A method for calibrating a wide-spectrum snapshot ellipsometer

Abstract

The present application belongs to the technical field related to optical measurement, and specifically discloses a method for calibrating a wide-spectrum snapshot ellipsometer. The present application first divides the process of adjustment into multiple modulation states; the preliminary modulation state is the state of relative zero degree between polarization elements, the final modulation state is the state during measurement, and the intermediate multi-step modulation states are multiple intermediate states from the preliminary modulation state to the final modulation state in sequence; the channel distribution of the theoretical spectrum signal of the ellipsometer under each modulation state is derived; then the ellipsometer is gradually adjusted according to each modulation state, so that the channel distribution of the actual spectrum signal under each modulation state is closest to the channel distribution of the corresponding theoretical spectrum signal; different channels are intercepted from the channel distribution of the actual spectrum signal, and the phase delay of each wave plate is obtained by combining after inverse Fourier transformation to complete the calibration of the ellipsometer. The adjustment and calibration method of the present application does not require additional adjustment and calibration instruments, and the adjustment and calibration process is quick and convenient, and the accuracy is higher.

Description

Technical Field

[0001] The present application belongs to the technical field related to optical measurement, and more specifically, relates to an assembly and calibration method for a wide-spectrum snapshot ellipsometer. Background Art

[0002] With the continuous improvement of manufacturing processes and the continuous reduction of semiconductor manufacturing technology nodes, IC devices are facing severe challenges brought about by the development trend of miniaturization, portability, high speed, and low power consumption. In the semiconductor manufacturing process, the thickness and optical parameters of thin films are important factors affecting device performance. Ellipsometry has become the de facto standard technology for measuring thin film parameters. Wide-spectrum snapshot ellipsometers have broad application prospects due to their lack of moving parts, compact size, and combination of measurement speed and accuracy. The basis for ensuring its measurement accuracy is the precise installation and calibration of optical components at specific azimuth angles. Therefore, it is necessary to develop a technical method for quickly and accurately assembling and calibrating wide-spectrum snapshot ellipsometers.

[0003] At present, the optical elements involved in the installation angle of the wide-spectrum snapshot ellipsometer include polarizers and multi-order wave plates. Their installation relies on a lens mounting frame with a differential head, and the azimuth angle of the element is adjusted by the scale line of the mounting frame; or an additional instrument such as a polarimeter is used to measure and adjust the installation angle of the element. In summary, the following problems exist in the installation process: (1) The optical axis angle of the optical element is difficult to align with the scale line; (2) It is difficult to ensure the accuracy of the azimuth adjustment by observing the scale line; (3) The mounting frame with a differential head is large in size, which makes it difficult to take advantage of the compact size of the wide-spectrum snapshot ellipsometer; (4) The high cost of additional instruments such as high-precision mounting frames and polarimeter is not conducive to mass production. The calibration of the wide-spectrum snapshot ellipsometer is usually carried out after the component installation is completed, and a new standard element or sample is introduced to calibrate the delay of the multi-order wave plate. In summary, the following problems exist in the calibration process: (1) The angular error of the component installation will be transmitted to the calibration process; (2) The parameters of the standard element or sample are required to be precise, and the calibration accuracy is difficult to ensure. Summary of the Invention

[0004] In response to the above defects or improvement needs of the prior art, the present application provides a method for calibrating a wide-spectrum snapshot ellipsometer, which aims to solve the technical problem that the accuracy of the existing calibration method is difficult to ensure.

[0005] To achieve the above objectives, in a first aspect, the present application provides a method for calibrating a wide-spectrum snapshot ellipsometer, comprising:

[0006] The adjustment process is divided into N+1 modulation states; N is the number of wave plates in the ellipsometer, the initial modulation state is the relative zero degree state between the polarization elements, the final modulation state is the state during measurement, and the intermediate N-1 modulation states are the N-1 intermediate states from the initial modulation state to the final modulation state.

[0007] Obtain the channel distribution of the theoretical spectral signal under each modulation state;

[0008] The ellipsometer is adjusted step by step according to the state of each modulation state so that the channel distribution of the actual spectral signal in each modulation state is closest to the channel distribution of the corresponding theoretical spectral signal;

[0009] Different channels are intercepted from the channel distribution of the actual spectral signal, and the phase delay of each wave plate is obtained by combining them after inverse Fourier transformation, thereby completing the calibration of the ellipsometer.

