Focusing Method, Focusing System, Device, and Storage Medium of an Optical Device

Abstract

A focusing method for an optical device, a focusing system, a device, and a storage medium, wherein the optical device includes a spectrum collector, and the focusing method includes: obtaining a reference spectrum; collecting test spectra of an object to be tested at different test focus heights through the spectrum collector; obtaining spectral fitting parameter values for each of the test spectra and the reference spectrum, wherein the spectral fitting parameter values are positively correlated or negatively correlated with the error value between the test spectrum and the reference spectrum; and extracting, based on the spectral fitting parameter values, a test focus height corresponding to the spectral fitting parameter value that minimizes the error value as a first in-focus height. The present invention uses the spectral fitting parameter values of the spectral data to determine whether the object to be tested is in focus, thereby performing focus adjustment. Therefore, it is possible to improve focusing efficiency while ensuring focusing accuracy without adding additional hardware modules (e.g., a focus detection module).

Description

Technical Field

[0001] Embodiments of the present invention relate to the field of optical detection technology, and in particular to a focusing method, a focusing system, a device, and a storage medium for an optical device. Background Art

[0002] In the field of optical inspection, focusing accuracy often directly impacts measurement precision. For example, film thickness measurement equipment is extremely sensitive to in-focus height during measurement, requiring high-precision focus height measurements to avoid errors. Focusing speed, on the other hand, directly impacts measurement efficiency; excessively long focusing times can lead to reduced efficiency.

[0003] One current approach is to install a focus detection module within the optical device, using it to measure the height of the object's surface and then achieve focus based on this height data. However, this method results in low measurement efficiency and difficulty significantly improving measurement accuracy. Furthermore, the configuration of the focus detection module leads to higher costs and a more complex overall system. Summary of the Invention

[0004] The problem solved by the embodiments of the present invention is to provide a focusing method, a focusing system, a device and a storage medium for an optical device, which improve the focusing efficiency while ensuring the focusing accuracy.

[0005] To solve the above problems, an embodiment of the present invention provides a focusing method for an optical device, wherein the optical device includes a spectrum collector, and the focusing method includes: obtaining a reference spectrum; collecting test spectra of the object to be tested at different test focusing heights through the spectrum collector; obtaining spectral fitting parameter values of each of the test spectra and the reference spectrum, wherein the spectral fitting parameter values are positively correlated or negatively correlated with the error values between the test spectrum and the reference spectrum; and according to the spectral fitting parameter values, extracting the test focusing height corresponding to the spectral fitting parameter value that minimizes the error value as the first in-focus height.

[0006] Correspondingly, an embodiment of the present invention also provides a focusing system for an optical device, comprising: a reference spectrum acquisition module for acquiring a reference spectrum; a spectrum collector for acquiring test spectra of the object to be tested at different test focusing heights; a calculation module for obtaining spectral fitting parameter values of each of the test spectra and the reference spectrum, the spectral fitting parameter values being positively correlated or negatively correlated with the error values between the test spectrum and the reference spectrum; and a data processing module for extracting, based on the spectral fitting parameter values, the test focusing height corresponding to the spectral fitting parameter value that minimizes the error value, as the first in-focus height.

[0007] Accordingly, an embodiment of the present invention also provides a device comprising at least one memory and at least one processor, wherein the memory stores one or more computer instructions, wherein the one or more computer instructions are executed by the processor to implement the focusing method described in the embodiment of the present invention.

[0008] Correspondingly, an embodiment of the present invention further provides a storage medium, wherein the storage medium stores one or more computer instructions, and the one or more computer instructions are used to implement the focusing method described in the embodiment of the present invention.

[0009] Compared with the prior art, the technical solution of the embodiment of the present invention has the following advantages:

[0010] In the focusing method of an optical device provided by an embodiment of the present invention, by obtaining a reference spectrum and a test spectrum of the object to be tested at different test focusing heights, and obtaining spectral fitting parameter values corresponding one-to-one to the test focusing heights, the test focusing height corresponding to the spectral fitting parameter value that minimizes the error value is extracted as the first in-focus height. The embodiment of the present invention directly uses the spectral fitting parameter (Goodness of Fit, GOF) value of the spectral data to determine whether the object to be tested is in focus, thereby adjusting the focus of the object to be tested. Therefore, the embodiment of the present invention can improve the focusing efficiency while ensuring the focusing accuracy without adding additional hardware modules (for example, a focus detection module).

[0011] In the focusing system of the optical device provided by an embodiment of the present invention, a reference spectrum acquisition module and a spectrum collector are used to respectively acquire a reference spectrum and a test spectrum of the object to be tested at different test focusing heights, and after using a calculation module to obtain spectrum fitting parameter values corresponding one-to-one to the test focusing heights, a data processing module is used to extract the test focusing height corresponding to the spectrum fitting parameter value that minimizes the error value, as the first in-focus height. The embodiment of the present invention directly uses the GOF value of the spectral data to determine whether the object to be tested is in focus, thereby adjusting the focus of the object to be tested. Therefore, the embodiment of the present invention can improve the focusing efficiency while ensuring the focusing accuracy without adding additional hardware modules (for example, a focus detection module). BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 is a flow chart of an embodiment of a focusing method for an optical device of the present invention;

[0013] Figure 2 yes Figure 1 A schematic diagram of an embodiment of step S2;

[0014] Figure 3 yes Figure 1 A schematic diagram of an embodiment of step S5;

[0015] Figure 4 is a functional block diagram of an embodiment of a focusing system of an optical device of the present invention;

[0016] Figure 5 This is a hardware structure diagram of a device provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0017] As can be seen from the background art, in current focusing methods, it is difficult to improve focusing efficiency while ensuring focusing accuracy.

[0018] In order to solve the technical problem, an embodiment of the present invention provides a focusing method for an optical device, wherein the optical device includes a spectrum collector, and the focusing method includes: obtaining a reference spectrum; collecting a test spectrum of the object to be tested at different test focusing heights through the spectrum collector; obtaining a spectrum fitting parameter value of each of the test spectra and the reference spectrum, wherein the spectrum fitting parameter value is positively correlated or negatively correlated with the error value between the test spectrum and the reference spectrum; and according to the spectrum fitting parameter value, extracting the test focusing height corresponding to the spectrum fitting parameter value that minimizes the error value as the first in-focus height.

[0019] In the focusing method provided by an embodiment of the present invention, by obtaining a reference spectrum and a test spectrum of the object to be tested at different test focusing heights, and obtaining the spectrum fitting parameter values corresponding one-to-one to the test focusing heights, the test focusing height corresponding to the spectrum fitting parameter value that minimizes the error value is extracted as the first in-focus height. The embodiment of the present invention directly uses the GOF value of the spectral data to determine whether the object to be tested is in focus, thereby adjusting the focus of the object to be tested. Therefore, the embodiment of the present invention can improve the focusing efficiency while ensuring the focusing accuracy without adding additional hardware modules (for example, a focusing detection module).

[0020] refer to Figure 1 , which shows a flow chart of an embodiment of a focusing method of an optical device of the present invention.

