signal including the displacement DC component and the harmonic component. The mixed signal is then output to the second digital filter 750 to extract the DC digital quantity characterizing the plate displacement by filtering out the harmonic high-frequency component, providing a basic signal for subsequent displacement conversion and correction.

[0034] The input of the second digital filter 750 is connected to the output of the carrier demodulation unit 740. The second digital filter 750 is a digital low-pass filter unit used to filter out high-frequency and harmonic components from the mixed signal, retain the DC digital quantity related to the displacement of the plate to be measured, so as to extract the DC signal that is inversely proportional to the displacement, and output the purified DC digital signal to the linear correction unit 760 to eliminate the interference of harmonic components on displacement conversion and ensure the accuracy of subsequent displacement correction and calculation.

[0035] The input of the linear correction unit 760 is connected to the output of the second digital filter 750, and is used to perform linear correction on the DC signal to output a linearly corrected DC signal. The linear correction unit is a data processing unit located between the second digital filter 750 and the main control system 100. The linear correction unit 760 receives the DC digital quantity related to the distance between the plates under test output by the second digital filter. Taking into account the inherent inverse proportional nonlinear relationship between capacitance and displacement of parallel plate capacitance, and combining the calibration parameters such as zero point, temperature drift, parasitic capacitance, and plate edge effect pre-stored in the calibration module, it eliminates the full-range nonlinear error through inverse proportional conversion, piecewise fitting correction, and multi-dimensional error compensation calculation. It outputs the corrected high-precision displacement data and transmits it to the main control system 100, providing the corrected basic data for the main control system 100 to output the actual displacement value.

[0036] The main control system 100 is connected to the linear correction unit 760. The main control system 100 retrieves calibration parameters from the calibration module 200 and uses these parameters to convert and process the DC signal to obtain the actual displacement. At this time, the main control system 100 receives the DC digital output from the linear correction unit 760, retrieves the calibration parameters such as zero point, temperature drift, and parasitic capacitance pre-stored in the calibration module 200, and sequentially completes the inverse proportional conversion between capacitance and displacement, full-range nonlinear segmental correction, and multi-dimensional error compensation. It calculates the actual displacement between the measured target surface and the common fixed electrode, stores the calibration parameters and measurement data, and outputs the actual displacement value through the communication interface to achieve closed-loop control of the equipment.

[0037] The calibration module 200 is connected to the main control system 100 and the gain charge amplifier module 400. The calibration module 200 is used to collect the actual displacement, the capacitance to be measured corresponding to the actual displacement, and the DC signal to generate calibration parameters.

[0038] In one embodiment, the gain charge amplification module is a two-stage low-noise charge amplifier, which includes a first-stage charge integration operational amplifier, a second-stage bias compensation operational amplifier, and a differential drive operational amplifier.

[0039] The following reference Figure 2 Let's introduce the gain charge amplification module.

[0040] Figure 2 The circuit diagram of the gain charge amplification module provided in the embodiment of this application is shown, as follows: Figure 2As shown, the gain charge amplification module includes a first-stage charge integrating operational amplifier U1, a second-stage bias compensation operational amplifier U2, a differential drive operational amplifier U3, a first inductor L1, a second inductor L2 (common-mode inductor), a second resistor R2, a fourth resistor R4, a fifth resistor R5, a sixth resistor R6, a ninth resistor R9, a tenth resistor R10, a first capacitor C1, a second capacitor C2, a third capacitor C3, a fifth capacitor C5, a sixth capacitor C6, a seventh capacitor C7, an eighth capacitor C8, a tenth capacitor C10, and an eleventh capacitor C11. The adjustable filter module is not shown in the diagram.

[0041] P5_PRB represents the positive input voltage, and N5_PRB represents the negative input voltage. VoutF represents the positive differential output terminal, and VoutN represents the inverting differential output terminal. Through the positive and inverting differential output terminals, the gain charge amplifier module outputs a 22kHz high-frequency differential AC analog voltage signal whose amplitude changes in real time with the displacement of the object being measured. DIAG represents a calibration charge signal with known amplitude and frequency output from the main control system.

[0042] The second capacitor C2 is the feedback integration reference capacitor, i.e., the gain adjustment capacitor, of the first-stage charge integrating operational amplifier U1. It is used to integrate and acquire the induced charge output by the capacitor under test, determine the conversion gain of the charge amplifier circuit, and realize the standardized conversion from sensed charge to AC carrier voltage. Since the charge generated by displacement changes is attached to the excitation carrier, the charge-to-voltage conversion gain can be changed by the second capacitor C2 to adjust the output amplitude of the carrier signal, thereby realizing the amplitude adjustment of displacement information in the excitation signal.