[0010] Preferably, the modulation state is specifically an angle combination of all polarization elements in the ellipsometer; in different modulation states, the ellipsometer modulates in different states to generate polarized light, and demodulates in different states at the same time.

[0011] Preferably, the spectral signal is a signal obtained by uniform sampling of the spectrometer in the wavenumber domain; and the channel distribution is a series of Fourier coefficients in the optical path difference domain obtained by performing Fourier transform on the spectral signal.

[0012] Preferably, the spectral signal Specifically:

[0013]

[0014] in, is the spectral response of the light source, and the modulation effect of the N wave plates in the ellipsometer is coupled to k Different modulation channels, For the k The phase angle of each modulation channel, is the base of natural logarithms, Is an imaginary unit.

[0015] Preferably, the channel distribution Specifically:

[0016]

[0017] in, is the channel distribution of the light source. The modulation effect of N wave plates in the ellipsometer will be coupled as k Different modulation channels, It is k The center frequency of the modulation channel, is the impulse function.

[0018] Preferably, the ellipsometer is gradually adjusted according to the state of each modulation state so that the channel distribution of the actual spectral signal in each modulation state is closest to the channel distribution of the corresponding theoretical spectral signal, specifically:

[0019] The angle of the polarization element in the rotating ellipsometer reaches a state corresponding to the modulation state;

[0020] The angle of the polarization element in the ellipsometer is fine-tuned until the channel distribution of the actual spectral signal output by the ellipsometer is closest to the channel distribution of the theoretical spectral signal under the corresponding modulation state.

[0021] Preferably, different channels are intercepted from the channel distribution of the actual spectral signal, and are combined after inverse Fourier transformation to obtain the phase delay of each wave plate; wherein each wave plate has multiple combinations to obtain the phase delay.

[0022] Preferably, different channels are intercepted from the channel distribution of the actual spectral signal, and the phase delay of each wave plate is obtained by combining them after inverse Fourier transformation; different combinations are selected to obtain the phase delay of the same wave plate, and then the obtained phase delays are averaged to obtain the final phase delay of the wave plate.

[0023] In a second aspect, the present application provides an electronic device comprising: at least one memory for storing programs; and at least one processor for executing the programs stored in the memory. When the program stored in the memory is executed, the processor is used to execute the method described in the first aspect or any possible implementation of the first aspect.

[0024] In a third aspect, the present application provides a computer-readable storage medium storing a computer program. When the computer program runs on a processor, the processor executes the method described in the first aspect or any possible implementation of the first aspect.

[0025] In general, the above technical solutions conceived by this application have the following beneficial effects compared with the existing technologies:

[0026] (1) The adjustment method proposed in this application is based on modulation state decomposition, which divides the modulation state at the time of final measurement into multiple modulation states that are adjusted step by step. The channel distribution of its theoretical spectrum is used to determine whether the azimuth angle of the polarization element is adjusted in place. It effectively avoids the use of a mounting frame with a differential head and does not require any additional measuring instruments, thus achieving faster and more accurate component adjustment and adapting to a more compact and low-cost instrument structure design.

[0027] (2) This application uses spectral signals of different modulation states during the installation process to calibrate the wave plate. The calibration can be completed when the installation is completed, which is more convenient and faster, and does not require the use of additional standard components. On the one hand, it avoids calibration errors caused by manufacturing errors of standard components, and on the other hand, it further reduces the cost of instrument installation and calibration.

[0028] (3) The present invention uses a combination of multiple channels to calibrate the wave plate, effectively reducing the errors caused by light source fluctuations and random noise, and can effectively adapt to various installation and adjustment scenarios to achieve higher-precision instrument calibration. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a flow chart of the wide-spectrum snapshot ellipsometer assembly and calibration method provided in Example 1 of the present application.

[0030] Figure 2 This is a schematic diagram of the straight-through structure of the wide-spectrum snapshot ellipsometer provided in Example 2 of the present application during assembly, adjustment and calibration.

[0031] Figure 3 This is a flow chart of the wide-spectrum snapshot ellipsometer assembly and calibration method provided in Example 2 of the present application.

[0032] Figure 4 This is a simulation diagram of the theoretical channel distribution under various modulation states provided in Example 2 of the present application.

[0033] Figure 5 This is the actual channel distribution under different modulation states provided in Example 2 of the present application, as well as the channel combination intercepted during calibration.

