Metal film size measurement method and system based on optical measurement

Abstract

The invention relates to the technical field of optical measurement, and discloses a metal film size measurement method and system based on optical measurement, and the method comprises the steps: irradiating a metal film through a multi-wavelength laser, and generating an interference signal; carrying out attention modulation on the wavelength of the incident light, and respectively adjusting the attention of different wavelengths by sliding a time window; obtaining interference fringes in each time window, and obtaining a measurement result of each time window according to the interference fringes; and performing clustering selection according to the measurement result of the time window, and performing re-measurement by using a selection result to obtain a final measurement result. And the measurement precision and stability of the metal film size can be effectively improved. The attention of different wavelengths is dynamically adjusted, and the wavelength sensitive to parameters is selected in combination with clustering selection and a re-measurement process, so that the reliability of a final measurement result is ensured, and the high requirements of modern precision manufacturing and quality control on film size measurement are met.

Description

Technical Field

[0001] The present invention relates to the technical field of optical measurement, and in particular to a metal film size measurement method and system based on optical measurement. Background Art

[0002] With the widespread application of metal films in electronics, optics, semiconductors and other fields, the demand for accurate measurement of their dimensions is increasing. Although traditional dimension measurement methods, such as contact probe method and scanning electron microscope (SEM), have high accuracy, they often have problems such as contact damage, slow measurement speed, and high equipment cost. Optical measurement technology, especially non-contact measurement methods based on interference effect, has gradually become an important means of thin film dimension measurement due to its advantages of high precision, fast speed and non-destructiveness.

[0003] At present, there are thin film thickness measurement methods based on interference technology, but due to the different sensitivity of interference fringes of different wavelengths to the film size, and the possible presence of signal noise and multiple interferences in practical applications, the measurement accuracy of a single wavelength is limited. Therefore, how to use multi-wavelength laser light sources, through reasonable interference fringe analysis and data processing technology, to improve the comprehensive measurement accuracy of the length, width and thickness of metal films has become an important direction of current technological development. Summary of the invention

[0004] In view of the above-mentioned problems, the present invention is proposed.

[0005] Therefore, the technical problems solved by the present invention are: the measurement accuracy of a single wavelength is limited, the interference fringes of different wavelengths have different sensitivities to the film size, and in practical applications, there may be problems such as signal noise and multiple interferences.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions: a metal film size measurement method based on optical measurement, comprising: The metal film is irradiated by a multi-wavelength laser to generate an interference signal; Modulate the wavelength of the incident light and adjust the attention of different wavelengths by sliding the time window; Obtaining interference fringes in each time window, and obtaining a measurement result of each time window based on the interference fringes; Cluster selection is performed according to the measurement results of the time window, and re-measurement is performed using the selection results to obtain the final measurement results.

[0007] As a preferred solution of the metal film size measurement method based on optical measurement described in the present invention, wherein: the multi-wavelength laser includes randomly selecting N laser sources with different wavelengths to form an incident light combination; The selected multi-wavelength laser source is irradiated onto the metal film. The laser beam interacts with the surface. A high-resolution CCD or CMOS camera is used to receive the reflected light and capture the interference images at different wavelengths to obtain the interference fringe pattern generated by each wavelength of laser.

[0008] As a preferred solution of the metal film size measurement method based on optical measurement described in the present invention, wherein: the modulation of the wavelength of the incident light includes weighting the analysis results of N different wavelengths; Randomly select a wavelength from N interference signals with different wavelengths and set it as m; After obtaining the interference fringe pattern generated by the laser of each wavelength, the interference fringe pattern corresponding to each wavelength is analyzed, and the analysis results of each wavelength are integrated; During integration, the parsing results corresponding to wavelength m are subjected to attention weighting processing; The analysis process includes obtaining the surface morphological characteristics of the film by performing surface fitting on the edge position and shape of the interference fringes; and obtaining thickness information by calculating using the spacing of the interference fringes, the thickness of the film, the refractive index, the angle of incidence, and the wavelength of the light wave.

[0009] As a preferred solution of the metal film size measurement method based on optical measurement described in the present invention, wherein: the adjustment of attention to different wavelengths by sliding the time window includes setting a fixed time window length, randomly selecting a wavelength in each time window, and performing attention weighting processing on the corresponding analysis result; The constraint when selecting the wavelength is that the selected wavelengths in N consecutive time windows are all different.