[0043] The gain charge amplification module is connected to the calibration module through a first RC filter circuit consisting of a second inductor L2, a first resistor R1, a third resistor R3, and a fourth capacitor C4. Simultaneously, the gain charge amplification module is connected to the capacitor under test through a second RC filter circuit consisting of a seventh resistor R7, an eighth resistor R8, and a ninth capacitor C9. This second RC filter circuit is used to filter out high-frequency noise and improve the signal-to-noise ratio.

[0044] The first-stage charge integrating operational amplifier U1 is used to acquire the charge of the capacitor under test and convert the acquired charge into an AC carrier signal carrying displacement information.

[0045] The second-stage bias compensation operational amplifier U2 is connected to the output of the first-stage charge integration operational amplifier U1. It is used to further amplify and filter the AC carrier signal output by U1, and suppress DC bias and voltage fluctuations in the AC carrier signal.

[0046] The differential driver operational amplifier U3 is connected to the output of the second-stage bias compensation operational amplifier. It receives the single-ended AC carrier signal output from the second-stage bias compensation operational amplifier and converts it into a low-noise differential carrier signal. The differential driver operational amplifier U3 has differential inputs (pins 1 and 8) and differential outputs (pins 4 and 5), which can effectively suppress common-mode interference. Pin 2 (VOCM) is used to set the output common-mode voltage to ensure that the output signal is within the ADC input range.

[0047] In one embodiment, the actual displacement d refers to the distance between the plates of the measured surface and the common fixed electrode. The actual displacement d is the product of the first ratio, the area of ​​the common electrode, the dielectric constant, and the second ratio.

[0048] The first ratio is the ratio of the input voltage of the measured surface to the output voltage amplitude of the gain charge amplification module, and the second ratio is the ratio of the preset value to the gain adjustment capacitor value in the gain charge amplification module.

[0049] The area of ​​the common electrode is denoted as: The dielectric constant is denoted as: The input voltage of the measured surface is denoted as: The output voltage amplitude of the gain charge amplifier module is denoted as: The preset value is 1, and the gain adjustment capacitor value (the capacitance value of the second capacitor) is denoted as: Then we have: .

[0050] In one embodiment, the second carrier excitation signal (reference carrier signal) can be expressed as: The differential carrier signal output by the gain charge amplifier module 400 is amplified, transmitted, analog conditioned, and sampled by an ADC to obtain the target carrier signal. The target carrier signal is the input signal of the carrier demodulation unit and can be expressed as: .

[0051] After the second carrier excitation signal and the target carrier signal are mixed by the carrier demodulation unit, the mixed signal can be expressed as: Where D represents the amplitude of the second carrier excitation signal (reference carrier signal) output by the main control system.

[0052] After passing through the second digital filter, the high-frequency and harmonic components in the mixed signal are filtered out, retaining the DC digital quantity related to the measured displacement of the electrode plate. This allows the extraction of a DC signal inversely proportional to the displacement. At this point, the DC signal is represented as: The DC signal is corrected by a linear correction unit to eliminate nonlinear errors before being input into the main control system.

[0053] The following reference Figure 3 , Figure 4 This paper will introduce the beneficial effects of the gain charge amplification module provided in the embodiments of this application.

[0054] Figure 3 The simulation effect diagram of the gain charge amplification module provided in the embodiment of this application is shown, as follows: Figure 3 As shown, the gain charge amplifier module provided in this embodiment of the application uses a bipolar charge amplifier with an input signal of ±4.8mV, an output signal of ±3.6V, a magnification of 750, and a gain of 58dB.

[0055] Figure 4 The simulation results of a prior art gain-charge amplification module are shown, such as... Figure 4 As shown, the existing gain charge amplifier module uses a unipolar charge amplifier with an input signal of ±29.5mV, an output signal of ±3.6V, a gain of 122, and a gain of 41.7dB.

[0056] As can be seen, this application achieves higher sensitivity by employing a bipolar charge amplifier scheme. Under the same circuit configuration, the amplification factor of the bipolar charge amplifier (750 times) is much higher than that of the unipolar charge amplifier (122 times), indicating that it has a stronger amplification capability for weak input charge signals and is more suitable for measuring extremely small capacitance changes.

