A method for assembling and adjusting a dual photoelastic modulation type ellipsometer

Abstract

The application belongs to the field of precise optical measuring instrument adjustment, and specifically discloses an adjustment method of a dual photoelastic modulation type ellipsometer. In view of the problem that the azimuth error calibration method of the dual photoelastic modulation type ellipsometer has low sensitivity at a specific azimuth angle, depends on air calibration, and is difficult to calibrate in situ, the application proposes an improved calibration and adjustment method. The method first improves the calibration sensitivity by changing the azimuth angle configuration, and then reduces the coarse adjustment error by using a rotary displacement table according to the calibration result. Meanwhile, an isotropic film is introduced as a reference, and calibration is only based on the Mueller matrix characteristics of the isotropic film, without the need for prior information of the sample, effectively avoiding the influence of the reference sample error. In addition, the method belongs to in-situ calibration technology, and can be directly used for sample measurement after adjustment and assembly, avoiding the introduction of additional errors, and being suitable for different wavelengths and various types of ellipsometers, and having good adaptability and adjustment precision.

Description

Technical Field

[0001] This application belongs to the field of precision optical measuring instrument assembly and adjustment, and more specifically, relates to an assembly and adjustment method for a dual-photoelastic modulation type ellipsometer. Background Technology

[0002] The dual-photoelastic modulation ellipsometer is a crucial component in the dynamic monitoring of materials and integrated circuit structures. Primarily composed of a polarizer and a photoelastic modulator, it has wide applications in materials analysis and integrated circuit measurement. Currently, the measurement principle of the dual-photoelastic modulation ellipsometer is based on a fixed measurement configuration, obtaining specific Mueller matrix elements of the sample based on the azimuth angle configuration. The measurement accuracy of the dual-photoelastic modulation ellipsometer is limited by the azimuth angle installation accuracy of key optical components in the system (such as the photoelastic modulator, analyzer, and polarizer). Therefore, precise assembly and adjustment of the dual-photoelastic modulation ellipsometer are essential.

[0003] The assembly and adjustment of existing dual-photoelastic modulation ellipsometers generally involves mounting the photoelastic modulator, polarizer, and analyzer at a specific preset azimuth angle using a rotary displacement stage. Assembly and adjustment are achieved through reference standards for key components and a precision rotary displacement stage. Other researchers have gone a step further, using air measurements to precisely calibrate the system's azimuth error based on a model, and then using feedback adjustments based on the calibration results to achieve precise assembly and adjustment.

[0004] However, in practice, it was found that regardless of the assembly and adjustment method used, significant assembly and adjustment errors exist. Even using only a rotary stage for assembly and adjustment inevitably results in azimuth errors due to reference errors in key components and installation errors in the rotary stage. Based on this, azimuth error calibration using a system model revealed poor sensitivity for specific azimuth configurations, and since it was not an in-situ calibration, certain errors still remained. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the purpose of this application is to provide an assembly and adjustment method for a dual-optical-elastic modulation type ellipsometer, which aims to solve the problem that it is difficult to achieve precise in-situ assembly and adjustment of the dual-optical-elastic modulation type ellipsometer.

[0006] To achieve the above objectives, in a first aspect, this application provides a method for assembling and adjusting a dual-optical-elastic modulation type ellipsometer, comprising: Azimuth error coarse adjustment: After all the components of the target dual-photoelastic modulation ellipsometer are installed, the azimuth of the polarization element is coarsely adjusted to the azimuth configuration value of the target dual-photoelastic modulation ellipsometer through a step-by-step azimuth calibration method. Fine-tuning of azimuth error: Based on the coarsely tuned dual photoelastic modulated ellipsometer, the azimuth of the polarization element and photoelastic modulator is finely adjusted multiple times so that the fitted light intensity coefficients corresponding to the three azimuth errors are reduced to the ideal value, which is considered as the assembly and adjustment are completed. The three azimuth angles are: the azimuth angle error of the analyzer compared to the analyzer arm photoelastic modulator, the azimuth angle error of the polarizer arm photoelastic modulator compared to the polarizer, and the azimuth angle error of the analyzer arm photoelastic modulator compared to the polarizer. The light intensity coefficient corresponds one-to-one with the zero-value elements, symmetric elements, or antisymmetric elements in the Mueller matrix of the isotropic thin film, and is obtained in the following way: after each fine adjustment, the emitted light intensity signal corresponding to the isotropic thin film reference sample is measured using the adjusted dual photoelastic modulation ellipsometer. Based on the measured emitted light intensity signal and the probe light intensity model, the light intensity coefficient is fitted by nonlinear regression.