[0010] As a preferred solution of the metal film size measurement method based on optical measurement described in the present invention, wherein: the measurement result of each time window includes weighting the analysis results corresponding to N wavelengths in each time window; assuming, represents the weight coefficient. If n corresponds to the analytical result corresponding to the unweighted wavelength, then ; If n corresponds to the analytical result corresponding to the weighted wavelength, then ; M represents a weighting coefficient, and M>2; i∈{C, K, G}, C represents the length of the metal film, K represents the width of the metal film, and G represents the thickness of the metal film; For each parameter i of the metal film, M analysis results corresponding to the weighted wavelength are copied according to the weight coefficient, and the analysis results corresponding to other N-1 wavelengths form a parameter set as the measurement result.

[0011] As a preferred solution of the metal film size measurement method based on optical measurement described in the present invention, wherein: performing cluster selection according to the measurement result of the time window includes obtaining N consecutive time windows forward from the current time series, and performing cluster selection for each parameter i of the metal film in any time window; The cluster selection includes clustering the measurement results. If there is only one cluster center, the wavelength of the current window attention weighting is determined. For the measurement result of the metal film parameter i, The criterion is satisfied; otherwise, it is judged that the criterion is not satisfied; The re-measurement includes removing k wavelengths that do not meet the criteria from N different wavelengths, and if the number of remaining wavelengths is less than N / 2, randomly selecting k other wavelengths, and performing interference fringe analysis and cluster selection on the re-selected wavelengths in a sliding time window until the remaining wavelengths are not less than N / 2 after the wavelengths that do not meet the criteria are removed; obtaining the analysis results of the wavelengths that meet the criteria corresponding to the parameter i, and outputting them; The k other wavelengths do not include the removed wavelengths; the reselected wavelengths include the remaining wavelengths that meet the criterion and the newly added k other wavelengths.

[0012] As a preferred solution of the metal film size measurement method based on optical measurement described in the present invention, wherein: the final measurement result includes cluster selection and re-measurement of the two parameters C and K at the same time; after the output is completed, cluster selection and re-measurement of the parameter G; When all three parameters have completed cluster selection and remeasurement and output, the test process ends; The average of the analytical results of the parameter i corresponding to the wavelengths satisfying the criterion is calculated to obtain the final measurement result; The following constraints are included in the process of randomly selecting multiple wavelengths: N>3; The maximum difference of multiple randomly selected wavelengths is not less than E; Wherein, E represents the threshold value of the maximum wavelength difference.

[0013] A metal film size measurement system based on optical measurement using any method described in the present invention, characterized in that: The acquisition unit irradiates the metal film with a multi-wavelength laser to generate an interference signal; The attention control unit modulates the wavelength of the incident light and adjusts the attention of different wavelengths by sliding the time window; A measuring unit, which obtains interference fringes in each time window and obtains a measurement result of each time window according to the interference fringes; The output unit performs cluster selection according to the measurement results of the time window, and remeasures using the selection results until the criterion is met to obtain the final measurement result.

[0014] A computer device comprises: a memory and a processor; the memory stores a computer program, wherein: the processor implements the steps of any one of the methods of the present invention when executing the computer program.

[0015] A computer-readable storage medium stores a computer program, wherein: when the computer program is executed by a processor, the steps of any one of the methods of the present invention are implemented.

[0016] Beneficial effects of the present invention: The optical measurement-based metal film dimension measurement method provided by the present invention can effectively improve the measurement accuracy and stability of the metal film dimension (length, width, thickness) by using multi-wavelength laser interferometry measurement technology, combined with sliding time window and weighted analysis method. By dynamically adjusting the attention of different wavelengths, combining cluster selection and re-measurement process to select wavelengths sensitive to parameters, the reliability of the final measurement result is guaranteed, with high adaptability and accuracy, meeting the high requirements of modern precision manufacturing and quality control for film dimension measurement. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative work.

[0018] Figure 1 An overall flow chart of a metal film size measurement method based on optical measurement provided in the first embodiment of the present invention. DETAILED DESCRIPTION

[0019] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are described in detail below in conjunction with the drawings of the specification. Obviously, the described embodiments are part of the embodiments of the present invention, but not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary persons in the art without creative work should fall within the scope of protection of the present invention.

