CN117075431A - Measuring method for focal plane of exposure lens - Google Patents

Abstract

A method for measuring the focal surface of the exposure lens of a direct-write lithography machine. The test focal surface value group Z _n and the test pattern are determined according to the basic focal surface value Z ₀ of the exposure lens of the direct-write lithography machine. The test pattern includes multiple The unit test patterns are arranged in rows and columns. The test focal surface value group includes multiple test focal surface values with different values. Each unit test pattern corresponds to a test focal surface value; the reference focal surface of the direct writing lithography machine is set as the test focal surface respectively. , respectively, expose the corresponding unit test pattern on the test workpiece; after completing the development, obtain the image of the unit test pattern through the image acquisition device, and obtain the amplitude of the unit test image in the diffraction domain by performing data processing on the obtained unit test image, and obtain Test the focal surface value and the amplitude fitting function curve in the diffraction domain to obtain the true focal surface of the exposure lens with high measurement accuracy.

Description

A method of measuring the focal plane of an exposure lens

Technical field

The present invention relates to the technical field of laser direct writing, in particular to a method for measuring the focal plane of an exposure lens of a laser direct writing device.

Background technique

The existing method of measuring the actual focal plane of a lithography machine is to use a fixed exposure lens to move the workbench loading the workpiece in the vertical direction. By moving the workbench, the workpiece is exposed at different heights for line graphics, and the exposure is completed. After development, use a microscope or CD-SEM (scanning electron microscope) to observe the imaging quality or detect the key dimensions of the exposure lines to determine the actual focal plane position of the lithography machine. The measurement method of measuring critical dimensions requires the use of external equipment (such as a microscope, etc.). Manual measurement errors are large, traceability is low, and errors introduced by workpiece warpage cannot be avoided, and cannot meet the requirements of high-precision equipment.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for measuring the focal plane of an exposure lens of high-precision equipment.

In order to solve the above problems, the present invention provides a method for measuring the focal surface of the exposure lens of a direct-write lithography machine. The test focal surface value group Z _n and the test pattern are determined according to the basic focal surface value Z ₀ of the exposure lens of the direct-write lithography machine. , the test pattern includes a plurality of unit test patterns arranged in rows and columns, the test focal surface value group includes a plurality of test focal surface values with different values, each unit test pattern corresponds to a test focal surface value; respectively, the direct writing lithography machine The reference focal plane is set as the test focal plane, and the corresponding unit test patterns are exposed on the test workpiece according to the positional relationship of the test patterns. After the exposure is completed, the test workpiece is developed. After the development is completed, the unit test pattern is obtained through the image acquisition device. Image, the image of the unit test pattern corresponding to a test pattern constitutes a set of image data sets. By performing data processing on the acquired unit test image, the amplitude of the unit test image in the diffraction domain is obtained. By performing unit tests on the image data set The test focal plane value corresponding to the image and the amplitude in the diffraction domain are fitted to the function curve to obtain the true focal plane of the exposure lens.

Further, the unit test patterns are arranged in N rows and N columns, and N is an odd number not less than 3.

Further, the unit test pattern corresponding to the basic focal plane value Z ₀ as the test focal plane is located at the center of the test pattern as the central test pattern, and the unit test patterns corresponding to the other test focal plane values are arranged around the central test pattern.

Furthermore, design the position of the unit test pattern corresponding to the test focus area value to avoid that the test focus area values corresponding to each row of unit test patterns are arranged from small to large, or from large to small; at the same time, avoid the test corresponding to each column of unit test pattern The focal area values are arranged from small to large, or from large to small.

Further, the test focal surface value group Z _n is obtained based on the basic focal surface value Z ₀ , and floats symmetrically up and down with the basic focal surface value Z ₀ as the intermediate value. The test focal surface values in the test focal surface value group are arranged from small to large or from large to small. When , the difference between adjacent test focal plane values is the same unit focal plane value U ₀ .

Furthermore, the test focal surface value corresponding to the unit test image and the amplitude fitting function curve in the diffraction domain are quadratic function curves, and the focal surface value corresponding to the vertex of the function curve is the true focal surface of the exposure lens at this time.