[0007] Preferably, the light intensity coefficient is obtained by fitting a nonlinear regression model based on the measured emitted light intensity signal and the detected light intensity model, as follows: Based on the azimuth configuration value of each polarization element of the target dual-photoelastic modulated ellipsometer, a dual-photoelastic system model including azimuth error is constructed based on the Stokes-Mueller matrix; Substituting the Stokes polarization states of the polarizing arm and the analyzer arm, along with the sample Mueller matrix, into the expression for the emitted light intensity signal in the dual photoelastic system model that includes azimuth angle error, we obtain the probe light intensity model. By treating each azimuth error as an infinitesimal quantity, the probe light intensity model is simplified, resulting in the simplified expression for the relationship between each light intensity coefficient and the azimuth error of each polarization element. Based on the above relational expression, and considering the characteristics of the Mueller matrix of isotropic thin films, especially the zero-value elements, symmetric elements, or antisymmetric elements in the Mueller matrix, the characteristic light intensity coefficient of azimuth error is selected. Light intensity data is obtained by measuring isotropic thin films, and the selected light intensity coefficient is obtained by combining the light intensity detection model with nonlinear regression fitting.

[0008] Preferably, the step of constructing a dual-photoelastic system model including azimuth error based on the azimuth configuration value of each polarization element of the target dual-photoelastic modulation ellipsometer includes:

[0009] in, This indicates the Stokes polarization state of the pivot arm. This represents the Stokes polarization state of the analyzer arm. These are the Mueller matrix and rotation matrix of the polarizer, photoelastic modulator, respectively. The Stokes vector representing the emitted light. These are the azimuth angles of the analyzer and the two photoelastic modulators relative to the polarizer. Configure values ​​for the corresponding azimuth angles. and These represent the phase delay of the two photoelastic modulators, with subscripts 1 and 2 indicating the polarizer and analyzer photoelastic modulators in the dual-photoelastic modulation system, respectively. These are trigonometric function values ​​of the azimuth angle of the photoelastic modulator relative to the polarizer and analyzer, respectively. It is a trigonometric function value of the phase delay of the photoelastic modulator. The azimuth angle error between the polarizer and the photoelastic modulator is considered. To detect the azimuth error of the polarizer compared to the polarizer, The azimuth error between the analyzer and the photoelastic modulator of the analyzer arm. This represents the transpose of a matrix.

[0010] Preferably, the function value expressions are as follows:

[0011] Among them, peak latency Static delay Modulation frequency and initial phase These are the main parameters and intermediate variables of the photoelastic modulator. .

[0012] Preferably, the Stokes polarization states of the polarizing arm and the analyzer arm in the dual-photoelastic system model, which includes azimuth error, and the sample Mueller matrix are substituted together into the expression for the emitted light intensity signal, specifically: Substituting the Stokes polarization states of the polarizing arm and the analyzer arm, along with the sample Mueller matrix, from the dual photoelastic system model, which includes azimuth error, into the expression for the emitted light intensity signal, we arrive at the expression for the output light intensity signal. ,get

[0013] in, For the sample Mueller matrix, This represents the gain coefficient for light intensity detection. All of these include sample information and device azimuth information, collectively referred to as light intensity coefficients.

[0014] Preferably, the sample Mueller matrix as follows:

[0015]

[0016] in, Let be a rotation matrix. This refers to the azimuth angle of the reference frame relative to the polarizer reference frame when measuring the thin film by oblique incidence. Corresponding to the isotropic thin film itself The Mueller matrix, These represent the ellipticity parameters of the isotropic thin film.

[0017] Preferably, each azimuth error is simplified as an infinitesimal quantity, as follows:

[0018]

[0019] in, The azimuth angle error between the polarizer and the photoelastic modulator is considered. To detect the azimuth error of the polarizer compared to the polarizer, The azimuth error of the analyzer compared to the photoelastic modulator of the analyzer arm.