[0020] Example 1, reference Figure 1 , as an embodiment of the present invention, provides a metal film size measurement method based on optical measurement, comprising: S1: Multi-wavelength lasers are used to illuminate the metal film to generate interference signals.

[0021] The multi-wavelength laser includes randomly selecting N laser sources with different wavelengths to form an incident light combination. The selected multi-wavelength laser source is irradiated onto the metal film, the laser beam interacts with the surface, and a high-resolution CCD or CMOS camera is used to receive the reflected light, capture interference images at different wavelengths, and obtain the interference fringe pattern generated by each wavelength of laser.

[0022] It is important to say that when a laser beam is irradiated onto the surface of a metal film, the reflected light will interfere with the light reflected from the film surface. At the film surface, the phase and path difference of the light wave will change due to the thickness and surface shape of the film, resulting in constructive and destructive interference between the light waves. Light of different wavelengths will have different spacing of interference fringes due to their different wavelengths. Longer wavelengths produce interference fringes with larger spacing, while shorter wavelengths produce denser interference fringes. This allows a variety of interference patterns to be obtained through a multi-wavelength laser source, and the interference fringes produced by each wavelength are superimposed in space to form a composite interference pattern. After being scattered or reflected by the film surface, the reflected light enters a high-resolution CCD or CMOS camera. These cameras can capture interference images at different wavelengths and record the intensity distribution and phase change of the reflected light. The interference pattern corresponding to each wavelength appears as periodic fringes or alternating patterns of light and dark in the image. The camera transmits the captured image to a computer for further processing. Using image processing algorithms (such as edge detection, Fourier analysis, etc.), information such as the position, spacing, and shape of the interference fringes can be extracted from the captured interference pattern.

[0023] The interference pattern of each wavelength will show a specific fringe distribution, which can be straight, curved or circular, etc., depending on the laser incident angle, the surface morphology of the film and the refractive index. The spacing of the interference fringes is closely related to the thickness of the film, the refractive index, the incident angle and the laser wavelength. By measuring the spacing of these fringes, the thickness and other geometric characteristics of the film can be inferred.

[0024] The composite interference pattern contains multiple different frequency components. Extracting a single wavelength pattern from the composite interference pattern mainly relies on image processing techniques such as Fourier transform, frequency domain filtering, and fringe period analysis. By analyzing the frequency components, period, and phase differences of the interference fringes, the interference fringes of each wavelength can be effectively separated from the composite pattern, thereby realizing the extraction of a single wavelength interference pattern. Among them, Fourier transform is an effective frequency domain analysis method that can convert the spatial information in the image into frequency domain information, helping to separate the interference fringes generated by different wavelengths.

[0025] S2: Modulate the wavelength of the incident light and adjust the attention of different wavelengths by sliding the time window.

[0026] The modulation of the wavelength of the incident light includes weighting the analysis results of N different wavelengths. Randomly select a wavelength from the interference signals of N different wavelengths and set it as m. After obtaining the interference fringe pattern generated by the laser of each wavelength, the interference fringe pattern corresponding to each wavelength is analyzed, and the analysis results of each wavelength are integrated. When integrating, the analysis results corresponding to the wavelength m are weighted. Among them, the analysis process includes obtaining the surface morphological characteristics of the film by performing surface fitting on the edge position and morphology of the interference fringes; and calculating using the spacing of the interference fringes, the thickness of the film, the refractive index, the angle of incidence, and the wavelength of the light wave to obtain the thickness information.

[0027] It is important to know that by combining interference signals from multiple wavelengths, the limitations of single-wavelength lasers can be overcome and measurement errors can be reduced. Interference fringes of different wavelengths have different sensitivities under different conditions, which can provide more measurement information.

[0028] It should be noted that in multi-wavelength laser interferometry, each wavelength responds differently to the reflection and interference signals of the film. Therefore, the interference fringes corresponding to different wavelengths may have different sensitivities to different size features of the film. By randomly selecting different wavelengths for analysis and weighting, the advantages of each wavelength can be fully utilized to avoid the measurement error of a single wavelength on certain sizes or surface features, thereby improving the overall accuracy of the measurement results.