Further, the quadratic function curve is obtained by using Gaussian filtering to remove values with large deviations, and then performing least squares data fitting.

Further, when the test workpiece is exposed to the corresponding unit test pattern, the exposure dose used is greater than the optimal exposure dose of the test workpiece.

Further, the test workpiece has an alignment point. Select a test workpiece with an alignment point or expose the alignment point on the test workpiece before exposing the test pattern.

Further, the unit test pattern is a pattern arranged in an array.

A method for measuring the focal plane control accuracy of an exposure lens of a direct-write lithography machine with a focusing device. Before exposing the test pattern, the surface shape data of the test workpiece is first obtained through the height detection unit. The automatic focusing device is based on the height. Use the data to adjust the focal plane of the exposure lens to adapt to different heights of the test workpiece; use the above measurement method for the focal plane of the exposure lens to measure the real focal plane of the exposure lens with a focusing device at the exposure test pattern of the test workpiece. According to the obtained real focal plane of the exposure lens Focal plane, calculate the moving distance of the automatic focusing device, and compare and analyze it with the height data of the test workpiece at the corresponding position to obtain the control accuracy of the automatic focusing device.

Compared with the existing technology, by setting different test focal plane exposure unit test patterns, the test unit patterns are arranged in an array, and the amplitude of the test pattern composed of the unit test patterns and the function curve of the test focal plane are obtained to obtain the true focal plane value, and the measurement accuracy is High, at the same time, through the test pattern, the test focal plane values corresponding to the unit test patterns in the row direction and/or the unit test patterns in the column direction have different numerical rising directions and numerical falling directions, avoiding the formation of tilts in the row direction and/or column direction. The focal plane introduces first-order errors.

Description of the drawings

Figure 1 is a schematic diagram of a direct-write lithography machine.

Figure 2 is a schematic block diagram of a method for measuring the true focal plane of the exposure lens of a direct-write lithography machine.

FIG. 3 is a schematic diagram of a test focal plane corresponding to a test pattern according to an embodiment.

FIG. 4 is a schematic diagram of a test pattern according to an embodiment.

Figure 5 is a schematic diagram of the completion of exposure of the test workpiece with alignment points.

Figure 6 is a schematic diagram of the function curve of amplitude and test focal plane.

FIG. 7 is a schematic diagram of a test focal plane corresponding to a test pattern in another embodiment.

Detailed ways

In order to make the purpose, technical solutions and advantages of the present invention clearer, the present invention is described below through the specific embodiments shown in the drawings.

As shown in Figure 1, an example of a direct-write lithography machine is shown. The direct-write lithography machine includes a base 1, a gantry mechanism 2, an exposure mechanism 3, an alignment mechanism 4, and a multi-axis motion platform ( 5, 6, 7), substrate platform 8 and control system. The control system controls the exposure mechanism 3, the alignment mechanism 4, the multi-axis motion platform (5, 6, 7) and the substrate platform 8. The base 1 is provided with the gantry mechanism 2 and a multi-axis movement platform (5, 6, 7). The multi-axis movement platform (5, 6, 7) is provided with the substrate platform 8. The gantry The alignment mechanism 4 and the exposure mechanism 3 are provided on the mechanism. The multi-axis motion platform (5, 6, 7) drives the substrate platform to move in the X direction, Y direction and Z direction, and the alignment system 4 and the exposure system 3 can be fixedly arranged with the gantry mechanism 2, It can also be slidably installed on the gantry mechanism 2 .

The exposure mechanism 3 includes a plurality of exposure lenses 30, and the alignment mechanism 4 includes at least one image acquisition device 40. The image acquisition device 40 is fixedly or slidingly arranged.

The multi-axis motion platform (5, 6, 7) includes a y-axis motion component 6, an x-axis motion component 5 and a z-axis motion component 7. The y-axis motion component 6 is fixed on the marble base. 1, the x-axis motion component 5 is fixed on the y-axis motion component 6, and the z-axis motion component 7 is fixed on the x-axis motion component 5. The x-axis movement component 5 drives the substrate platform 8 to move along the X direction, the y-axis movement component 6 drives the substrate platform 8 to move along the Y direction, and the z-axis movement component 7 drives the substrate platform 8 along the Y direction. Z-axis vertical movement.