[0021] In this embodiment, the optical device includes a spectrum collector, and the focusing method of the optical device includes the following basic steps:

[0022] Step S1: obtaining a reference spectrum;

[0023] Step S5: collecting the test spectra of the object to be tested at different test focus heights by the spectrum collector;

[0024] Step S6: obtaining spectrum fitting parameter values of each of the test spectra and the reference spectrum, wherein the spectrum fitting parameter values are positively correlated or negatively correlated with the error values between the test spectrum and the reference spectrum;

[0025] Step S7: extracting, based on the spectrum fitting parameter value, a test focus height corresponding to the spectrum fitting parameter value that minimizes the error value as a first in-focus height.

[0026] It should be noted that the focusing method further includes: Step S2: determining a spectrum acquisition reference position, where the spectrum acquisition reference position has a reference focusing height.

[0027] The focusing method further includes: step S3: determining a focusing height range and a preset moving step, wherein the focusing height range has a minimum focusing height and a maximum focusing height, and any one of the minimum focusing height and the maximum focusing height is used as an initial focusing height.

[0028] The focusing method further includes: step S4: placing the object to be tested, and placing the object to be tested at the spectrum collection reference position.

[0029] The focusing method further includes: step S8: relatively moving the object to be measured and the detection module to a position at the second in-focus height, and maintaining the object to be measured and the detection module at the position at the second in-focus height.

[0030] The focusing method further includes: step S9: after the object to be tested and the detection module are kept at the second in-focus height, the object to be tested is detected by the detection module.

[0031] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, specific embodiments of the present invention are described in detail below with reference to the accompanying drawings.

[0032] In this embodiment, the focusing method of the optical device 900 is used to obtain a first in-focus height of the object to be detected before the object to be detected, thereby improving detection accuracy.

[0033] Therefore, if Figure 2 As shown, the optical device 900 includes a spectrum collector, which is used to collect the spectrum of the object to be measured. In this embodiment, the spectrum collector includes an ellipsometer, a reflection spectrometer, or a spectroscopic scatterometer. As an example, the spectrum collector is an ellipsometer.

[0034] Specifically, if Figure 2 As shown, the optical device 900 is integrated into a detection device, and the detection device further includes a stage 800. The stage 800 is used to carry the object to be detected.

[0035] refer to Figure 1 , execute step S1 to obtain a reference spectrum.

[0036] The focusing method is used to obtain a first in-focus height of the object under test, with the reference spectrum serving as a comparison benchmark for subsequent acquisitions of the first in-focus height. Specifically, after subsequently acquiring test spectra of the object under test at different test focus heights, spectrum fitting parameter values are obtained for each of the test spectra corresponding to the test focus heights and the reference spectrum, thereby extracting the test focus height corresponding to the spectrum fitting parameter value that minimizes the error value as the first in-focus height.

[0037] In this embodiment, the reference spectrum is obtained based on the physical parameters of the object to be measured and the theoretical model. In other words, the reference spectrum is theoretical spectrum data.

[0038] Specifically, the step of obtaining the reference spectrum includes: providing a theoretical model of the interaction between the sample and light, the theoretical model being used to represent the relationship between the spectrum of the outgoing light after the light acts on the sample and the physical parameters of the sample; using the physical parameters of the object to be measured as the physical parameters of the sample, and obtaining the outgoing light spectrum according to the theoretical model, which is used as the reference spectrum.

[0039] That is, the physical parameters of the object to be measured are substituted into the theoretical model, so as to obtain the emission light spectrum corresponding to the object to be measured according to the theoretical model as the reference spectrum.

[0040] It should be noted that, in the step of obtaining the reference spectrum, the sample is the same as the object to be measured, so that the reference spectrum of the object to be measured can be obtained.

[0041] Continue to refer Figure 1 The focusing method further includes: executing step S3: determining the focusing height range H range and preset moving step length, the focusing height range H range With minimum focusing height H upper and maximum focusing height H lower , the minimum focusing height H upper and maximum focusing height H lower Any one of the focus heights is used as the initial focus height.

[0042] Determine the focusing height range H range The preset moving step length is used to prepare for subsequent multiple spectrum acquisition and processing of the object to be measured. It should be noted that the focusing height refers to the relative height between the optical device 900 and the object to be measured.

[0043] In this embodiment, starting from the initial focus height position, within the focus height range H range The focus position is changed according to the preset moving step length to collect the test spectrum of the object under test at different focus heights. Moreover, the minimum focus height Hupper and maximum focusing height H lower Any one of the focus heights is used as the initial focus height, and accordingly, the subsequent focus heights from the maximum focus height H lower Gradually change the focus position to the minimum focus height H upper , or, from the minimum focusing height H upper Gradually change the focus position to the maximum focus height H upper position, thereby helping to reduce focusing complexity.

[0044] In this embodiment, according to the reference focusing height H ref , determine the focusing height range H range , the reference focusing height H ref Located in the focusing height range H range That is, by making the reference focusing height H ref Positive and negative offset preset heights to obtain the focus height range H range .

[0045] By focusing at the reference height H ref Based on the positive and negative offset preset height, to obtain the focus height range H range , which is beneficial to increase the focusing height range H range The accuracy makes it easy to focus in the height range H range A first in-focus height of the object to be measured is obtained.

[0046] It should be noted that the preset height should not be too small or too large. If the preset height is too small, the focusing height range H range The corresponding is too small, which easily leads to difficulty in focusing within the focusing height range H range If the preset height is too large, the focus height range H range The corresponding value is too large, which leads to excessive times of subsequent spectral acquisition and processing, and accordingly leads to excessive amount of data to be processed, which in turn leads to a decrease in focusing efficiency.

[0047] Therefore, in this embodiment, the preset height is 0.05 mm to 0.1 mm. That is, the minimum focusing height H upper With reference focusing height H ref The difference is -0.05 mm to -0.1 mm, the maximum focusing height H lower With reference focusing height H ref The difference is 0.05 mm to 0.1 mm. Wherein, along the focusing direction, the minimum focusing height H upper Smaller than the reference focusing height H ref, the maximum focusing height H lower Greater than the reference focusing height H ref .

[0048] It should also be noted that the preset movement step size should not be too small or too large. If the preset movement step size is too small, the subsequent spectral acquisition process will be too frequent, which will lead to a decrease in focusing efficiency. If the preset movement step size is too large, the subsequent spectral acquisition process will be too few, resulting in too little collected data, which can easily reduce focusing accuracy. To this end, in this embodiment, the preset movement step size is 0.5 microns to 20 microns. For example, the preset movement step size is 1 micron, 5 microns, or 10 microns.

[0049] Combined with reference Figure 1 and Figure 2 , Figure 2 yes Figure 1 Schematic diagram of an embodiment of step S2 in the embodiment, before determining the focusing height range, the focusing method further includes: executing step S2, determining a spectrum acquisition reference position, the spectrum acquisition reference position having a reference focusing height H ref .

[0050] Subsequently, the focus height range is determined based on the spectrum acquisition reference position; in addition, the spectrum acquisition reference position can also be used to define the initial position for placing the object to be measured subsequently.

[0051] It should be noted that the object to be tested is usually formed on a product substrate. Therefore, before placing the product substrate with the object to be tested, the spectrum acquisition reference position is determined so that the object to be tested can be focused and detected in sequence after being placed.