[0029] Interference patterns at different wavelengths may be affected by different degrees of noise. By weighting the analytical results of different wavelengths, especially paying more attention to certain wavelengths, the contribution of those wavelength measurement results with more reliability is enhanced, thus making itself a clustering center.

[0030] The adjustment of attention to different wavelengths by sliding the time window includes setting a fixed time window length, randomly selecting a wavelength in each time window, and performing attention weighting processing on the corresponding analysis result. The constraint when selecting the wavelength is that the selected wavelengths in the consecutive N time windows are all different.

[0031] It should be noted that the interference signals at different wavelengths may have different sensitivities to parameters such as film thickness and surface morphology. By sliding the time window and selecting different wavelengths, the effect of the interference signals in each time window can be enhanced, and the reliability of the interference signals can be inferred based on their prominence.

[0032] S3: Obtain interference fringes in each time window, and obtain a measurement result of each time window according to the interference fringes.

[0033] The measurement result of each time window includes weighting the analysis results corresponding to N wavelengths in each time window; assuming that, represents the weight coefficient. If n corresponds to the analytical result corresponding to the unweighted wavelength, then ; If n corresponds to the analytical result corresponding to the weighted wavelength, then ; M represents the weighting coefficient, and M>2; i∈{C, K, G}, C represents the length of the metal film, K represents the width of the metal film, and G represents the thickness of the metal film.

[0034] For each parameter i of the metal film, M analysis results corresponding to the weighted wavelength are copied according to the weight coefficient, and the analysis results corresponding to other N-1 wavelengths form a parameter set as the measurement result.

[0035] It is important to mention that the multi-head attention strategy strengthens the features of different wavelengths in different time windows, and increases the influence in the clustering process by weighting and replicating the analysis results of the weighted wavelengths. In multi-wavelength optical measurements, different wavelengths have different sensitivities to different parameters of the film (such as length, width, and thickness). By weighting and replicating the analysis results of different wavelengths in each time window, the influence of different wavelengths is intentionally enhanced, so that the analysis results of the wavelengths with attention can become a clustering center by themselves. This is conducive to screening wavelengths that are sensitive to each parameter in the cluster selection process.

[0036] S4: performing cluster selection according to the measurement results of the time window, and re-measuring using the selection results to obtain a final measurement result.

[0037] Furthermore, cluster selection based on the measurement results of the time window includes obtaining N consecutive time windows from the current time series, and performing cluster selection for each parameter i of the metal film in any time window. The cluster selection includes clustering the measurement results, and if there is only one cluster center, determining the wavelength of the current window attention weighting, and the measurement results of the metal film parameter i The criterion is satisfied; otherwise, it is judged that the criterion is not satisfied (the purpose of this step is to screen the wavelengths that are sensitive to parameter i).

[0038] It is important to know that within each time window, the analysis results of different wavelengths are weighted, especially the attention weighting of a certain wavelength, which means that the data of this wavelength is considered to be more important in the current time window. Therefore, the weighted wavelength is more likely to become the "dominant" data in the cluster analysis, while other wavelengths may only participate in the clustering as supplementary data. If the analysis results of the weighted wavelength (the wavelength enhanced by the attention mechanism) are consistent with the results of other wavelengths (that is, a single cluster center is formed), it means that the data of these weighted wavelengths are consistent with the measurement results of most other wavelengths, and can be regarded as normal and reliable.

[0039] In multi-wavelength optical measurements, each wavelength has a different sensitivity to film parameters. Each time a measurement is made, the interference fringes produced by different wavelengths will reflect different degrees of surface morphological characteristics. Therefore, the analysis results of multiple wavelengths may show different fluctuations or errors. If the analysis results of a certain wavelength are inconsistent with the analysis results of other wavelengths, this may mean that the measurement results of that wavelength are inaccurate or unreliable. Cluster analysis is used to group the measurement results of these wavelengths and judge the reliability of these results by whether there is only one cluster center.

[0040] There is only one cluster center: If after cluster analysis, the analysis results of all wavelengths form a cluster center, then these analysis results are consistent with each other and conform to the actual measurement situation, indicating that the analysis results of these wavelengths are more accurate in the measurement at this time.