[0020] Preferably, the specific expression for the light intensity coefficient is as follows:

[0021] in, The sixteen Mueller matrix elements representing the sample These are trigonometric function values ​​of the azimuth angle of the photoelastic modulator relative to the polarizer and analyzer, respectively. It is the trigonometric function value of the phase delay of the photoelastic modulator.

[0022] To achieve the above objectives, in a second aspect, this application provides a computer-readable storage medium including instructions that, when executed on an electronic device, cause the electronic device to perform the assembly method as described in the first aspect.

[0023] It is understandable that the beneficial effects of the second aspect mentioned above can be found in the relevant descriptions in the first aspect mentioned above, and will not be repeated here.

[0024] Overall, the technical solutions conceived in this application have the following beneficial effects compared with the prior art: (1) In view of the problem that the azimuth error calibration method of dual-optical-elastic modulation ellipsometer has poor sensitivity under a specific azimuth configuration, this application improves the sensitivity of azimuth calibration by first changing the azimuth configuration, and then reduces the coarse adjustment azimuth error by rotating the displacement stage based on the calibration results.

[0025] (2) This application extends the traditional calibration method by measuring only air. It proposes an assembly and adjustment method by measuring isotropic thin films. This method only requires the characteristics of the Mueller matrix of isotropic thin films and does not require detailed prior information of the reference sample, i.e., the isotropic thin film. This can effectively avoid the influence of the error of the Mueller matrix of the reference sample, thereby improving the accuracy and stability of the assembly and adjustment.

[0026] (3) To address the problem that traditional methods are difficult to implement in-situ calibration, this application proposes an in-situ calibration and adjustment technique. After the calibration is completed, it can be directly used to measure the ellipticity parameters of the sample without the need for additional calibration to introduce other errors. At the same time, this method is based on the feedback of the measurement results to adjust the azimuth error, which is also applicable to other types of ellipsometers and different wavelengths. It can effectively adapt to various calibration scenarios and achieve higher precision instrument calibration. Attached Figure Description

[0027] Figure 1 This is a flowchart of a method for assembling and adjusting a dual-photoelastic modulation ellipsometer provided in an embodiment of this application.

[0028] Figure 2 This is a flowchart of fitting the light intensity coefficient provided in the embodiments of this application.

[0029] Figure 3 This is a schematic diagram of the structure of the dual-photoelastic modulation ellipsometer provided in the embodiments of this application.

[0030] In all the accompanying drawings, the same reference numerals are used to denote the same elements or structures, wherein: 101-Light source, 102-Collimating lens, 103-Polarizer, 104-Polarizer arm photoelastic modulator, 105-Sample position, 106-Analyzer arm photoelastic modulator, 107-Analyzer, 108-Collection lens, 109-Detector. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0032] In this application, the term "and / or" describes the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A existing alone, A and B existing simultaneously, and B existing alone. In this application, the symbol " / " indicates that the related objects are in an "or" relationship, for example, A / B means A or B.

[0033] In this application, the terms "first" and "second," etc., are used to distinguish different objects, not to describe a specific order of objects. For example, "first response message" and "second response message," etc., are used to distinguish different response messages, not to describe a specific order of response messages.

[0034] In the embodiments of this application, the terms "exemplary" or "for example" are used to indicate that something is an example, illustration, or description. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design. Specifically, the use of the terms "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0035] In the description of the embodiments of this application, unless otherwise stated, "multiple" means two or more, for example, multiple processing units means two or more processing units, multiple elements means two or more elements, etc.

[0036] The embodiments of this application are described below with reference to the accompanying drawings.

[0037] like Figure 1 As shown, this application provides a method for assembling and adjusting a dual-optical-elastic modulation type ellipsometer, including: Azimuth error coarse adjustment: After all the components of the target dual-photoelastic modulation ellipsometer are installed, the azimuth of the polarization element is coarsely adjusted to the azimuth configuration value of the target dual-photoelastic modulation ellipsometer through a step-by-step azimuth calibration method. Fine-tuning of azimuth errors: Based on the coarsely tuned dual-photoelastic modulation ellipsometer, the azimuth angles of the polarization element and photoelastic modulator are finely adjusted multiple times until the fitted light intensity coefficients corresponding to the three azimuth errors are reduced to the ideal values, at which point the setup is considered complete. The three azimuth angles are: the azimuth error of the analyzer compared to the analyzer arm photoelastic modulator, the azimuth error of the polarizer arm photoelastic modulator compared to the polarizer, and the azimuth error of the analyzer arm photoelastic modulator compared to the polarizer. The light intensity coefficients correspond one-to-one with the zero-value elements, symmetric elements, or antisymmetric elements in the Mueller matrix of the isotropic thin film, and are obtained in the following way: After each fine-tuning, the adjusted dual-photoelastic modulation ellipsometer is used to measure the emitted light intensity signal corresponding to the isotropic thin film reference sample. Based on the measured emitted light intensity signal and the probe light intensity model, the light intensity coefficients are fitted by nonlinear regression.