[0034] Figure 6 It is a schematic diagram comparing the actual spectral signal and the signal generated by the calibrated delay amount in the intermediate modulation state and the final modulation state after the instrument is installed and calibrated, provided in Example 2 of the present application.

[0035] Figure 7 This is a structural diagram of an electronic device provided in an embodiment of the present application.

[0036] Throughout the drawings, the same reference numerals are used to denote the same elements or structures, wherein:

[0037] 1 is a broadband light source; 2 is a mounting housing; 3 is a collimating lens; 4 is a polarizer; 5 is a first multi-stage wave plate; 6 is a fixing pin; 7 is a second multi-stage wave plate; 8 is an analyzer; 9 is a converging lens; and 10 is a spectrometer. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solutions and advantages of this application more clear, the following further describes this application in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0039] In the specification and claims herein, the terms "first" and "second" are used to distinguish different objects rather than to describe a specific order of objects. For example, a first multi-stage wave plate and a second multi-stage wave plate are used to distinguish different multi-stage wave plates rather than to describe a specific order of multi-stage wave plates.

[0040] In the embodiments of this application, words such as "exemplary" or "for example" are used to indicate examples, illustrations, or descriptions. Any embodiment or design described as "exemplary" or "for example" in the embodiments of this application should not be interpreted as being preferred or advantageous over other embodiments or designs. Rather, the use of words such as "exemplary" or "for example" is intended to present the relevant concepts in a concrete manner.

[0041] In the description of the embodiments of the present application, unless otherwise specified, "multiple" means two or more than two, for example, multiple modulation states refer to two or more modulation states, etc.; multiple wave plates refer to two or more wave plates, etc.

[0042] The technical solution of this application is now introduced through multiple embodiments.

[0043] Example 1:

[0044] like Figure 1 As shown, Example 1 of the present application includes the following steps:

[0045] The adjustment process is divided into N+1 modulation states; N is the number of wave plates in the ellipsometer, the initial modulation state is the relative zero degree state between the polarization elements, the final modulation state is the state during measurement, and the intermediate N-1 modulation states are the N-1 intermediate states from the initial modulation state to the final modulation state.

[0046] Obtain the channel distribution of the theoretical spectral signal under each modulation state;

[0047] The ellipsometer is adjusted step by step according to the state of each modulation state so that the channel distribution of the actual spectral signal in each modulation state is closest to the channel distribution of the corresponding theoretical spectral signal;

[0048] Different channels are intercepted from the channel distribution of the actual spectral signal, and the phase delay of each wave plate is obtained by combining them after inverse Fourier transformation, thereby completing the calibration of the ellipsometer.

[0049] Example 2:

[0050] like Figure 2The ellipsometer used in Example 2 of the present application is shown, which includes a broadband light source 1, a mounting housing 2, a collimating lens 3, a polarizer 4, a first multi-stage wave plate 5, a fixing pin 6, a second multi-stage wave plate 7, an analyzer 8, a converging lens 9, and a spectrometer 10. In this embodiment, the ellipsometer does not require a high-precision mounting frame for assembly and adjustment.

[0051] like Figure 3 As shown, Example 2 of the present application includes the following steps:

[0052] S1. Divide the ellipsometer setup process into multiple modulation states and design a modulation state decomposition strategy. Decompose the modulation state into one initial modulation state and N intermediate modulation states, where N is the number of wave plates in the ellipsometer. The initial modulation state is set to zero relative angles between all polarization elements in the ellipsometer, and the last intermediate modulation state is the ellipsometer's measurement state. The theoretical channel distribution of the ellipsometer for each modulation state is then derived.

[0053] In this embodiment 2, the final modulation state of the ellipsometer, that is, the measurement state of the ellipsometer, is specifically: the transmission axis azimuth angle of the polarizer 4 is 0°, the fast axis azimuth angle of the first multi-order wave plate 5 is 45°, the fast axis azimuth angle of the second multi-order wave plate 7 is 0°, and the transmission axis azimuth angle of the analyzer 8 is 45°, which can be simply represented as 0-45-0-45, where the thickness ratio of the first multi-order wave plate to the second multi-order wave plate is 3:1.