It should be understood that the above is only an illustrative description of the configuration of a conventional direct-write lithography machine in this field. In practical applications, its configuration may exist in various forms. For example, the motion platform and the substrate platform may only be There can be one or two multi-axis motion platforms. The x-axis motion component and/or the z-axis motion component can be reduced as needed. The exposure lens can be fixedly installed or moved. Other conventional deformations will not be listed one by one.

As shown in Figure 2, the following is a detailed description of the measurement method of the true focal plane of the exposure lens of a direct-write lithography machine.

The test focal surface value group Z _n and the test pattern are determined according to the basic focal surface value Z ₀ of the exposure lens of the direct-write lithography machine. The basic focal plane value Z ₀ is the preliminary measured coarse focal plane value. By moving the camera in the Z direction, the static projection image of the exposure lens can be captured at different Z direction heights, and the camera Z direction height and image grayscale value can be fitted. , the height in the Z direction corresponding to its extreme point is the coarse focal plane value of the exposure lens; or by adjusting the height of the test workpiece in the Z direction, the exposure lens exposes lines to the test workpiece respectively when the test workpiece is at different heights. The height corresponding to the Z direction when the critical dimension (CD value) of the line is closest to the theoretical value is the coarse focal plane. The test focal surface value group Z _n is obtained based on the basic focal surface value Z ₀ , and floats symmetrically up and down with the basic focal surface value Z ₀ as the middle value. When the test focal surface values in the test focal surface value group are arranged from small to large or from large to small, adjacent tests The difference between the focal plane values is the same unit focal plane value U ₀ . The test pattern includes a plurality of unit test patterns. The unit test pattern is arranged in N rows and N columns. The N is an odd number not less than 3. The N value can be selected according to the theoretical focal depth and step of the exposure lens. The step value S ₀ is determined, (N*N-1)* S ₀ ≥ lens focal depth, and the step value refers to the unit relative movement distance between the lens and the workpiece. Each unit test pattern corresponds to a test focal surface value. With the basic focal surface value Z ₀ as the test focal surface, the unit test pattern corresponding to the test focal surface is located in the center of the test pattern as the central test pattern. The unit test patterns corresponding to the other test focal surface values are tested around the center. Pattern settings. It is better to design the position of the unit test pattern corresponding to the test focus area value to avoid that the test focus area value corresponding to the unit test pattern in each row is arranged from small to large, or from large to small; at the same time, avoid that the unit test pattern corresponding to each column of the unit test pattern is arranged The test focus area values are arranged from small to large, or from large to small. Preferably, the unit test pattern is a pattern arranged in an array. Preferably, the graphics are regular graphics such as circles and squares. The pattern is preferably the smallest size that can ensure a complete pattern after exposure and development. .

The unit test patterns are sequentially exposed on the test workpiece according to the test focal plane corresponding to the unit test pattern in the test pattern. There are gaps between adjacent unit test patterns to facilitate distinguishing unit test pattern boundaries. Preferably, before exposing the unit test pattern, an alignment point is exposed on the test workpiece to align the unit test pattern, so as to facilitate quick positioning of the unit test pattern in the later stage. When the test workpiece is exposed to the corresponding unit test pattern, the exposure dose used is greater than the optimal exposure dose of the test workpiece. The optimal exposure dose is the exposure lens of the lithography machine when supported by dry film or photoresist. The ultimate exposure dose corresponding to the complete realization of the ultimate resolution size.

Develop the exposed test workpiece. The development process is more conducive to observing small changes in image characteristics. Especially for high-precision machines with small lens focal depth, it can avoid the situation where the image distinction is not obvious. Place the workpiece on the direct-write lithography machine again, and obtain the developed unit test pattern through the image acquisition module of the direct-write lithography machine to obtain an image data set. The image data set includes all unit test images corresponding to different locations and different test focal planes. Preferably, based on the alignment point of the test workpiece, the position of the unit test pattern is accurately obtained, and the unit test pattern is obtained more quickly. You can directly select the test workpiece with alignment points or expose the alignment points on the test workpiece before exposing the test pattern.