[0038] Preferably, such as Figure 2 As shown, the light intensity coefficients are obtained by fitting nonlinear regression based on the measured emitted light intensity signal and the probe light intensity model, as detailed below: (1) Based on the azimuth configuration value of each polarization element of the target dual-optical-elastic modulated ellipsometer, construct a dual-optical-elastic system model containing azimuth error based on the Stokes-Mueller matrix; (2) Substitute the Stokes polarization states of the polarizing arm and the analyzing arm and the sample Mueller matrix in the dual photoelastic system model containing azimuth error into the expression of the emitted light intensity signal to obtain the probe light intensity model. (3) Treat each azimuth error as an infinitesimal quantity and simplify the probe light intensity model to obtain the simplified expression of the relationship between each light intensity coefficient and the azimuth error of each polarization element; (4) Based on the above relational expression, and considering the characteristics of the Mueller matrix of isotropic thin films, especially the zero-value elements, symmetric elements or antisymmetric elements in the Mueller matrix, select the characteristic light intensity coefficient of azimuth angle error; (5) Obtain light intensity data by measuring isotropic thin films, combine with the light intensity detection model, and fit the value of the selected light intensity coefficient by nonlinear regression.

[0039] Preferably, the azimuth angles of the polarization elements of the dual-photoelastic modulation ellipsometer are all referenced to the azimuth angle of the polarizer as zero degrees. The azimuth angle of the photoelastic modulator in the polarizing arm is referenced to the polarizer, and the azimuth angle of the photoelastic modulator in the analyzing arm is referenced to the analyzer.

[0040] The system model formula for the polarizer arm PSG and the analyzer arm PSA of the dual photoelastic system is shown in the following equation:

[0041]

[0042] in, This indicates the Stokes polarization state of the pivot arm. This represents the Stokes polarization state of the analyzer arm. These are the Mueller matrix and rotation matrix of the polarizer, photoelastic modulator, respectively. Indicates the Stokes polarization state. These are the azimuth angles of the analyzer and the two photoelastic modulators relative to the polarizer. and These are the phase delays of the two photoelastic modulators, respectively. These are the trigonometric function values ​​of the double angle of the azimuth of the optical device, where C represents the cosine function value and S represents the sine function value, and the subscripts correspond to the respective angles. intermediate variables intermediate variables , It is a trigonometric function value of the phase delay of the photoelastic modulator, and the peak delay. Static delay Modulation frequency and initial phase These are the main parameters of the photoelastic modulator. Subscripts 1 and 2 correspond to the first and second photoelastic modulators in a dual-photoelastic modulation system, respectively, and determine the specific performance of the PEM. Its specific expression is shown in the following formula:

[0043]

[0044] Will and Substitute into the emitted light intensity collected by the detector We can obtain:

[0045] in, It is the sample Mueller matrix. This represents the gain coefficient for light intensity detection. It contains sample information and device azimuth information, and is called the light intensity coefficient.

[0046] The specific expression for the light intensity coefficient is shown in the following formula:

[0047] in, These sixteen elements represent the sixteen Mueller matrix elements of the sample.

[0048] Preferably, the azimuth error includes three components: the azimuth error of the polarizing arm photoelastic modulator compared to the polarizer. The azimuth error of the polarizer compared to the polarizer. The azimuth error of the analyzer compared to the photoelastic modulator of the analyzer arm. , respectively denoted as (i=1,2,3), the calculation model is simplified as follows, and Powers of 2 and above in (i=1,2,3) are considered 0: .