[0052] In this embodiment, a reference substrate 300 identical to the product substrate is used to determine the spectrum acquisition reference position. Specifically, the step of determining the spectrum acquisition reference position includes: placing the reference substrate 300, which is identical to the product substrate; obtaining the in-focus height of the reference substrate 300 as the spectrum acquisition reference position. Accordingly, the focus height corresponding to the spectrum acquisition reference position is the reference focus height H. ref .

[0053] Since the object under test 200 is formed on the product substrate 100, there is a height difference between the surface of the object under test 200 and the surface of the product substrate 100, which results in a difference in the in-focus height between the surface of the object under test 200 and the surface of the product substrate 100. The difference in in-focus height is affected by the height difference between the surface of the object under test 200 and the surface of the product substrate 100. Therefore, by selecting a reference substrate 300 that is the same as the product substrate 100 and obtaining the in-focus height of the reference substrate 300, it is helpful to obtain a more accurate focus height range H. range , so that it can be faster and more accurate from the focus height range H range A first in-focus height of the object under test 200 is obtained.

[0054] Therefore, in this embodiment, after determining the spectrum acquisition reference position, according to the reference focusing height H ref , determine the focus height range H range , the reference focusing height H ref Located in the focusing height range H range Inside.

[0055] In this embodiment, in the step of placing the reference substrate 300 , the reference substrate 300 is placed on the stage 800 .

[0056] It should be noted that, since the focusing and detection of the object 200 are performed sequentially after the object 200 is subsequently placed, in this embodiment, the reference base 300 is first used to determine the spectrum acquisition reference position before the object 200 is placed.

[0057] Continue to refer Figure 1 , executing step S4, placing the object to be tested 200, and placing the object to be tested 200 at the spectrum collection reference position.

[0058] The object under test 200 is placed to prepare for subsequent focusing and testing of the object under test 200. Furthermore, by first placing the object under test 200 at the spectrum acquisition reference position, the focus position can be changed based on the spectrum acquisition reference position, thereby acquiring test spectra of the object under test at different test focus heights.

[0059] In this embodiment, the step of placing the object to be tested 200 includes placing a product substrate 100 on which the object to be tested 200 is formed. Specifically, the step of placing the object to be tested 200 includes placing the product substrate 100 on which the object to be tested 200 is formed on the stage 800 .

[0060] As an example, the product substrate 100 is a wafer. In this embodiment, the object to be tested 200 is a film layer to be tested.

[0061] In this embodiment, the object to be measured 200 is placed at the reference position for spectrum collection, that is, the reference focusing height H ref at the location.

[0062] Combined with reference Figure 1 and Figure 3 , Figure 3 yes Figure 1 Execute step S5: collect the test spectra of the object to be tested 200 at different test focus heights by the spectrum collector.

[0063] The test spectra are then used to obtain spectral fitting parameter values for each test spectrum and the reference spectrum, thereby obtaining spectral fitting parameter values that correspond one-to-one to the test focus heights. Accordingly, the test focus height corresponding to the spectral fitting parameter value that minimizes the error is subsequently extracted as the first in-focus height. Therefore, this embodiment directly uses the fitting parameter values of the spectral data to determine whether the object under test 200 is in focus, thereby adjusting the focus of the object under test 200. This improves focusing efficiency while maintaining focusing accuracy without adding additional hardware modules (e.g., a focus detection module).

[0064] Specifically, the steps of collecting the test spectrum of the object under test 200 at different test focus heights by the spectrum collector include: starting from the initial focus height position, in the focus height range H range The focus position is changed according to a preset moving step length, so that the object under test 200 and the optical device 900 are relatively moved to positions of different test focus heights, and test spectra of the object under test 200 at different test focus heights are collected.

[0065] That is, by performing multiple spectrum acquisition processes, the test spectra of the object under test at different test focus heights are obtained. In the first spectrum acquisition process, the test focus height is the initial focus height, and the test focus height of the subsequent spectrum acquisition process is the height of the test focus height of the previous spectrum acquisition process after changing the preset moving step. Moreover, the minimum focus height H upper and maximum focusing height H lower Any of the focus heights in is used as the initial focus height, and accordingly, the test focus height of the last spectrum acquisition process is the minimum focus height H upper and maximum focusing height H lower Another focus height in .

[0066] Based on the detection principle, detection is performed through the collected spectrum of the surface of the object to be tested 200. Therefore, using the spectrum fitting parameter value to obtain the first in-focus height is conducive to improving the credibility of the data, thereby improving the focusing accuracy.

[0067] In this embodiment, since the spectrum is obtained by collecting the reflectivity of the surface of the object under test 200, the test spectrum includes a curve of preset parameters and wavelength, wherein the preset parameters are related to the reflectivity. Specifically, the preset parameters include phase, amplitude, phase sine, or phase negative sine. The phase sine and phase negative sine are trigonometric function conversions of the phase, thereby normalizing the data during data fitting, making it easier to calculate the spectrum fitting parameter values.

[0068] It should be noted that, during the focusing process, appropriate types of preset parameters can be selected for fitting according to actual needs (for example, according to the different products to be tested), so as to achieve fast convergence and high accuracy.

[0069] In this embodiment, the test spectrum is collected by the spectrum collector of the optical device 900 .

[0070] It should be noted that, in the step of placing the object to be tested 200, the object to be tested 200 is placed at the reference position for spectrum acquisition, that is, the reference focusing height H ref Position, therefore, the step of collecting the test spectrum for the first time includes: from the spectrum collection reference position, along the focusing direction, relatively moving the object to be tested 200 and the optical device 900 to the initial focusing height position.

[0071] It should also be noted that the focusing height is the distance between the object to be tested 200 and the objective lens of the optical device 900. Therefore, in the process of collecting test spectra of the object to be tested 200 at different test focusing heights, changing the focusing position is to change the distance between the object to be tested 200 and the objective lens of the optical device 900. Therefore, the step of collecting the test spectra of the object to be tested 200 at different test focusing heights by the spectrum collector includes: fixing the position of the spectrum collector and moving the object to be tested 200 along the focusing direction to move the object to be tested 200 and the optical device 900 relative to each other to positions with different test focusing heights; or fixing the position of the object to be tested 200 and moving the spectrum collector along the focusing direction to move the object to be tested 200 and the optical device 900 relative to each other to positions with different test focusing heights.

[0072] That is, while the position of the spectrum collector is fixed, the focus height is adjusted by moving the object under test 200 along the focus direction. Similarly, while the position of the object under test 200 is fixed, the focus height is adjusted by moving the spectrum collector along the focus direction. Fixing the position of the spectrum collector or the object under test 200 simplifies changing the focus position. In other embodiments, during each test spectrum acquisition step, the spectrum collector and the object under test can be moved simultaneously to change the focus position.

[0073] Continue to refer Figure 1 , executing step S6, obtaining spectral fitting parameter values of each of the test spectra and the reference spectrum, wherein the spectral fitting parameter values are positively correlated or negatively correlated with the error values between the test spectrum and the reference spectrum.

[0074] Subsequently, the spectrum fitting parameter value is used to determine whether the object to be measured 200 is in focus, thereby adjusting the focus of the object to be measured 200.

[0075] In this embodiment, depending on the calculation method (i.e., algorithm) for the spectrum fitting parameter values, the spectrum fitting parameter values may be positively correlated with the error value between the test spectrum and the reference spectrum, or negatively correlated with the error value between the test spectrum and the reference spectrum. Specifically, the step of obtaining the spectrum fitting parameter values includes: calculating the error value between each test spectrum and the reference spectrum; and obtaining the spectrum fitting parameter value corresponding to the test focus height based on the error value.