Based on the collected image data set, image data processing is performed. All the unit test image data in a test image is a set of analysis data. The amplitude of the unit test image in the diffraction domain is obtained. The relationship between the test focal surface value of the unit test image and the amplitude in the diffraction domain is obtained. The function curve is fitted by The obtained function curve finds the true focal plane of the exposed lens. When fitting the function curve, the amplitude of the unit test image in the diffraction domain is used as the ordinate, and the test focal plane value corresponding to the unit test image is used as the abscissa. Preferably, before extracting the amplitude in the diffraction domain, first perform full-frame denoising to filter out noise to ensure that each unit test image only includes clear and complete unit test images. If the obtained unit test image is "255 ” or “0” saturation state, you need to adjust the light source brightness of the image acquisition device and acquire it again. Preferably, Gaussian filtering is first used to remove values with large deviations, and then least squares data fitting is performed to obtain a quadratic function curve of amplitude and test focal plane. The focal plane value corresponding to the vertex of the function curve is directly written at this time. The real focal plane of the lithography machine. The amplitude of the unit test image in the diffraction domain is obtained by Fourier transform of the gray value of the unit test image extracted by the image processing software. Preferably, before extracting the gray value of the unit test image, the obtained unit test image is first denoised to avoid interference.

The real focal surface of the exposure lens of the direct-write lithography machine can be obtained by exposing one test pattern, or by exposing multiple test patterns, obtaining multiple test data, and obtaining the average value of multiple test data. Get the true focal plane.

By setting different test focal plane exposure unit test patterns, the test unit patterns are arranged in an array, and the amplitude of the test pattern composed of the unit test pattern and the function curve of the test focal plane are obtained to obtain the true focal plane value. The measurement accuracy is high. At the same time, the test is passed. The test focal plane values corresponding to the unit test patterns in the row direction and/or the unit test patterns in the column direction in the pattern have different numerical ascending directions and numerical descending directions to avoid first-order errors caused by the formation of tilted focal planes in the row direction and/or column direction.

Next, as shown in Figures 3 to 7, the test pattern includes 9 unit test patterns 10 arranged in three rows and three columns as an example. The 9 unit test patterns correspond to 9 test focal surface values, respectively Z ₁ , Z ₂ , Z ₃ , Z ₄ , Z ₅ , Z ₆ , Z ₇ , Z ₈ , Z ₉ .

The test focal surface values Z ₁ to Z ₉ are arranged from small to large, and the middle value Z ₅ in the test focal surface value group is equal to the basic focal surface value Z ₀ .

Z ₄ and Z ₆ adjacent to Z ₅ are respectively different from Z ₅ by twice the unit focal surface value U ₀ , Z ₄ =Z ₀ -U ₀ , Z ₆ =Z ₀ +U ₀ .

Z ₃ and Z ₇ are respectively different from Z ₅ by twice the unit focal surface value U ₀ , Z ₃ =Z ₀ -2U ₀ , Z ₇ ==Z ₀ +2U ₀ .

Z ₂ and Z ₈ respectively differ from Z ₅ by three times the unit focal surface value U ₀ , Z ₂ =Z ₀ -3U ₀ , Z ₈ ==Z ₀ +3U ₀ .

Z ₁ and Z ₉ are respectively four times different from Z ₅ in unit focal surface value U ₀ , Z ₁ =Z ₀ -4U ₀ , Z ₉ ==Z ₀ +4U ₀ .