[0057] Meanwhile, the bipolar scheme offers superior noise suppression. The bipolar structure, through differential signal amplification, naturally suppresses common-mode noise and temperature drift, thus allowing stable operation with lower input signals (e.g., ±4.8mV). In contrast, the unipolar scheme requires a higher input signal (±29.5mV) to achieve the same output voltage. Furthermore, the output signal of this embodiment and the prior art both reach ±3.6V, indicating that the circuit design goals are consistent; the bipolar scheme achieves this goal with higher gain, while the unipolar scheme requires a larger input excitation to achieve the same output.

[0058] The capacitive displacement sensor provided in this application has the following technical advantages: First, it adopts a two-stage low-noise charge amplification architecture, coupled with differential drive to output differential carrier signals, resulting in stronger common-mode rejection capability and enabling stable long-distance signal transmission in complex wiring scenarios of semiconductor equipment. Compared with traditional single-stage amplification structures, the embodiment of this application can achieve a gain of up to 58dB, significantly improving the sensitivity to amplify weak charge signals and accurately capturing minute changes in plate capacitance.

[0059] Secondly, the main frequency controller outputs dual-channel carrier excitation signals of the same source and frequency. One channel modulates the displacement information, and the other serves as a demodulation reference signal. Synchronous coherent mixing can accurately separate the DC component of the displacement and filter out carrier frequency doubling interference. The carrier frequency and phase remain stable and distortion-free throughout the entire process, avoiding the introduction of measurement errors by clutter in demodulation and ensuring the calculation accuracy of the demodulation stage.

[0060] Third, the calibration module can collect multiple sets of displacement, capacitance, and output signal data to generate complete calibration parameters, providing the main control system and linear correction unit with a basis for zero-point, temperature drift, parasitic capacitance, and edge effect compensation. Through inverse proportional conversion and piecewise linear correction, it offsets the inherent nonlinearity of capacitance-displacement, achieving high-precision displacement calculation output across the entire range.

[0061] Fourth, the gain charge amplification module incorporates a second-stage bias compensation operational amplifier, which effectively suppresses the DC bias and voltage drift generated by the first-stage integrating operational amplifier, reducing charge accumulation and saturation issues. Simultaneously, it is paired with a calibration module to inject a standard charge signal to complete the overall gain self-test calibration, reducing long-term measurement deviations caused by component dispersion and temperature / humidity variations.

[0062] Fifth, a single-ended to differential conversion module and an analog calculation module are added, which can perform secondary shaping of the differential signal and equalize the amplitude and phase of the two signals, eliminating differential channel mismatch errors. The back-end differential to single-ended unit, together with high-precision ADC sampling, takes into account both the anti-interference requirements of long-distance transmission and the needs of digital signal acquisition, and is suitable for long-term online monitoring of semiconductor precision micro-gap.

[0063] Those skilled in the art will clearly understand that, for the sake of convenience and brevity, the specific working processes of the systems, devices, and units described above can be referred to the corresponding processes in the foregoing method embodiments, and will not be repeated here.

[0064] In the several embodiments provided in this application, it should be understood that the disclosed systems, apparatuses, and methods can be implemented in other ways. The apparatus embodiments described above are merely illustrative. For example, the division of units is only a logical functional division, and in actual implementation, there may be other division methods. Furthermore, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Additionally, the shown or discussed mutual couplings, direct couplings, or communication connections may be through some communication interfaces; indirect couplings or communication connections between devices or units may be electrical, mechanical, or other forms.

[0065] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0066] In addition, the functional units in the various embodiments of this application can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0067] If the aforementioned functions are implemented as software functional units and sold or used as independent products, they can be stored in a processor-executable, non-volatile, computer-readable storage medium. Based on this understanding, the technical solution of this application, in essence, or the part that contributes to the prior art, or a portion of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods described in the various embodiments of this application. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0068] Finally, it should be noted that the above-described embodiments are merely specific implementations of this application, used to illustrate the technical solutions of this application, and not to limit them. The scope of protection of this application is not limited thereto. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that any person skilled in the art can still modify or easily conceive of changes to the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features, within the scope of the technology disclosed in this application. Such modifications, changes, or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be covered within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the scope of the claims.