[0049] Preferably, the Mueller matrix of the isotropic thin film is considered as shown in the following equation:

[0050] in, It is the azimuth angle of the reference frame relative to the polarizer reference frame when measuring the thin film by oblique incidence. Corresponding to the isotropic thin film itself The Mueller matrix is ​​shown in the following equation:

[0051] Preferably, the azimuth configuration of the dual-optical-elastic modulation ellipsometer includes the following possibilities: namely At that time, the azimuth angles of the two photoelastic modulators are 0°, ±45°, or ±90°, etc., that is... , or Or ±90° Alternatively, at ±90°, in this configuration, the light intensity coefficient corresponds one-to-one with the Mueller matrix elements of the sample.

[0052] Preferably, in the step-by-step calibration method, the azimuth angle of the analyzer relative to the polarizer is adjusted to 90° or 0° by extinction or maximum light intensity. The air is measured by turning on only one photoelastic modulator, and the azimuth angle of the photoelastic modulator is obtained based on the fitting of a single photoelastic model. Considering that the single photoelastic model has poor sensitivity to azimuth angle calibration under the above-mentioned configuration, its adjustment value should be deviated from the target azimuth angle by 20°-30°. Calibration based on the azimuth angle of the single photoelastic model is performed at this position. With this as a reference, the azimuth angle of the photoelastic modulator is coarsely adjusted to the above-mentioned configuration.

[0053] Preferably, when measuring the isotropic thin film, the designed azimuth error characteristic light intensity coefficient is based on the zero value of the Mueller matrix elements of the isotropic thin film, i.e. and And the symmetric or antisymmetric characteristics of the elements of the Mueller matrix, such as , Therefore, the characteristic light intensity coefficient of the azimuth error is generally... The corresponding light intensity coefficient.

[0054] Preferably, the light intensity coefficient is obtained through nonlinear regression fitting, and the light intensity detection model, as described above, obtains the correspondence between the light intensity coefficient and the Mueller matrix through a theoretical system model based on a specific target configuration.

[0055] Example like Figure 3As shown, this embodiment provides a dual-photoelastic modulation ellipsometer, which, along the optical path, consists of a light source 101, a collimating lens 102, a polarizer 103, a polarizing arm photoelastic modulator 104, a sample position 105, an analyzer arm photoelastic modulator 106, an analyzer 107, a collecting lens 108, and a detector 109. The light source 101 and collimating lens 102 form the light source module, providing a parallel illumination beam to the system. The polarizer 103 and polarizing arm modulation unit 104 form the polarizing arm, used to modulate the polarization state of the beam incident on the sample. The analyzer arm modulation unit 106 and analyzer 107 form the analyzer arm, used to analyze the polarization state of the light emitted after passing through the sample. The polarizing arm and analyzer arm are located on either side of the sample position 105. The collecting lens 108 and detector 109 collect the light intensity signal.

[0056] The dual-optical-elastic modulation ellipsometer can only measure nine parameters, thus only a portion of the Mueller matrix can be measured. Generally, different azimuth configurations need to be designed to measure different Mueller matrix elements. This embodiment uses... This application is illustrated using one azimuth configuration as an example; the other azimuth configurations described above are also applicable to this application.

[0057] S1: Considering the azimuth error, that is, the azimuth error of the polarizer 104 compared to the polarizer 103. The azimuth error of the polarizer 106 compared to the polarizer 103 The azimuth error of the analyzer 107 compared to the photoelastic modulator 106 of the analyzer arm. , respectively denoted as (i=1,2,3), then the azimuth angles of the analyzer 107, the polarizer arm photoelastic modulator, and the analyzer arm photoelastic modulator are: ;correspond The system model of the polarization arm PSG and the polarization analyzer PSA of the dual photoelastic system is shown in the following equation:

[0058] in, and These are the phase delays of the two photoelastic modulators, respectively. These are the Mueller matrix and rotation matrix of the polarizer, the delay unit (photoelastic modulator), and the rotation matrix, respectively. This is the sample Mueller matrix. and Substitute into the emitted light intensity collected by the detector It can be obtained.

[0059] in, This includes sample information and device azimuth information, and is called the light intensity coefficient. The calculation model is simplified as follows: Powers of 2 and above are considered 0:

[0060] The simplified expression for the light intensity coefficient is shown in the following formula, where, These sixteen elements represent the sixteen Mueller matrix elements of the sample.