[0076] In this embodiment, the spectrum fitting parameter value is negatively correlated with the error value. As an example, the relationship between the spectrum fitting parameter value and the error value is GOF=exp(-rmse), or GOF=rmse -1 , where GOF is the spectral fitting parameter value, and rmse is the error value. Therefore, a larger spectral fitting parameter value indicates a smaller error between the test spectrum and the reference spectrum, and the closer the test spectrum is to the reference spectrum, the better the focus. Conversely, a smaller spectral fitting parameter value indicates a worse focus.

[0077] In other embodiments, the spectral fitting parameter value is positively correlated with the error value, and the relationship between the spectral fitting parameter value and the error value is GOF = exp(rmse), or GOF = rmse, where GOF is the spectral fitting parameter value and rmse is the error value. Accordingly, when the spectral fitting parameter value and the error value are positively correlated, a larger GOF value indicates a worse focus condition, and vice versa, a smaller GOF value indicates a better focus condition.

[0078] In this embodiment, the relationship of the error value includes:

[0079] or

[0080] Wherein, rmse is the error value, ΔI is the square or absolute value of the difference between the preset parameter values of the test spectrum and the reference spectrum, and λ is the wavelength of the test spectrum and the reference spectrum.

[0081] It should be noted that a suitable type of relationship can be selected to calculate the error value according to actual needs (for example, according to different products to be tested).

[0082] It should also be noted that, as an example, after each test spectrum is acquired, spectral fitting parameter values are obtained for the test spectrum corresponding to the test focus height and the reference spectrum. In other words, the steps of acquiring test spectra and acquiring spectral fitting parameter values are performed alternately. In other embodiments, after acquiring test spectra of the object under test at various test focus heights, spectral fitting parameter values for each test spectrum corresponding to each test focus height and the reference spectrum may be obtained.

[0083] Continue to refer Figure 1 , executing step S7, extracting, according to the spectrum fitting parameter value, the test focus height corresponding to the spectrum fitting parameter value that minimizes the error value as the first in-focus height.

[0084] As can be seen from the foregoing description, the spectral fitting parameter value can characterize the quality of the focus condition. Therefore, by extracting the test focus height corresponding to the spectral fitting parameter value that minimizes the error value, the optimal test focus height is obtained. This test focus height is referred to as the first focus height. Accordingly, during subsequent actual testing of the object under test 200, the higher spectral fitting parameter value at this first focus height facilitates improved testing accuracy of the object under test 200. For example, the reliability of the film thickness obtained by the test is higher.

[0085] In this embodiment, the spectrum fitting parameter value is negatively correlated with the error value. Therefore, based on the spectrum fitting parameter value, extracting the test focus height corresponding to the spectrum fitting parameter value that minimizes the error value as the first in-focus height includes: obtaining the test focus height corresponding to the maximum spectrum fitting parameter value as the first in-focus height. When the spectrum fitting parameter value is negatively correlated with the error value, a larger spectrum fitting parameter value indicates a smaller error between the test spectrum and the reference spectrum, a closer the test spectrum is to the reference spectrum, and accordingly, a better in-focus condition. Conversely, a smaller spectrum fitting parameter value indicates a worse in-focus condition. Therefore, the test focus height corresponding to the maximum spectrum fitting parameter value is obtained as the first in-focus height.

[0086] In other embodiments, the spectrum fitting parameter value is positively correlated with the error value. Accordingly, the step of extracting, based on the spectrum fitting parameter value, the test focus height corresponding to the spectrum fitting parameter value that minimizes the error value as the first in-focus height includes: obtaining the test focus height corresponding to the minimum spectrum fitting parameter value as the first in-focus height. When the spectrum fitting parameter value is positively correlated with the error value, a larger spectrum fitting parameter value indicates a worse in-focus condition, and vice versa, a smaller spectrum fitting parameter value indicates a better in-focus condition. Therefore, the test focus height corresponding to the minimum spectrum fitting parameter value is obtained as the first in-focus height.

[0087] It should be noted that the optical device 900 further includes a detection module. The detection module is used to detect the object to be detected 200.

[0088] In this embodiment, the detection module has a second in-focus height, and there is a preset distance between the second in-focus height and the first in-focus height, and the preset distance is zero or non-zero.

[0089] It should be noted that, through pre-design, the difference in in-focus height between the detection module and the spectrum collector is typically known. Therefore, once the first in-focus height of the spectrum collector is obtained, the second in-focus height of the detection module can be obtained. Specifically, the preset distance is zero or non-zero, that is, the first in-focus height and the second in-focus height can be equal or unequal.

[0090] Therefore, continue to refer to Figure 1 The focusing method further includes: executing step S8, moving the object to be tested 200 and the detection module relative to each other to the position of the second in-focus height, and keeping the object to be tested 200 and the detection module at the position of the second in-focus height.

[0091] By relatively moving the object under test 200 and the detection module to the second in-focus height and maintaining them at the second in-focus height, preparations are made for subsequent actual testing of the object under test 200. For example, when measuring the film thickness of the object under test 200, it is necessary to measure different positions of the object under test 200. By maintaining the object under test 200 and the optical device 900 at the second in-focus height, measurements can be performed at different positions of the object under test 200 based on the second in-focus height, thereby increasing the reliability of the film thickness data obtained by the measurements.

[0092] Continue to refer Figure 1The focusing method further includes: executing step S9: after the object to be tested 200 and the detection module are kept at the second in-focus height, the object to be tested is detected by the detection module.

[0093] According to the detection requirements, the object to be tested 200 is tested, thereby achieving defect detection, film thickness detection, or line width (CD) detection of the object to be tested 200.

[0094] In this embodiment, description is made by taking the example that the first in-focus height and the second in-focus height are equal.

[0095] As an example, in the step of testing the object to be tested, the geometric dimensions of the object to be tested 200 are obtained based on the test spectrum corresponding to the first in-focus height. As an example, the object to be tested is a film to be tested, and therefore, the geometric dimensions include the thickness or line width of the film to be tested.

[0096] In other embodiments, depending on the type of the object to be detected, it can also be used to detect and obtain other types of geometric dimensions. In other embodiments, it is not limited to detecting based on the test spectrum, and other detection methods can also be used for detection.

[0097] Accordingly, an embodiment of the present invention further provides a focusing system for an optical device. Figure 4 , shows a functional block diagram of an embodiment of a focusing system of an optical device of the present invention.

[0098] The focusing system of the optical device includes: a reference spectrum acquisition module 10, used to obtain a reference spectrum; a spectrum collector 50, used to collect test spectra of the object to be tested at different test focusing heights; a calculation module 60, used to obtain spectral fitting parameter values of each of the test spectra and the reference spectrum, wherein the spectral fitting parameter values are positively correlated or negatively correlated with the error value between the test spectrum and the reference spectrum; and a data processing module 70, used to extract, based on the spectral fitting parameter values, the test focusing height corresponding to the spectral fitting parameter value that minimizes the error value as the first in-focus height.