[0041] There are two cluster centers: If there are two cluster centers, it means that the analysis results of the weighted wavelengths deviate from the mainstream results. It may be that the interference signal of some wavelengths is affected by noise, or the wavelength is not sensitive enough to the parameter, resulting in inconsistency with the measurement results of other wavelengths. In this case, it is necessary to eliminate the inappropriate wavelengths to avoid affecting the final measurement results.

[0042] In the above way, it is possible to select wavelengths that are only sensitive to parameter i. If the data of a certain wavelength is abnormal, or the wavelength is less sensitive to a certain parameter of the film, these unreliable wavelengths can be effectively eliminated by removing the wavelengths that do not meet the criteria. This can prevent the erroneous data of these wavelengths from affecting the final measurement results and ensure the accuracy of the measurement results.

[0043] The re-measurement includes, among N different wavelengths, removing k wavelengths that do not meet the criteria, and if the number of remaining wavelengths is not less than N / 2, directly outputting the analytical results of the wavelengths that meet the criteria corresponding to the parameter i, and outputting them; if the number of remaining wavelengths is less than N / 2, randomly selecting k other wavelengths, performing interference fringe analysis and cluster selection on the re-selected wavelengths in a sliding time window, until the remaining wavelengths are not less than N / 2 after removing the wavelengths that do not meet the criteria (at least N new time windows are required after the start of the re-measurement); obtaining the analytical results of the wavelengths that meet the criteria corresponding to the parameter i, and outputting them (the purpose of this step is to make at least half of the wavelengths sensitive to the parameter i, and only using the sensitive wavelength analytical results for output). Among them, the k other wavelengths do not include the removed wavelengths; the re-selected wavelengths include the remaining wavelengths that meet the criteria and the newly added k other wavelengths.

[0044] In multi-wavelength interferometry, in order to ensure the reliability and accuracy of the results, it is necessary to rely on a sufficient number of wavelengths. If in the preliminary analysis process, after removing the wavelengths that do not meet the criteria, the number of remaining wavelengths is less than N / 2, that is, the number of remaining wavelengths is less than half, then these remaining wavelengths may not provide enough effective information for accurate measurement. Therefore, by randomly selecting other wavelengths to supplement until the number of remaining wavelengths is not less than N / 2, it is ensured that there are enough wavelengths involved in the measurement and these wavelengths can provide sufficient characteristic information, thereby improving the reliability of the final result. This step is to avoid insufficient measurement information due to inaccurate data of some wavelengths, and to ensure that accurate measurement results can be obtained from sufficient and effective wavelength data.

[0045] Furthermore, the final measurement result includes cluster selection and re-measurement for both parameters C and K; after the output is completed, cluster selection and re-measurement are performed on parameter G. When cluster selection and re-measurement of the three parameters are completed and output, the test process ends. The analytical results corresponding to the wavelengths that meet the criteria and the parameter i are averaged to obtain the final measurement result.

[0046] During multi-wavelength optical measurements, different wavelengths have different sensitivities to different parameters. By performing cluster selection and re-measurement in stages and separately, it is possible to focus on optimizing each parameter and ensure that the measurement accuracy of each parameter is optimal. Specifically, length (C) and width (K) are the planar dimensions of the film, and their measurements are directly affected by the optical interference fringes. These two parameters are usually measured on the same plane, so their measurement processes are independent of each other and do not require the interference of the thickness parameter (G). By measuring C and K jointly in the same time window and optimizing the results through clustering and re-measurement, the dimensions of these two parameters can be accurately obtained. Thickness (G) is the vertical dimension of the film and has no direct relationship with the measurement of length and width, so it should be handled separately during the measurement process. By confirming the accurate values ​​of C and K first, and then starting to measure the thickness, the change of length and width dimensions can be avoided from interfering with the thickness measurement. This ensures that the thickness measurement process is more accurate and independent of the change of the planar dimensions.

[0047] Although length, width and thickness are both dimensional parameters of thin films, their measurement processes have different optical characteristics. Length and width are plane parameters, which are affected by factors such as the angle of incidence and the distribution of interference fringes, while thickness is more dependent on the verticality of the interference fringes and the interference effect of light. Measuring them separately can prevent the change of length and width from affecting the measurement of thickness, and ensure that the measurement result of each parameter is not interfered by other parameters.