[0061]

[0062] S2: Based on the simplified relationship between the light intensity system and the Mueller matrix after considering the azimuth error, and taking into account the characteristics of the isotropic thin film Mueller matrix, its characteristics are as follows: ; To address the three azimuth errors mentioned above, the following characteristic light intensity coefficients for azimuth errors are designed: These coefficients address the azimuth error between the analyzer and the photoelastic modulator of the analyzer arm. The corresponding light intensity coefficient Regarding the azimuth error between the polarizer and the photoelastic modulator of the polarizer arm. The corresponding light intensity coefficient Regarding the azimuth error between the polarizer and the analyzer's photoelastic modulator. The corresponding light intensity coefficient (It should be noted that,) include ,add In order to eliminate The corresponding When performing precise adjustment of azimuth error, the azimuth angle of the polarization element is finely adjusted to set the intensity coefficients of the three azimuth error characteristics to zero, which is considered as the completion of the adjustment.

[0063] S3: Install all polarization elements. Using polarizer 103 as the reference zero degree, perform step-by-step calibration and coarse adjustment of the azimuth angles of analyzer 107, polarizer arm photoelastic modulator 104, and analyzer arm photoelastic modulator 106 sequentially using a step-by-step calibration and light intensity model fitting method. First, close the two photoelastics and adjust the azimuth angle of analyzer 107 to 0° by maximizing the detected light intensity. Then, according to the reference scales of the polarizer and photoelastic modulator, adjust the azimuth angles of the photoelastic modulators (polarizer arm photoelastic modulator 104 and analyzer arm photoelastic modulator 106) to 0°. The azimuth angle of the polarization arm photoelastic modulator 106 is coarsely adjusted to 20°-30°. Then, the polarization arm photoelastic modulator is turned on, and air is measured. The azimuth angle of the photoelastic modulator is calibrated based on the single photoelastic model fitting method. For the specific method, refer to patent CN118624537A. Based on the calibration result, the azimuth angle of the photoelastic modulator is coarsely adjusted to 45° by rotating the displacement stage. Then, the azimuth angle of the photoelastic modulator on the analyzer arm is coarsely adjusted to 45° in the same way. This completes the coarse adjustment of the dual photoelastic modulated ellipsometer.

[0064] S4: Measure the isotropic thin film reference sample using the coarsely tuned dual-photoelastic modulation ellipsometer described above, obtaining a series of time-varying measured modulation light intensity data. Extract the light intensity coefficients using a model-based light intensity fitting method, which are the azimuth error characteristic light intensity coefficients designed in step S2. Specific operation steps are as follows (both photoelastic modulators need to be turned on during the following processing): First, fine-tune the polarizing arm photoelastic modulator to adjust the extracted light intensity coefficient. When the value decreases to near zero, the azimuth error of the deflector photoelastic modulator is almost zero. Secondly, the polarizer photoelastic modulator is fine-tuned to adjust the extracted light intensity coefficient. When the value decreases to near zero, the azimuth error between the polarizer and the analyzer is almost zero. Finally, the photoelastic modulator and analyzer of the polarizer arm are finely adjusted simultaneously to extract the light intensity coefficient. When the value decreases to near zero, the azimuth error between the polarizer and the analyzer is almost zero, thus completing the precise adjustment of the polarization element azimuth of the dual-photoelastic modulation ellipsometer.

[0065] This completes the assembly and adjustment of the dual-optical-elastic modulation ellipsometer. In this embodiment, the fine-tuning range is... The order of the three fine-tuning steps mentioned above cannot be interchanged.

[0066] This method only requires knowledge of the characteristics of the Mueller matrix of isotropic thin films, without needing detailed prior information about the reference sample or isotropic thin film. It can effectively avoid the influence of the Mueller matrix error of the reference sample, thereby improving the accuracy and stability of the assembly and adjustment. At the same time, this method is an in-situ calibration and assembly technique. After the assembly and adjustment is completed, it can be directly used to measure the ellipticity parameters of the sample without introducing other errors through additional assembly and adjustment. Furthermore, this method is based on the feedback of the measurement results to adjust the azimuth error, and it is also applicable to other types of ellipsometers and different wavelengths. It can effectively adapt to various assembly and adjustment scenarios and achieve higher precision instrument assembly and calibration.

[0067] In summary, this application's method based on light intensity model fitting achieves precise calibration of the azimuth angle error of all polarization elements in a dual photoelastic modulation system by measuring isotropic thin films. This is an in-situ calibration method with high assembly and adjustment accuracy. Furthermore, it does not require precise information from a reference sample, but relies solely on the characteristics of the Mueller matrix of the isotropic thin film to achieve precise adjustment of the polarization element azimuth angle, thereby improving the measurement accuracy of specific Mueller matrix elements in the dual photoelastic system.