[0054] During the assembly and calibration process, the modulation state decomposition is performed. The ellipsometer has two multi-stage wave plates, and N=2:

[0055] (1) Initial modulation state: The initial modulation state is set so that the relative angles between all polarization elements in the ellipsometer are zero, which is abbreviated as: 0-0-0-0;

[0056] At this time, the spectral signal in the wavenumber domain and channel distribution The expressions are:

[0057]

[0058]

[0059] in, is the spectral response of the light source, is the channel distribution of the light source, and the channel distribution is obtained at this time The characteristic is that there is only a zero-frequency (low-frequency) channel and no high-frequency channel generated by multi-level wave plates.

[0060] (2) First intermediate modulation state: 0-45-0-0;

[0061] The collected spectral signal is first divided by the spectral signal of the initial modulation state to remove the influence of the light source morphology on the channel distribution. After that, the spectral signal and channel distribution expressions in the wavenumber domain are:

[0062]

[0063]

[0064] Since the first multi-level wave plate is involved in the modulation at this time, its thickness is three times that of the second multi-level wave plate, so the corresponding modulation channel center frequency is also three times that of the second multi-level wave plate. The modulation channel center frequency of the second multi-level wave plate is recorded as frequency 1 (base frequency). ), the first multi-level wave plate is 3-frequency ( ). Based on the above analysis, the channel distribution is obtained at this time The characteristic is that it only has zero frequency and ±3 frequencies, and its spectral signal itself is a quasi-trigonometric function with a value range of [0, 1]; is the phase angle of the first modulation channel, is the imaginary unit, is the base of natural logarithms, represents the impulse function.

[0065] (3) Second intermediate modulation state (ellipsometer measurement state): 0-45-0-45;

[0066] According to the processing method described for the first intermediate modulation state, the spectral signal and channel distribution expressions of the second intermediate modulation state are respectively:

[0067]

[0068]

[0069] At this time, both multi-level wave plates participate in the modulation, and the spectral signal From the expression of , we can see that the sum and difference of the two appear. Then, combined with the analysis of the first intermediate state, we can get the channel distribution The characteristic is that there are only zero frequency, ±2 frequency and ±4 frequency. Among them, is the phase angle of the second modulation channel.

[0070] At this point, the decomposition strategy of the modulation state is designed and the simulation of the modulation process is carried out. The evolution of the theoretical channel distribution is shown as follows: Figure 4 shown.

[0071] S2. Install all components according to the requirements of the initial modulation state: Install the polarizer to any angle, determine the system relative to 0 degrees, use the spectrometer to collect the signal, and display its waveform and channel distribution in real time. Install the remaining components one by one, adjust the angle so that the wavelength distribution of the spectral signal meets the channel distribution of the theoretical spectral signal of the initial modulation state, and then adjust it to relative 0 degrees to record the actual spectral signal.

[0072] In this embodiment 2, the channel distribution of the initial modulation state is The characteristic is that there is only a zero-frequency (low-frequency) channel and no high-frequency channel generated by the multi-stage wave plate. After installing the polarizer, record the zero-frequency intensity of its channel distribution. When installing the remaining components one by one, on the one hand, ensure that the channel distribution has only zero frequency. On the other hand, due to the influence of the transmittance of the remaining components, the zero-frequency intensity will decrease. Adjust the component angle so that the zero-frequency intensity is closest to the intensity when there is only a polarizer. In this way, it can ensure that the components are installed to a relative 0 degree with high precision and record the actual spectral signal. .

[0073] S3. Rotate the element angle according to the requirements of the intermediate modulation state: When rotating the element angle, observe the channel distribution of the spectral signal until it is closest to the channel distribution of the theoretical spectral signal of the corresponding intermediate modulation state derived in step S1, and record the actual spectral signal of each intermediate modulation state, and finally adjust to the state during measurement.

[0074] In this embodiment 2, two intermediate modulation states are designed. The angle of the first multi-stage wave plate is rotated to adjust the first intermediate modulation state. As the first multi-stage wave plate rotates, the channel distribution will gradually show ±3 frequencies. The experimental process is as follows: Figure 5 As shown in parts (a) and (b), when the angle is adjusted to the highest intensity of ±3 frequencies, it is the precise first intermediate modulation state, and the actual spectral signal at this time is recorded. ;

[0075] Then, the angle of the analyzer is rotated to adjust the second intermediate modulation state. As the analyzer rotates, the intensity of the ±3 frequency in the channel distribution will gradually weaken, and the ±2 frequency and ±4 frequency will gradually appear and strengthen. The experimental process is shown in parts (c) and (d) of Figure 5. When the angle is adjusted until the ±3 frequency completely disappears and the intensity of the ±2 frequency and ±4 frequency is the highest, it is the accurate second intermediate modulation state (also the measurement state of the ellipsometer), and the actual spectral signal at this time is recorded. , thus completing the installation and adjustment of the ellipsometer.