[0099] In the focusing system, the reference spectrum acquisition module 10 and the spectrum collector 50 are used to respectively acquire the reference spectrum and the test spectrum of the object to be tested at different test focusing heights, and the calculation module 60 is used to obtain the spectrum fitting parameter values corresponding to the test focusing heights. Then, the data processing module 6070 extracts the test focusing height corresponding to the maximum spectrum fitting parameter value that minimizes the error value as the first in-focus height. This embodiment directly uses the GOF value of the spectral data to determine whether the object to be tested is in focus, thereby adjusting the focus of the object to be tested. Therefore, the embodiment of the present invention can improve the focusing efficiency while ensuring the focusing accuracy without adding additional hardware modules (for example, a focusing detection module).

[0100] The focusing system of the optical device is used to obtain a first in-focus height of the object under test before testing it, thereby improving detection accuracy. Therefore, the focusing system includes a spectrum collector 50, which is used to collect the spectrum of the object under test. In this embodiment, the spectrum collector includes an ellipsometer, a reflectance spectrometer, or a spectroscopic scatterometer. As an example, the spectrum collector is an ellipsometer.

[0101] In this embodiment, the focusing system further includes a focusing height adjustment module 40 for adjusting the focusing position.

[0102] In this embodiment, the optical device is integrated into a detection device, and the detection device further includes a stage. The stage is used to carry the object to be detected.

[0103] The reference spectrum acquisition module 10 is used to acquire a reference spectrum, wherein the reference spectrum is used as a comparison benchmark when acquiring the first in-focus height of the object to be measured.

[0104] Specifically, after using the spectrum collector 50 to obtain the test spectrum of the object to be tested at different test focusing heights, the calculation module 60 is used to obtain the spectrum fitting parameter values of the test spectrum corresponding to the test focusing heights and the reference spectrum, so that the data processing module 70 can be used to extract the test focusing height corresponding to the spectrum fitting parameter value that minimizes the error value as the first in-focus height.

[0105] In this embodiment, the reference spectrum acquisition module 10 acquires the reference spectrum based on the physical parameters of the object to be measured and a theoretical model. The reference spectrum is theoretical spectrum data. Specifically, the reference spectrum acquisition module 10 includes: a model providing unit (not shown), which is used to provide a theoretical model of the interaction between the sample and light, wherein the theoretical model is used to represent the relationship between the spectrum of the outgoing light after the light interacts with the sample and the physical parameters of the sample; and a spectrum output unit, which is used to use the physical parameters of the object to be measured as the physical parameters of the sample and obtain the outgoing light spectrum according to the theoretical model to serve as the reference spectrum.

[0106] That is, the physical parameters of the object to be measured are substituted into the theoretical model, so as to obtain the emission light spectrum corresponding to the object to be measured according to the theoretical model as the reference spectrum.

[0107] It should be noted that the sample is the same as the object to be measured, so that a reference spectrum of the object to be measured can be obtained.

[0108] In this embodiment, the focusing system further includes: a reference position determining module 20, configured to determine a spectrum collection reference position, where the spectrum collection reference position has a reference focusing height.

[0109] The reference focusing height is used to determine the focusing height range; in addition, the spectrum acquisition reference position can also be used to define the initial position for subsequently placing the object to be measured.

[0110] It should be noted that the object to be tested is usually formed on a product substrate. Therefore, the reference position determination module 20 is used to determine the spectrum acquisition reference position before placing the product substrate on which the object to be tested is formed, so that the object to be tested can be focused and detected in sequence after being placed.

[0111] In this embodiment, the reference position determination module 20 uses a reference substrate identical to the product substrate to determine the spectrum acquisition reference position. Specifically, after placing the reference substrate on the stage, the reference position determination module 20 is configured to obtain the in-focus height of the reference substrate as the spectrum acquisition reference position. Accordingly, the focus height corresponding to the spectrum acquisition reference position is the reference focus height.

[0112] Because the object under test is formed on a product substrate, there is a height difference between the surface of the object under test and the surface of the product substrate. This results in a difference in the in-focus height between the surface of the object under test and the surface of the product substrate. This difference in in-focus height is affected by the height difference between the surface of the object under test and the surface of the product substrate. Therefore, by selecting a reference substrate identical to the product substrate and obtaining the in-focus height of the reference substrate, a more accurate focus height range can be obtained, allowing the first in-focus height of the object under test to be determined more quickly and accurately within the focus height range.

[0113] Since focusing and detecting the object to be tested are performed sequentially after the object to be tested is placed, in this embodiment, the reference position determining module 20 is used to determine the spectrum acquisition reference position before the object to be tested is placed.

[0114] In this embodiment, the focusing system also includes: an initialization module 30, which is used to determine a focusing height range and a preset moving step, wherein the focusing height range has a minimum focusing height and a maximum focusing height, and any one of the minimum focusing height and the maximum focusing height is used as the initial focusing height.

[0115] The initialization module 30 determines the focus height range and the preset moving step length, in preparation for subsequent multiple spectrum acquisition and processing of the object to be measured. It should be noted that the focus height refers to the relative height between the optical device and the object to be measured.

[0116] Specifically, starting from the initial focus height position, the focus position is subsequently changed according to the preset movement step size within the focus height range to collect test spectra of the object under test at different focus heights. Moreover, either the minimum focus height or the maximum focus height is used as the initial focus height, and accordingly, the focus position is subsequently gradually changed from the maximum focus height to the minimum focus height, or vice versa, thereby facilitating reduced focusing complexity.

[0117] In this embodiment, the initialization module 30 is used to determine a focus height range based on the reference focus height, and the reference focus height is within the focus height range. In other words, the focus height range is obtained by positively or negatively offsetting the reference focus height by a preset height.

[0118] It should be noted that the preset height should not be too small or too large. If the preset height is too small, the focus height range will be too small, making it difficult to obtain the first in-focus height of the object under test within the focus height range. If the preset height is too large, the focus height range will be too large, resulting in an excessive number of subsequent spectral acquisition and processing times, resulting in an excessive amount of data to be processed, and thus a decrease in focusing efficiency.

[0119] To this end, in this embodiment, the preset height is 0.05 mm to 0.1 mm. That is, the difference between the minimum focus height and the reference focus height is -0.05 mm to -0.1 mm, and the difference between the maximum focus height and the reference focus height is 0.05 mm to 0.1 mm. Along the focusing direction, the minimum focus height is less than the reference focus height, and the maximum focus height is greater than the reference focus height.

[0120] It should be noted that the preset movement step size should not be too small or too large. If the preset movement step size is too small, the subsequent spectral acquisition and processing times will be excessive, which will lead to a decrease in focusing efficiency. If the preset movement step size is too large, the subsequent spectral acquisition and processing times will be too few, resulting in too little collected data, which will easily reduce focusing accuracy. To this end, in this embodiment, the preset movement step size is 0.5 microns to 20 microns. For example, the preset movement step size is 1 micron, 5 microns, or 10 microns.

[0121] The stage is used to carry the object under test when focusing or detecting the object under test. Specifically, the object under test is placed at the spectrum acquisition reference position, that is, at the reference focusing height, through the stage.

[0122] The object to be tested is first placed at the spectrum acquisition reference position so that the focus position can be changed based on the spectrum acquisition reference position, thereby acquiring test spectra of the object to be tested at different test focus heights. Specifically, the stage is used to support the product substrate on which the object to be tested is formed.

[0123] As an example, the product substrate is a wafer. In this embodiment, the object to be tested is a film layer to be tested.