[0048] The following constraints are included in the process of randomly selecting multiple wavelengths: N>3; the maximum difference of the randomly selected multiple wavelengths is not less than E; wherein E represents the threshold value of the maximum wavelength difference.

[0049] On the other hand, this embodiment also provides a metal film size measurement system based on optical measurement, which includes: The acquisition unit irradiates the metal film with a multi-wavelength laser to generate an interference signal; The attention control unit modulates the wavelength of the incident light and adjusts the attention of different wavelengths by sliding the time window; A measuring unit, which obtains interference fringes in each time window and obtains a measurement result of each time window according to the interference fringes; The output unit performs cluster selection according to the measurement results of the time window, and remeasures using the selection results until the criterion is met to obtain the final measurement result.

[0050] If the above functions are implemented in the form of software functional units and sold or used as independent products, they can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention, or the part that contributes to the prior art, 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, including several instructions for a computer device (which can be a personal computer, server, or network device, etc.) to perform all or part of the steps of the method described in each embodiment of the present invention. The aforementioned storage medium includes: U disk, mobile hard disk, read-only memory (ROM, Read-Only Memory), random access memory (RAM, Random Access Memory), disk or optical disk, etc., which can store program code.

[0051] The logic and / or steps represented in the flowchart or otherwise described herein, for example, can be considered as an ordered list of executable instructions for implementing logical functions, and can be embodied in any computer-readable medium for use by an instruction execution system, device or apparatus (such as a computer-based system, a system including a processor, or other system that can fetch instructions from an instruction execution system, device or apparatus and execute instructions), or in conjunction with such instruction execution systems, devices or apparatuses. For the purposes of this specification, "computer-readable medium" can be any device that can contain, store, communicate, propagate or transmit a program for use by an instruction execution system, device or apparatus, or in conjunction with such instruction execution systems, devices or apparatuses.

[0052] More specific examples of computer-readable media (a non-exhaustive list) include the following: an electrical connection with one or more wires (electronic device), a portable computer disk case (magnetic device), a random access memory (RAM), a read-only memory (ROM), an erasable and programmable read-only memory (EPROM or flash memory), an optical fiber device, and a portable compact disk read-only memory (CDROM). In addition, the computer-readable medium may even be a paper or other suitable medium on which the program is printed, since the program may be obtained electronically, for example, by optically scanning the paper or other medium, followed by editing, deciphering or, if necessary, processing in another suitable manner, and then stored in a computer memory.

[0053] It should be understood that the various parts of the present invention can be implemented by hardware, software, firmware or a combination thereof. In the above-mentioned embodiments, multiple steps or methods can be implemented by software or firmware stored in a memory and executed by a suitable instruction execution system. For example, if implemented by hardware, as in another embodiment, it can be implemented by any one of the following technologies known in the art or their combination: a discrete logic circuit having a logic gate circuit for implementing a logic function for a data signal, a dedicated integrated circuit having a suitable combination of logic gate circuits, a programmable gate array (PGA), a field programmable gate array (FPGA), etc.

[0054] Example 2 is an embodiment of the present invention, which provides a metal film size measurement method based on optical measurement. In order to verify the beneficial effects of the present invention, scientific demonstration is carried out through economic benefit calculation and simulation experiments.

[0055] The dimensions of metal films were measured using the traditional single light source method, the invented method, and the standard value. The experimental objects were aluminum (Al) film, copper (Cu) film, and tin (Sn) film, with thicknesses of 100nm, 500nm, and 1000nm, respectively.

[0056] Three metal films of aluminum (Al), copper (Cu) and tin (Sn) were selected, and the film size was 10 mm × 10 mm.

[0057] The thickness of each metal film is 100nm, 500nm and 1000nm respectively.

[0058] Before the experiment, the film surface was cleaned to ensure that there were no surface contaminants.

[0059] Traditional single light source uses laser with a wavelength of 532nm.

[0060] The present invention adopts four lasers with different wavelengths (532nm, 650nm, 780nm and 980nm) to perform interference measurement, and optimizes the interference signal in combination with a weighted algorithm.

[0061] Standard values ​​are measured using known standard instruments as a reference.

[0062] Interference image acquisition: The interference fringes of the reflected light are captured using a high-resolution CCD camera.

[0063] Fourier transform and edge detection algorithm are used to extract interference fringe data.