[0068] Based on the methods in the above embodiments, this application provides an electronic device that may include a processor, a communications interface, a memory, and a communication bus, wherein the processor, communications interface, and memory communicate with each other via the communication bus. The processor may invoke logical instructions stored in the memory to execute the methods in the above embodiments.

[0069] Furthermore, the logical instructions in the aforementioned memory can be implemented as software functional units and, when sold or used as independent products, can be stored in a 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.

[0070] Based on the methods in the above embodiments, this application provides a computer-readable storage medium storing a computer program that, when run on a processor, causes the processor to execute the methods in the above embodiments.

[0071] Based on the methods in the above embodiments, this application provides a computer program product that, when run on a processor, causes the processor to execute the methods in the above embodiments.

[0072] It is understood that the processor in the embodiments of this application can be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSPs), application-specific integrated circuits (ASICs), field-programmable gate arrays (FPGAs), or other programmable logic devices, transistor logic devices, hardware components, or any combination thereof. A general-purpose processor can be a microprocessor or any conventional processor.

[0073] The method steps in this application embodiment can be implemented in hardware or by a processor executing software instructions. The software instructions can consist 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, portable hard disks, CD-ROMs, or any other form of storage medium known in the art. An exemplary storage medium is coupled to the processor, enabling the processor to read information from and write information to the storage medium. Of course, the storage medium can also be a component of the processor. The processor and the storage medium can reside in an ASIC.

[0074] In the above embodiments, implementation can be achieved entirely or partially through software, hardware, firmware, or any combination thereof. When implemented using software, it can be implemented entirely or partially as a computer program product. The computer program product includes one or more computer instructions. When the computer program instructions are loaded and executed on a computer, all or part of the processes or functions described in the embodiments of this application are generated. 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 through 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, fiber optic, digital subscriber line (DSL)) or wireless (e.g., infrared, wireless, microwave, etc.) means. The computer-readable storage medium can be any available medium that a computer can access or a data storage device such as a server or data center that integrates one or more available media. The available medium can be a magnetic medium (e.g., floppy disk, hard disk, magnetic tape), an optical medium (e.g., DVD), or a semiconductor medium (e.g., solid-state disk (SSD)).

[0075] It is understood that the various numerical designations used in the embodiments of this application are merely for the convenience of description and are not intended to limit the scope of the embodiments of this application.

[0076] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for assembling and adjusting a dual-optical-elastic modulation type ellipsometer, characterized in that, include: Azimuth error coarse adjustment: After all the components of the target dual-photoelastic modulation ellipsometer are installed, the azimuth of the polarization element is coarsely adjusted to the azimuth configuration value of the target dual-photoelastic modulation ellipsometer through a step-by-step azimuth calibration method. Fine-tuning of azimuth error: Based on the coarsely tuned dual photoelastic modulated ellipsometer, the azimuth of the polarization element and photoelastic modulator is finely adjusted multiple times so that the fitted light intensity coefficients corresponding to the three azimuth errors are reduced to the ideal value, which is considered as the assembly and adjustment are completed. The three azimuth angles are: the azimuth angle error of the analyzer compared to the analyzer arm photoelastic modulator, the azimuth angle error of the polarizer arm photoelastic modulator compared to the polarizer, and the azimuth angle error of the analyzer arm photoelastic modulator compared to the polarizer. The light intensity coefficient corresponds one-to-one with the zero-value elements, symmetric elements, or antisymmetric elements in the Mueller matrix of the isotropic thin film, and is obtained in the following way: after each fine adjustment, the emitted light intensity signal corresponding to the isotropic thin film reference sample is measured using the adjusted dual photoelastic modulation ellipsometer. Based on the measured emitted light intensity signal and the probe light intensity model, the light intensity coefficient is fitted by nonlinear regression.