[0124] Through the interaction between the spectrum collector 50 and the calculation module 60, the spectral fitting parameter values of each test spectrum and the reference spectrum are obtained, so that the test focus height corresponding to the spectral fitting parameter value that minimizes the error value can be subsequently extracted as the first in-focus height. Therefore, this embodiment directly uses the fitting parameter values of the spectral data to determine whether the object under test is in focus, thereby adjusting the focus of the object under test. This can improve focusing efficiency while maintaining focusing accuracy without adding additional hardware modules (such as a focus detection module).

[0125] In this embodiment, the spectrum collector 50 changes the focus position according to the preset moving step length within the focus height range from the initial focus height position, so that the object to be tested and the optical device are relatively moved to positions of different test focus heights, and the test spectra of the object to be tested at different test focus heights are collected. In other words, the spectrum collector 50 performs multiple spectrum collection processes to obtain the test spectra of the object to be tested at different test focus heights. In the first spectrum collection process, the test focus height is the initial focus height, and the test focus height of the subsequent spectrum collection process is the height of the test focus height of the previous spectrum collection process after changing the preset moving step length. Moreover, any one of the minimum focus height and the maximum focus height is used as the initial focus height, and accordingly, the test focus height of the last spectrum collection process is the other of the minimum focus height and the maximum focus height.

[0126] Specifically, during each test spectrum acquisition process, the focus height adjustment module 40 is used to adjust the focus position, so that the object to be tested and the optical device are relatively moved to positions with different test focus heights.

[0127] Based on the principle of detection, detection is performed through the collected spectrum of the surface of the object to be tested. Therefore, using the spectrum fitting parameter value to obtain the first in-focus height is conducive to improving the credibility of the data and thus improving the focusing accuracy.

[0128] In this embodiment, since the spectrum is obtained by collecting the reflectance of the surface of the object to be measured, the test spectrum includes a curve of preset parameters and wavelength, and the preset parameters are related to the reflectance. Specifically, the preset parameters include phase, amplitude, phase sine, or phase negative sine. The phase sine and phase negative sine are trigonometric functions of the phase, which have the effect of normalizing the data during data fitting, making it easier to calculate the spectrum fitting parameter values.

[0129] It should be noted that, during the focusing process, appropriate types of preset parameters can be selected for fitting according to actual needs (for example, according to the different products to be tested), so as to achieve fast convergence and high accuracy.

[0130] It should also be noted that the object to be tested is placed at the spectrum acquisition reference position, that is, the reference focusing height position. Therefore, during the first acquisition of the test spectrum, the object to be tested and the optical device are relatively moved from the spectrum acquisition reference position along the focusing direction to the initial focusing height position.

[0131] In addition, the focusing height is the distance between the object to be tested and the objective lens of the optical device. Therefore, in the process of collecting test spectra of the object to be tested at different test focusing heights, changing the focusing position is equivalent to changing the distance between the object to be tested and the objective lens of the optical device. Therefore, the position of the spectrum collector 50 can be fixed and the object to be tested can be moved along the focusing direction to make the object to be tested and the optical device move relative to each other to positions with different test focusing heights; or, the position of the object to be tested can be fixed and the spectrum collector 50 can be moved along the focusing direction to make the object to be tested and the optical device move relative to each other to positions with different test focusing heights.

[0132] That is, while the position of the spectrum collector is fixed, the focus height can be adjusted by moving the object under test along the focus direction via the focus height adjustment module 40. Similarly, while the position of the object under test is fixed, the focus height can be adjusted by moving the spectrum collector along the focus direction via the focus height adjustment module 40. By fixing the position of the spectrum collector or the object under test, changing the focus position is simplified. In other embodiments, during each step of collecting a test spectrum, the spectrum collector and the object under test can be moved simultaneously to change the focus position.

[0133] The spectrum fitting parameter values obtained by the calculation module 60 are used to determine whether the object under test is in focus, thereby adjusting the focus of the object under test. In this embodiment, depending on the calculation method (i.e., algorithm) of the spectrum fitting parameter values, the spectrum fitting parameter values can be positively correlated with the error values between the test spectrum and the reference spectrum, or negatively correlated with the error values between the test spectrum and the reference spectrum.

[0134] In this embodiment, the calculation module 60 includes: a first calculation unit (not shown in the figure), which is used to calculate the error value between each test spectrum and the reference spectrum; and a second calculation unit (not shown in the figure), which is used to obtain the spectrum fitting parameter value corresponding to the test focus height based on the error value.

[0135] In this embodiment, the spectrum fitting parameter value is negatively correlated with the error value. As an example, the relationship between the spectrum fitting parameter value and the error value is GOF=exp(-rmse), or GOF=rmse-1 , where GOF is the spectral fitting parameter value, and rmse is the error value. Therefore, a larger spectral fitting parameter value indicates a smaller error between the test spectrum and the reference spectrum, and the closer the test spectrum is to the reference spectrum, the better the focus. Conversely, a smaller spectral fitting parameter value indicates a worse focus.

[0136] In other embodiments, the spectral fitting parameter value is positively correlated with the error value, and the relationship between the spectral fitting parameter value and the error value is GOF = exp(rmse), or GOF = rmse, where GOF is the spectral fitting parameter value and rmse is the error value. Accordingly, when the spectral fitting parameter value and the error value are positively correlated, a larger GOF value indicates a worse focus condition, and vice versa, a smaller GOF value indicates a better focus condition.

[0137] In this embodiment, the relationship of the error value includes:

[0138] or

[0139] Wherein, rmse is the error value, ΔI is the square or absolute value of the difference between the preset parameter values of the test spectrum and the reference spectrum, and λ is the wavelength of the test spectrum and the reference spectrum.

[0140] It should be noted that a suitable type of relationship can be selected to calculate the error value according to actual needs (for example, according to different products to be tested).

[0141] It should also be noted that, as an example, the spectrum collector 50 and the calculation module 60 may operate alternately. That is, after each test spectrum is collected, the spectrum fitting parameter values for the test spectrum corresponding to the test focus height and the reference spectrum are obtained. In other embodiments, after the spectrum collector is used to collect test spectra of the object under test at various test focus heights, the calculation module may then be used to obtain the spectrum fitting parameter values for each test spectrum corresponding to each test focus height and the reference spectrum.

[0142] It can be seen from the above records that the spectral fitting parameter value can characterize the quality of the focusing condition. Therefore, the test focusing height corresponding to the spectral fitting parameter value that minimizes the error value is extracted through the data processing module 70, thereby obtaining the test focusing height with the best focusing condition, which is the first focusing height.

[0143] Accordingly, during subsequent actual testing of the object under test, the object under test and the optical device are relatively moved to the first in-focus height. Since the spectrum fitting parameter value at the first in-focus height is relatively high, this is conducive to improving the detection accuracy of the object under test. For example, the reliability of the film thickness obtained by the test is higher.

[0144] In this embodiment, the spectrum fitting parameter value is negatively correlated with the error value. Therefore, the data processing module 70 obtains the test focus height corresponding to the maximum spectrum fitting parameter value as the first in-focus height. When the spectrum fitting parameter value is negatively correlated with the error value, a larger spectrum fitting parameter value indicates a smaller error between the test spectrum and the reference spectrum, and a closer the test spectrum is to the reference spectrum, correspondingly indicating a better in-focus condition. Conversely, a smaller spectrum fitting parameter value indicates a worse in-focus condition. Therefore, the data processing module 70 obtains the test focus height corresponding to the maximum spectrum fitting parameter value as the first in-focus height.