[0064] Data processing: The traditional method directly measures the size through a single light source.

[0065] The method of the present invention generates interference signals through multi-wavelength lasers and processes them in combination with a weighted algorithm to improve measurement accuracy.

[0066] Standard values ​​are based on calibrated precision instruments that directly measure film dimensions.

[0067] Data recording and comparison: The measurement results under each method were recorded, and the differences between the invented method and the traditional single light source method and the standard value were compared, as shown in Table 1.

[0068] Table 1 Experimental data table Through the data in the table, the advantages of the present invention compared with the traditional single light source method can be analyzed from the following aspects: Measurement accuracy: For the measurement of the length (length C) and width (width K) of the film, the measurement results obtained using the multi-wavelength weighted method of the present invention (such as aluminum film: 9.87 mm, copper film: 10.03 mm, tin film: 10.07 mm) are very close to the standard values ​​(such as aluminum film: 9.90 mm, copper film: 10.05 mm, tin film: 10.09 mm), and are more accurate than the results of the traditional single light source method (such as aluminum film: 9.85 mm, copper film: 10.01 mm, tin film: 10.05 mm).

[0069] The present invention can effectively reduce the measurement error caused by a single wavelength under the weighted processing of signals of different wavelengths, especially when the film is thicker (such as 500nm and 1000nm), the advantage of multi-wavelength processing is more obvious.

[0070] Thickness measurement: In the measurement of thickness (G), the results of the traditional method at different wavelengths (such as aluminum film: 1250nm, copper film: 1275nm, tin film: 1300nm) show certain deviations, which may be due to the matching problem between the single wavelength laser and the film characteristics.

[0071] The method of the present invention obtains more consistent thickness measurement results (such as aluminum film: 1250nm, copper film: 1278nm, tin film: 1302nm) by weighting interference signals of different wavelengths. The measurement results are close to the standard values ​​(such as aluminum film: 1252nm, copper film: 1280nm, tin film: 1304nm), which proves the high accuracy of the method.

[0072] Error analysis: The traditional single light source method has a large measurement error, especially in the measurement of thicker films. For example, the copper film thickness measurement result is 1275nm, the standard value is 1280nm, and the error is 5nm. However, the error of the 1278nm result obtained by the method of the present invention and the standard value is reduced to 2nm, indicating that the method of the present invention can effectively reduce the measurement error.

[0073] Compared with traditional methods, the present invention can significantly improve the accuracy and consistency of film size measurement through multi-wavelength weighted processing and signal optimization.

[0074] Consistency and reliability of measurement: In many experiments, the measurement results of the traditional method have certain fluctuations, especially in the measurement of thicker films. In contrast, the method of the present invention makes the measurement results more consistent and the reliability is greatly improved by weighting and optimizing the multi-wavelength data.

[0075] The measurement results of the standard value are very close to the results of the method of the present invention, which shows that the present invention can achieve a measurement accuracy comparable to that of a precision instrument in practical applications.

[0076] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit it. Although the present invention has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that the technical solutions of the present invention may be modified or replaced by equivalents without departing from the spirit and scope of the technical solutions of the present invention, which should all be included in the scope of the claims of the present invention.

Claims

1. A method for measuring the size of a metal film based on optical measurement, characterized in that: include: The metal film is irradiated by a multi-wavelength laser to generate an interference signal; Modulate the wavelength of the incident light and adjust the attention of different wavelengths by sliding the time window; Obtaining interference fringes in each time window, and obtaining a measurement result of each time window based on the interference fringes; Cluster selection is performed according to the measurement results of the time window, and re-measurement is performed using the selection results to obtain the final measurement results.

2. The method for measuring the size of a metal film based on optical measurement according to claim 1, characterized in that: The multi-wavelength laser includes randomly selecting N laser sources with different wavelengths to form an incident light combination; The selected multi-wavelength laser source is irradiated onto the metal film. The laser beam interacts with the surface. A high-resolution CCD or CMOS camera is used to receive the reflected light and capture the interference images at different wavelengths to obtain the interference fringe pattern generated by each wavelength of laser.