[0076] S4. Perform instrument calibration: Use the channel distribution of different intermediate modulation states to intercept the channels corresponding to the different wave plates to be calibrated, combine them after inverse Fourier transform, and then complete the calibration of all wave plates.

[0077] In this embodiment 2, Figure 5As shown in part (b), the +3 frequency of the first intermediate modulation state channel distribution is intercepted, and after being filled with 0 and inverse Fourier transform, we can get , extract its phase information to complete the calibration of the first multi-level wave plate; then Figure 5 As shown in part (d), the +2 frequency of the second intermediate modulation state channel distribution is intercepted, and after being filled with 0 and inverse Fourier transform, we can get , and then intercept its +4 frequency, and similarly we can get , then use the +3 frequency channel of the first intermediate state to combine with the +2 frequency and +4 frequency respectively, and perform the following processing:

[0078]

[0079] Can get By extracting its phase information, the calibration of the second multi-stage wave plate can be completed. In addition, due to the averaging of multiple channel combinations, the errors caused by light source fluctuations and random noise can be effectively reduced. It can effectively adapt to various installation and adjustment scenarios and achieve higher-precision instrument calibration.

[0080] At this point, the installation and calibration of the wide-spectrum snapshot ellipsometer have been completed, and the instrument calibration has been completed simultaneously. No high-precision mounting bracket, additional measuring instruments, or standard components are used in the process. In this embodiment, the calibrated multi-level wave plate information is used in combination with the theoretical instrument model to generate the spectral signals of the first intermediate modulation state and the final modulation state, and then compared with the actual spectral signals. The experimental results are shown in Figure 2. Figure 6 As shown, the root mean square error is maintained at the order of 0.01, which is in good agreement. This shows that the installation and adjustment of the instrument are in line with the design value and the calibration of the instrument is accurate, which fully proves the effectiveness and stability of the method of this application.

[0081] Based on the method in the above embodiment, the embodiment of the present application provides an electronic device, such as Figure 7 As shown, the system includes a processor, a communication interface, a memory, and a communication bus. The processor, the communication interface, and the memory communicate with each other via the communication bus. The processor can call logic instructions in the memory to execute the method in the above embodiment.

[0082] In addition, the logical instructions in the above-mentioned memory can be implemented in the form of a software functional unit and can be stored in a computer-readable storage medium when sold or used as an independent product. Based on this understanding, the technical solution of the present application, or the part that contributes to the existing technology, or the part of the technical solution, can be embodied in the form of a software product. The computer software product is stored in a storage medium and includes a number of instructions for enabling a computer device (which can be a personal computer, server, or network device, etc.) to execute all or part of the steps of the method described in each embodiment of the present application.

[0083] Based on the method in the above embodiment, an embodiment of the present application provides a computer-readable storage medium, which stores a computer program. When the computer program runs on a processor, the processor executes the method in the above embodiment.

[0084] Based on the method in the above embodiment, an embodiment of the present application provides a computer program product. When the computer program product runs on a processor, the processor executes the method in the above embodiment.

[0085] It is understood that the processor in the embodiments of the present application may be a central processing unit (CPU), other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field programmable gate arrays (FPGA), other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. The general-purpose processor may be a microprocessor or any conventional processor.

[0086] The method steps in the embodiments of the present application can be implemented by hardware or by a processor executing software instructions. The software instructions can be composed of corresponding software modules, which can be stored in random access memory (RAM), flash memory, read-only memory (ROM), programmable read-only memory (PROM), erasable programmable read-only memory (EPROM), electrically erasable programmable read-only memory (EEPROM), registers, hard disks, mobile hard disks, CD-ROMs, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor so that the processor can read information from the storage medium and write information to the storage medium. Of course, the storage medium can also be an integral part of the processor. The processor and storage medium can be located in an ASIC.