[0145] In other embodiments, when the spectral fitting parameter value is positively correlated with the error value, a larger spectral fitting parameter value indicates a worse in-focus condition, and vice versa. Therefore, the data processing module obtains the test focusing height corresponding to the minimum spectral fitting parameter value as the first in-focus height.

[0146] It should be noted that the optical device further includes a detection module 90. The detection module is used to detect the object to be detected.

[0147] In this embodiment, the detection module has a second in-focus height, and there is a preset distance between the second in-focus height and the first in-focus height, and the preset distance is zero or non-zero.

[0148] It should be noted that, through pre-design, the difference in in-focus height between the detection module and the spectrum collector is typically known. Therefore, once the first in-focus height of the spectrum collector is obtained, the second in-focus height of the detection module can be obtained. Specifically, the preset distance is zero or non-zero, that is, the first in-focus height and the second in-focus height can be equal or unequal.

[0149] Therefore, the focus height adjustment module 40 is further used to relatively move the object to be measured and the detection module to the position of the second focus height, and to keep the object to be measured and the detection module at the position of the second focus height.

[0150] By relatively moving the object to be tested and the detection module to the second in-focus height, and maintaining them at the second in-focus height, preparations are made for subsequent actual testing of the object to be tested. For example, when measuring the film thickness of an object to be tested, it is necessary to measure different positions of the object to be tested. By maintaining the object to be tested and the detection module at the second in-focus height, measurements can be performed at different positions of the object to be tested based on the second in-focus height, thereby increasing the reliability of the film thickness data obtained.

[0151] The detection module 90 is configured to detect the object to be detected after the object to be detected and the optical device are kept at the second in-focus height.

[0152] According to the detection requirements, the object to be tested is tested to achieve defect detection, film thickness detection or line width (CD) detection of the object to be tested.

[0153] In this embodiment, description is made by taking the example that the first in-focus height and the second in-focus height are equal.

[0154] As an example, the geometric dimensions of the object under test are obtained based on the test spectrum corresponding to the first in-focus height. As an example, the object under test is a film layer under test, and therefore, the geometric dimensions include the thickness or width of the film layer under test. In other embodiments, depending on the type of the object under test, other types of geometric dimensions can also be detected. In other embodiments, the detection module is not limited to detection based on the test spectrum and can also use other detection methods for detection.

[0155] An embodiment of the present invention further provides a device, which can implement the focusing method of the optical device provided by the embodiment of the present invention by loading the focusing method of the optical device in the form of a program.

[0156] refer to Figure 5 , which shows a hardware structure diagram of a device provided by an embodiment of the present invention. The device of this embodiment includes: at least one processor 01, at least one communication interface 02, at least one memory 03 and at least one communication bus 04.

[0157] In this embodiment, the number of the processor 01 , the communication interface 02 , the memory 03 and the communication bus 04 is at least one, and the processor 01 , the communication interface 02 and the memory 03 communicate with each other through the communication bus 04 .

[0158] The communication interface 02 may be an interface of a communication module for network communication, such as an interface of a GSM module.

[0159] The processor 01 may be a central processing unit (CPU), or an application-specific integrated circuit (ASIC), or one or more integrated circuits configured to implement the focusing method described in this embodiment.

[0160] The memory 03 may include a high-speed RAM memory, and may also include a non-volatile memory (non-volatile memory), such as at least one disk memory.

[0161] The memory 03 stores one or more computer instructions, and the one or more computer instructions are executed by the processor 01 to implement the focusing method of the optical device provided in the above embodiment.

[0162] It should be noted that the above-mentioned terminal device may also include other devices (not shown) that may not be necessary for understanding the contents disclosed in the embodiments of the present invention; given that these other devices may not be necessary for understanding the contents disclosed in the embodiments of the present invention, the embodiments of the present invention will not introduce them one by one.

[0163] An embodiment of the present invention further provides a storage medium storing one or more computer instructions, wherein the one or more computer instructions are used to implement the focusing method of the optical device provided in the above embodiment.

[0164] In the focusing method of an embodiment of the present invention, by obtaining a reference spectrum and a test spectrum of the object to be tested at different test focusing heights, and obtaining spectral fitting parameter values corresponding one-to-one to the test focusing heights, the test focusing height corresponding to the spectral fitting parameter value that minimizes the error value is extracted as the first in-focus height. The embodiment of the present invention directly uses the fitting parameter (Goodness of Fit, GOF) value of the spectral data to determine whether the object to be tested is in focus, thereby adjusting the focus of the object to be tested. Therefore, the embodiment of the present invention can improve the focusing efficiency while ensuring the focusing accuracy without adding additional hardware modules (for example, a focusing detection module).

[0165] The embodiments of the present invention described above are combinations of elements and features of the present invention. Unless otherwise mentioned, the elements or features may be considered as optional. Each element or feature may be put into practice without being combined with other elements or features. In addition, the embodiments of the present invention may be constructed by combining some elements and / or features. The order of operations described in the embodiments of the present invention may be rearranged. Some configurations of any one embodiment may be included in another embodiment and may be replaced by the corresponding configuration of another embodiment. It is obvious to those skilled in the art that claims that do not have a clear reference relationship to each other in the appended claims may be combined into embodiments of the present invention, or may be included as new claims in amendments after submitting this application.

[0166] The embodiments of the present invention may be implemented by various means such as hardware, firmware, software, or a combination thereof. In a hardware configuration, the method according to the exemplary embodiment of the present invention may be implemented by one or more application specific integrated circuits (ASICs), digital signal processors (DSPs), digital signal processing devices (DSPDs), programmable logic devices (PLDs), field programmable gate arrays (FPGAs), processors, controllers, microcontrollers, microprocessors, etc.

[0167] In a firmware or software configuration, the embodiments of the present invention may be implemented in the form of modules, procedures, functions, and the like. Software codes may be stored in a memory unit and executed by a processor. The memory unit may be located inside or outside the processor and may send and receive data to and from the processor via various known means.

[0168] The above description of the disclosed embodiments will enable one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention is not limited to the embodiments shown herein, but is to be construed in the widest possible manner consistent with the principles and novel features disclosed herein.

[0169] Although the present invention is disclosed as above, the present invention is not limited thereto. Any person skilled in the art can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the scope of protection of the present invention should be based on the scope defined by the claims.

Claims

1. A focusing method for an optical device, characterized in that: The optical device includes a spectrum collector, and the focusing method includes: Obtain a reference spectrum; Collecting the test spectrum of the object to be tested at different test focus heights by the spectrum collector; Obtaining spectrum fitting parameter values of each of the test spectrum and the reference spectrum, wherein the spectrum fitting parameter values are positively correlated or negatively correlated with the error value between the test spectrum and the reference spectrum; Extracting, according to the spectrum fitting parameter value, a test focus height corresponding to the spectrum fitting parameter value that minimizes the error value as a first in-focus height; The step of obtaining the reference spectrum includes: providing a theoretical model of interaction between the sample and light, wherein the theoretical model is used to represent the relationship between the spectrum of the emitted light after the light interacts with the sample and the physical parameters of the sample; Using the physical parameters of the object to be measured as the physical parameters of the sample, obtaining an output light spectrum according to the theoretical model to serve as the reference spectrum; The focusing method further includes: obtaining the geometric dimensions of the object to be measured according to a test spectrum corresponding to the first in-focus height; Wherein, the object to be measured is a film layer to be measured, and the geometric dimensions include the thickness or line width of the film layer to be measured.