3. The method for measuring the size of a metal film based on optical measurement according to claim 2, characterized in that: The modulation of the attention to the wavelength of the incident light includes weighting the analysis results of N different wavelengths; Randomly select a wavelength from N interference signals with different wavelengths and set it as m; After obtaining the interference fringe pattern generated by the laser of each wavelength, the interference fringe pattern corresponding to each wavelength is analyzed, and the analysis results of each wavelength are integrated; During integration, the parsing results corresponding to wavelength m are subjected to attention weighting processing; The analysis process includes obtaining the surface morphological characteristics of the film by performing surface fitting on the edge position and shape of the interference fringes; and obtaining thickness information by calculating using the spacing of the interference fringes, the thickness of the film, the refractive index, the angle of incidence, and the wavelength of the light wave.

4. The method for measuring the size of a metal film based on optical measurement according to claim 3, characterized in that: The adjusting the attention of different wavelengths by sliding the time window includes setting a fixed time window length, randomly selecting a wavelength in each time window, and performing attention weighted processing on the corresponding analysis result; The constraint when selecting the wavelength is that the selected wavelengths in N consecutive time windows are all different.

5. The method for measuring the size of a metal film based on optical measurement according to claim 4, characterized in that: The measurement result of each time window includes weighting the analysis results corresponding to N wavelengths in each time window; assuming that, represents the weight coefficient. If n corresponds to the analytical result corresponding to the unweighted wavelength, then ; If n corresponds to the analytical result corresponding to the weighted wavelength, then ; M represents a weighting coefficient, and M>2; i∈{C, K, G}, C represents the length of the metal film, K represents the width of the metal film, and G represents the thickness of the metal film; For each parameter i of the metal film, M analysis results corresponding to the weighted wavelength are copied according to the weight coefficient, and the analysis results corresponding to other N-1 wavelengths form a parameter set as the measurement result.

6. The method for measuring the size of a metal film based on optical measurement according to claim 5, characterized in that: The cluster selection according to the measurement result of the time window includes obtaining N consecutive time windows from the current time series, and performing cluster selection for each parameter i of the metal film in any time window; The cluster selection includes clustering the measurement results. If there is only one cluster center, the wavelength of the current window attention weighting is determined. For the measurement result of the metal film parameter i, Satisfy the criteria; Otherwise, the judgment does not satisfy the criterion; The re-measurement includes removing k wavelengths that do not meet the criteria from N different wavelengths, and if the number of remaining wavelengths is less than N / 2, randomly selecting k other wavelengths, and performing interference fringe analysis and cluster selection on the re-selected wavelengths in a sliding time window until the remaining wavelengths are not less than N / 2 after removing the wavelengths that do not meet the criteria; Obtain the analytical result of the wavelength that meets the criterion corresponding to the parameter i and output it; The k other wavelengths do not include the removed wavelengths; the reselected wavelengths include the remaining wavelengths that meet the criterion and the newly added k other wavelengths.

7. The method for measuring the size of a metal film based on optical measurement according to claim 6, characterized in that: The final measurement result includes cluster selection and re-measurement for both parameters C and K; after the output is completed, cluster selection and re-measurement for parameter G; When all three parameters have completed cluster selection and remeasurement and output, the test process ends; The average of the analytical results of the parameter i corresponding to the wavelengths satisfying the criterion is calculated to obtain the final measurement result; The following constraints are included in the process of randomly selecting multiple wavelengths: N>3; The maximum difference of multiple randomly selected wavelengths is not less than E; Wherein, E represents the threshold value of the maximum wavelength difference.

8. A metal film dimension measurement system based on optical measurement using the method according to any one of claims 1 to 7, characterized in that: The acquisition unit irradiates the metal film with a multi-wavelength laser to generate an interference signal; The attention control unit modulates the wavelength of the incident light and adjusts the attention of different wavelengths by sliding the time window; A measuring unit, which obtains interference fringes in each time window and obtains a measurement result of each time window according to the interference fringes; The output unit performs cluster selection according to the measurement results of the time window, and remeasures using the selection results until the criterion is met to obtain the final measurement result.

9. A computer device comprising: A memory and a processor; the memory stores a computer program, wherein the processor implements the steps of any method as claimed in claim 1 when executing the computer program.

10. A computer-readable storage medium having a computer program stored thereon, characterized in that: When the computer program is executed by a processor, the steps of the method according to any one of claims 1 to 7 are implemented.

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