Claims

1. A capacitive displacement sensor, characterized in that, The capacitive displacement sensor includes a main control system, a capacitor under test, a gain charge amplification module, and a post-processing module. The main control system has a built-in main control frequency controller. The capacitor under test is connected to the input terminal of the gain charge amplification module to establish an inverse proportional relationship between the output electrical signal and the plate displacement. The main control frequency controller is used to output a first carrier excitation signal and a second carrier excitation signal. The first carrier excitation signal is applied to the test surface of the capacitor under test so as to modulate the displacement information of the test surface onto the first carrier excitation signal. The second carrier excitation signal is sent to the post-processing module as a reference carrier signal. The gain charge amplification module is used to collect the charge of the capacitor under test, convert the charge into voltage through a two-stage low-noise operational amplifier, and output a differential carrier signal carrying the displacement information. The post-processing module is connected to the gain charge amplification module and is used to perform frequency mixing processing on the target carrier signal corresponding to the differential carrier signal and the reference carrier signal, and remove the high-frequency and harmonic components in the mixed signal to obtain a DC signal. The main control system is also used to retrieve calibration parameters and use the calibration parameters to perform conversion processing on the DC signal to obtain the actual displacement.

2. The capacitive displacement sensor according to claim 1, characterized in that, The gain charge amplifier module is a two-stage low-noise charge amplifier, which includes a first-stage charge integration operational amplifier, a second-stage bias compensation operational amplifier, and a differential drive operational amplifier. The first-stage charge integrating operational amplifier is used to collect the charge of the capacitor under test and convert the collected charge into an AC carrier signal carrying the displacement information; The second-stage bias compensation operational amplifier is connected to the output terminal of the first-stage charge integration operational amplifier and is used to suppress DC bias and voltage fluctuations in the AC carrier signal. The differential drive operational amplifier is connected to the output terminal of the second-stage bias compensation operational amplifier and is used to receive the single-ended AC carrier signal output by the second-stage bias compensation operational amplifier and convert the single-ended AC carrier signal into a differential carrier signal.

3. The capacitive displacement sensor according to claim 1, characterized in that, The post-processing module further includes a first digital filter, a carrier demodulation unit, and a second digital filter; The first digital filter is used to perform frequency-selective noise reduction processing on the carrier digital signal; The carrier demodulation unit is connected to the output of the first digital filter and is used to perform frequency mixing processing on the target carrier signal and the reference carrier signal, and output a mixed signal including a displacement DC component and a harmonic component. The second digital filter is connected to the output of the carrier demodulation unit and is used to filter out high-frequency and harmonic components from the mixed signal and extract a DC signal that is inversely proportional to the displacement.

4. The capacitive displacement sensor according to claim 1, characterized in that, The actual displacement refers to the distance between the plates of the measured surface and the common fixed electrode. The actual displacement is the product of the first ratio, the area of ​​the common electrode, the dielectric constant, and the second ratio. The first ratio is the ratio of the input voltage of the measured surface to the output voltage amplitude of the gain charge amplification module, and the second ratio is the ratio of a preset value to the gain adjustment capacitor value in the gain charge amplification module.

5. The capacitive displacement sensor according to claim 1, characterized in that, The capacitive displacement sensor also includes a single-ended to differential module and an analog calculation module; The single-ended to differential module is connected to the output of the gain charge amplifier module and is used to perform secondary differential shaping on the differential carrier signal to make it suitable for long-distance transmission in semiconductor devices. The simulation solution module is connected to the output of the single-ended to differential module and is used to preprocess the differential carrier signal to eliminate the mismatch error between the two differential signals.

6. The capacitive displacement sensor according to claim 1, characterized in that, The post-processing module further includes a linear correction unit, which is used to perform linear correction on the DC signal to output a linearly corrected DC signal.

7. The capacitive displacement sensor according to claim 1, characterized in that, The capacitive displacement sensor also includes an adjustable filtering module, which is located between the capacitor under test and the gain charge amplification module. The adjustable filtering module is used to filter out low-frequency jitter interference in the micro-environment of the equipment and retain only the effective carrier wave.

8. The capacitive displacement sensor according to claim 1, characterized in that, The capacitive displacement sensor also includes a calibration module, which is used to collect the actual displacement, the capacitance to be measured corresponding to the actual displacement, and the DC signal to generate calibration parameters.

9. The capacitive displacement sensor according to claim 1, characterized in that, The first carrier excitation signal and the second carrier excitation signal are carrier excitation signals of the same origin and frequency and whose frequency is adjustable.

10. The capacitive displacement sensor according to claim 5, characterized in that, The post-processing module also includes a differential-to-single-ended conversion unit and an analog-to-digital conversion unit; The differential-to-single-ended unit is used to restore the differential carrier signal after the analog calculation to a single-ended signal; The analog-to-digital conversion unit is connected to the output of the differential-to-single-ended unit and is used to sample the single-ended signal to obtain a carrier digital signal.

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