2. The assembly and adjustment method as described in claim 1, characterized in that, Based on the measured emitted light intensity signal and the probe light intensity model, the light intensity coefficient is fitted by nonlinear regression, as follows: Based on the azimuth configuration value of each polarization element of the target dual-photoelastic modulated ellipsometer, a dual-photoelastic system model including azimuth error is constructed based on the Stokes-Mueller matrix; Substituting the Stokes polarization states of the polarizing arm and the analyzer arm, along with the sample Mueller matrix, into the expression for the emitted light intensity signal in the dual photoelastic system model that includes azimuth angle error, we obtain the probe light intensity model. By treating each azimuth error as an infinitesimal quantity, the probe light intensity model is simplified, resulting in the simplified expression for the relationship between each light intensity coefficient and the azimuth error of each polarization element. Based on the above relational expression, and considering the characteristics of the Mueller matrix of isotropic thin films, especially the zero-value elements, symmetric elements, or antisymmetric elements in the Mueller matrix, the characteristic light intensity coefficient of azimuth error is selected. Light intensity data is obtained by measuring isotropic thin films, and the selected light intensity coefficient is obtained by combining the light intensity detection model with nonlinear regression fitting.

3. The assembly and adjustment method as described in claim 2, characterized in that, The construction of a dual-photoelastic system model, including azimuth error, based on the azimuth configuration values ​​of each polarization element of the target dual-photoelastic modulated ellipsometer and the Stokes-Mueller matrix includes: in, This indicates the Stokes polarization state of the pivot arm. This represents the Stokes polarization state of the analyzer arm. These are the Mueller matrix and rotation matrix of the polarizer, photoelastic modulator, respectively. The Stokes vector representing the emitted light. These are the azimuth angles of the analyzer and the two photoelastic modulators relative to the polarizer. Configure values ​​for the corresponding azimuth angles. and These represent the phase delay of the two photoelastic modulators, with subscripts 1 and 2 indicating the polarizer and analyzer photoelastic modulators in the dual-photoelastic modulation system, respectively. These are trigonometric function values ​​of the azimuth angle of the photoelastic modulator relative to the polarizer and analyzer, respectively. It is a trigonometric function value of the phase delay of the photoelastic modulator. The azimuth angle error between the polarizer and the photoelastic modulator is considered. To detect the azimuth error of the polarizer compared to the polarizer, The azimuth error between the analyzer and the photoelastic modulator of the analyzer arm. This represents the transpose of a matrix.

4. The assembly and adjustment method as described in claim 3, characterized in that, The function value expressions are as follows: Among them, peak latency Static delay Modulation frequency and initial phase These are the main parameters and intermediate variables of the photoelastic modulator. .

5. The assembly and adjustment method as described in claim 2, characterized in that, Substituting the Stokes polarization states of the polarizing arm and the analyzer arm, along with the sample Mueller matrix, into the expression for the emitted light intensity signal in the dual-photoelastic system model that includes azimuth error, is as follows: Substituting the Stokes polarization states of the polarizing arm and the analyzer arm, along with the sample Mueller matrix, from the dual photoelastic system model, which includes azimuth error, into the expression for the emitted light intensity signal, we arrive at the expression for the output light intensity signal. ,get in, For the sample Mueller matrix, This represents the gain coefficient for light intensity detection. All of these include sample information and device azimuth information, collectively referred to as light intensity coefficients.

6. The assembly and adjustment method as described in claim 5, characterized in that, Sample Mueller matrix as follows: in, Let be a rotation matrix. This refers to the azimuth angle of the reference frame relative to the polarizer reference frame when measuring the thin film by oblique incidence. Corresponding to the isotropic thin film itself The Mueller matrix, These represent the ellipticity parameters of the isotropic thin film.

7. The assembly and adjustment method as described in claim 5, characterized in that, Each azimuth error is simplified as an infinitesimal quantity, as follows: in, The azimuth angle error between the polarizer and the photoelastic modulator is considered. To detect the azimuth error of the polarizer compared to the polarizer, The azimuth error of the analyzer compared to the photoelastic modulator of the analyzer arm.

8. The assembly and adjustment method as described in claim 5, characterized in that, The specific expression for the light intensity coefficient is as follows: in, The sixteen Mueller matrix elements representing the sample These are trigonometric function values ​​of the azimuth angle of the photoelastic modulator relative to the polarizer and analyzer, respectively. It is the trigonometric function value of the phase delay of the photoelastic modulator.

9. A computer-readable storage medium, characterized in that, Includes instructions that, when executed on an electronic device, cause the electronic device to perform the assembly method as described in any one of claims 1 to 8.

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