2. The focusing method according to claim 1, wherein: Before collecting the test spectra of the object to be tested at different test focus heights by the spectrum collector, the focusing method further includes: determining a focus height range and a preset moving step, the focus height range having a minimum focus height and a maximum focus height, and any focus height between the minimum focus height and the maximum focus height being used as an initial focus height; The step of collecting the test spectra of the object to be tested at different test focusing heights by the spectrum collector includes: starting from the initial focusing height position, changing the focusing position according to the preset moving step within the focusing height range, so that the object to be tested and the optical device are relatively moved to positions at different test focusing heights, and collecting the test spectra of the object to be tested at different test focusing heights.

3. The focusing method according to claim 1, wherein: The test spectrum includes a curve of preset parameters and wavelength, and the preset parameters are related to reflectivity.

4. The focusing method according to claim 1, wherein: The step of obtaining the spectral fitting parameter value includes: calculating the error value between each test spectrum and the reference spectrum; obtaining the spectral fitting parameter value corresponding to the test focus height according to the error value, wherein the spectral fitting parameter value is negatively correlated with the error value, and the relationship between the spectral fitting parameter value and the error value is GOF=exp(-rmse), or GOF=rmse -1 , where GOF is the spectrum fitting parameter value, and rmse is the error value; The step of extracting the test focus height corresponding to the spectrum fitting parameter value that minimizes the error value as the first in-focus height according to the spectrum fitting parameter value includes: obtaining the test focus height corresponding to the maximum spectrum fitting parameter value as the first in-focus height.

5. The focusing method according to claim 1, wherein: The step of obtaining the spectral fitting parameter value includes: calculating the error value between each of the test spectra and the reference spectrum; obtaining the spectral fitting parameter value corresponding to the test focus height according to the error value, wherein the spectral fitting parameter value is positively correlated with the error value, and the relationship between the spectral fitting parameter value and the error value is GOF=exp(rmse), or GOF=rmse, wherein GOF is the spectral fitting parameter value and rmse is the error value; The step of extracting, according to the spectrum fitting parameter value, the test focus height corresponding to the spectrum fitting parameter value that minimizes the error value as the first in-focus height includes: obtaining the test focus height corresponding to the minimum spectrum fitting parameter value as the first in-focus height.

6. The focusing method according to claim 3, wherein: In the step of obtaining the spectrum fitting parameter values of each of the test spectra and the reference spectrum, the relationship formula of the error value includes: or Wherein, rmse is the error value, ΔI is the square or absolute value of the difference between the preset parameter values of the test spectrum and the reference spectrum, and λ is the wavelength of the test spectrum and the reference spectrum.

7. The focusing method according to claim 3 or 6, characterized in that: The preset parameters include phase, amplitude, phase sine or phase negative sine.

8. The focusing method according to claim 2, wherein: Before determining the focusing height range, the focusing method further includes: determining a spectrum collection reference position, wherein the spectrum collection reference position has a reference focusing height; A focusing height range is determined according to the reference focusing height, and the reference focusing height is within the focusing height range.

9. The focusing method according to claim 8, wherein: Before collecting the test spectrum of the object to be tested at different test focusing heights by the spectrum collector, the focusing method further comprises: placing a product substrate, on which the object to be tested is formed; Before placing the product substrate, the spectrum collection reference position is determined, and the step of determining the spectrum collection reference position includes: placing a reference substrate, which is the same as the product substrate; and obtaining the in-focus height of the reference substrate as the spectrum collection reference position.

10. The focusing method according to claim 8, wherein: Before collecting the test spectra of the object to be tested at different test focusing heights by the spectrum collector, the focusing method further comprises: placing the object to be tested and placing the object to be tested at the spectrum collection reference position; The step of collecting the test spectrum for the first time includes: moving the object to be tested and the optical device relatively to the initial focus height position along the focus direction from the spectrum collection reference position.

11. The focusing method according to claim 8, wherein: The difference between the minimum focusing height and the reference focusing height is -0.05 mm to -0.1 mm, and the difference between the maximum focusing height and the reference focusing height is 0.05 mm to 0.1 mm.

12. The focusing method according to claim 2, wherein: The preset moving step length is 0.5 microns to 20 microns.

13. The focusing method according to claim 1, wherein: The optical device further includes a detection module, the detection module having a second in-focus height, a preset distance between the second in-focus height and the first in-focus height, and the preset distance is zero or non-zero; The focusing method further comprises: relatively moving the object to be measured and the detection module to a position at a second in-focus height, and maintaining the object to be measured and the detection module at the position at the second in-focus height; After the object to be tested and the detection module are kept at the second in-focus height, the object to be tested is detected by the detection module.

14. The focusing method according to claim 1, wherein: The step of collecting the test spectra of the object to be tested at different test focus heights by the spectrum collector includes: fixing the position of the spectrum collector and moving the object to be tested along the focus direction so as to relatively move the object to be tested and the optical device to positions at different test focus heights; Alternatively, the position of the object to be tested is fixed, and the spectrum collector is moved along the focusing direction to enable the object to be tested and the optical device to move relative to positions at different test focusing heights.

15. The focusing method according to claim 1, wherein: The spectrum collector includes an ellipsometer, a reflection spectrometer or a spectroscopic scatterometer.

16. A focusing system for an optical device, characterized in that: include: A reference spectrum acquisition module, used for acquiring a reference spectrum; A spectrum collector is used to collect the test spectrum of the object under test at different test focus heights; a calculation module, configured to obtain a spectrum fitting parameter value of each of the test spectra and the reference spectrum, wherein the spectrum fitting parameter value is positively correlated or negatively correlated with an error value between the test spectrum and the reference spectrum; a data processing module, configured to extract, based on the spectrum fitting parameter value, a test focus height corresponding to the spectrum fitting parameter value that minimizes the error value, as a first in-focus height; The reference spectrum acquisition module includes: a model providing unit, configured to provide a theoretical model of the interaction between the sample and light, wherein the theoretical model is configured to represent the relationship between the spectrum of the emitted light after the light interacts with the sample and the physical parameters of the sample; a spectrum output unit, configured to use the physical parameters of the object to be measured as the physical parameters of the sample, and to obtain the spectrum of the emitted light according to the theoretical model, for use as the reference spectrum; The data processing module is further used to: Obtaining the geometric dimensions of the object to be measured according to the test spectrum corresponding to the first in-focus height; Wherein, the object to be measured is a film layer to be measured, and the geometric dimensions include the thickness or line width of the film layer to be measured.

17. A device, characterized in that The invention comprises at least one memory and at least one processor, wherein the memory stores one or more computer instructions, wherein the one or more computer instructions are executed by the processor to implement the focusing method according to any one of claims 1 to 15.

18. A storage medium, characterized in that The storage medium stores one or more computer instructions, and the one or more computer instructions are used to implement the focusing method according to any one of claims 1 to 15.

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