[0087] The above embodiments can be implemented in whole or in part using software, hardware, firmware, or any combination thereof. When implemented using software, they can be implemented in whole or in part in the form of a computer program product. The computer program product comprises one or more computer instructions. When loaded and executed on a computer, the computer program instructions fully or partially produce the processes or functions described in the embodiments of this application. The computer can be a general-purpose computer, a special-purpose computer, a computer network, or other programmable device. The computer instructions can be stored in a computer-readable storage medium or transmitted via the computer-readable storage medium. The computer instructions can be transmitted from one website, computer, server, or data center to another website, computer, server, or data center via wired (e.g., coaxial cable, optical fiber, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium accessible by a computer or a data storage device such as a server or data center that integrates one or more available media. The available medium can be magnetic media (e.g., floppy disk, hard disk, tape), optical media (e.g., DVD), or semiconductor media (e.g., solid-state drive (SSD)).

[0088] It will be understood that the various numerical numbers involved in the embodiments of the present application are merely distinctions for the convenience of description and are not intended to limit the scope of the embodiments of the present application.

[0089] It is easy for those skilled in the art to understand that the above is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the scope of protection of the present application.

Claims

1. A method for calibrating a wide-spectrum snapshot ellipsometer, characterized in that: include: The adjustment process is divided into N+1 modulation states; N is the number of wave plates in the ellipsometer, the initial modulation state is the relative zero degree state between the polarization elements, the final modulation state is the state during measurement, and the intermediate N-1 modulation states are the N-1 intermediate states from the initial modulation state to the final modulation state. Obtain the channel distribution of the theoretical spectral signal under each modulation state; The ellipsometer is adjusted step by step according to the state of each modulation state so that the channel distribution of the actual spectral signal in each modulation state is closest to the channel distribution of the corresponding theoretical spectral signal; Different channels are intercepted from the channel distribution of the actual spectral signal, and the phase delay of each wave plate is obtained by combining them after inverse Fourier transformation to complete the calibration of the ellipsometer; The spectral signal Specifically: in, is the spectral response of the light source, and the modulation effect of the N wave plates in the ellipsometer is coupled to k Different modulation channels, For the k The phase angle of each modulation channel, is the base of natural logarithms, is an imaginary unit; The channel distribution Specifically: in, is the channel distribution of the light source. The modulation effect of N wave plates in the ellipsometer will be coupled as k Different modulation channels, It is k The center frequency of the modulation channel, is the impulse function.

2. The calibration method according to claim 1, characterized in that: The modulation state is specifically the angle combination of all polarization elements in the ellipsometer; in different modulation states, the ellipsometer modulates in different states to generate polarized light, and demodulates in different states at the same time.

3. The calibration method according to claim 1, characterized in that: The spectral signal is a signal obtained by uniform sampling of the spectrometer in the wavenumber domain; the channel distribution is a series of Fourier coefficients in the optical path difference domain obtained after Fourier transforming the spectral signal.

4. The calibration method according to claim 1, characterized in that: The ellipsometer is adjusted step by step according to the state of each modulation step so that the channel distribution of the actual spectral signal under each modulation step is closest to the channel distribution of the corresponding theoretical spectral signal, specifically: The angle of the polarization element in the rotating ellipsometer reaches a state corresponding to the modulation state; The angle of the polarization element in the ellipsometer is fine-tuned until the channel distribution of the actual spectral signal output by the ellipsometer is closest to the channel distribution of the theoretical spectral signal under the corresponding modulation state.

5. The calibration method according to claim 1, characterized in that: Different channels are intercepted from the channel distribution of the actual spectrum signal, and are combined after inverse Fourier transformation to obtain the phase delay of each wave plate; wherein each wave plate has multiple combinations to obtain the phase delay.

6. The calibration method according to claim 1, characterized in that: Different channels are intercepted from the channel distribution of the actual spectral signal, and the phase delay of each wave plate is obtained by combining them after inverse Fourier transformation; different combination methods are selected to obtain the phase delay of the same wave plate, and then the obtained phase delays are averaged to obtain the final phase delay of the wave plate.

7. An electronic device, characterized in that: include: at least one memory for storing a computer program; At least one processor is used to execute the program stored in the memory. When the program stored in the memory is executed, the processor is used to execute the method according to any one of claims 1 to 6.

8. A computer-readable storage medium storing a computer program, characterized in that: When the computer program is executed on a processor, the processor is caused to execute the method according to any one of claims 1 to 6.

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