In the test pattern, the test focal surface value corresponding to the first unit test pattern located at the first position in the first row is Z ₉ , and the test focal surface value corresponding to the second unit test pattern located at the second position in the first row is Z ₆ . The test focal surface value corresponding to the third unit test pattern located in the third position in a row is Z ₃ , the test focal surface value corresponding to the fourth unit test pattern located in the first position in the second row is Z ₂ , and the test focal surface value corresponding to the test pattern located in the second position in the second row is Z 2 The test focal surface value corresponding to the fifth unit test pattern is Z ₅ , the test focal surface value corresponding to the sixth unit test pattern located at the third position in the second row is Z ₈ , and the seventh unit test pattern located at the first position in the third row corresponds to The test focal surface value of is Z ₇ , the test focal surface value corresponding to the eighth unit test pattern located in the second position of the third row is Z ₄ , and the corresponding test focal surface value of the ninth unit test pattern located in the third position of the third row is Z ₁ . The test focal plane value corresponding to the unit test pattern located at the center of the test pattern is Z ₅ . In this embodiment, with the test focal plane value Z ₅ as the center, the two opposite test focal plane values of the center line and the diagonal line are relative to The test focal plane values Z ₅ differ by the same value. Those skilled in the art should know that the above embodiments are only exemplary. The setting of the test focal surface value corresponding to the unit test pattern must satisfy the requirement of at least one unit test pattern located in the middle position among the test focal surface values corresponding to the unit test patterns in one row or each column. The corresponding test focus area value is the maximum or minimum value; for the case where the test focus area values corresponding to each row or column of unit test patterns are arranged in order from small to large or from large to small, at least one row or column of unit test patterns corresponds to the maximum value or the minimum value. The arrangement direction of the corresponding test focal surface values is different from that of the other rows. For example, in the embodiment, it includes three rows of unit test patterns. The test focal surface values corresponding to one row of unit test patterns are arranged from small to large from left to right, and the other two rows are The test focus area values corresponding to the unit test patterns are arranged from large to small from left to right; similarly, the test focus area values corresponding to one column of unit test patterns are arranged from small to large from top to bottom, and the units in the other two columns are arranged from small to large. The test focal plane values corresponding to the test patterns are arranged from large to small from top to bottom to avoid first-order errors caused by the formation of tilted focal planes in the row direction and/or column direction.

Set the reference focal plane value of the direct-write lithography machine to Z ₉ , adjust the motion platform in the vertical direction so that the test workpiece is at the reference focal plane, and expose the first unit test pattern on the test workpiece. Set the reference focal plane of the direct-write lithography machine to Z ₂ , adjust the movement platform in the vertical direction so that the test workpiece is at the reference focal plane, and adjust the position of the workpiece horizontally. According to the positional relationship of the test pattern, expose the third Four unit test pattern. Set the reference focal plane of the direct-write lithography machine to Z ₇ , adjust the movement platform in the vertical direction so that the test workpiece is at the reference focal plane, and adjust the position of the workpiece horizontally. According to the positional relationship of the test pattern, expose the third Seven unit test patterns. By analogy, according to the sequence shown in Figure 4, the exposure of the test image on the test workpiece is completed.

Perform a development operation on the exposed test workpiece, place the developed test workpiece on the motion platform of the direct-write lithography machine, obtain the test image through the image acquisition device, obtain the image data set of the unit test image, and perform image data processing . Use Gaussian filter to remove values with large deviations and perform least squares data fitting. As shown in Figure 6, a quadratic function curve of amplitude and test focal surface is obtained. The focal surface value corresponding to the vertex of the function curve is the direct writing formula at this time. The real focal plane of the lithography machine.

Before exposing the test pattern, you can also first expose the alignment point 20 on the test substrate, which is used to locate the position of the exposed test pattern, so that the test image can be quickly captured after the development is completed.

The above method of obtaining the true focal plane of a direct-write lithography machine can also be applied to a direct-write lithography machine with an automatic focusing device to measure the control accuracy of the focusing device. The automatic focusing device is used to adjust the focal plane of the exposure lens according to the height change of the workpiece.

Before exposing the test pattern, the surface shape data of the test workpiece is first obtained through the height detection unit. The automatic focusing device adjusts the focal plane of the exposure lens according to the surface shape data to adapt to different heights of the test workpiece.

When the test image is exposed to the test workpiece, the reference focal plane is set respectively. The automatic focusing device adjusts the focal plane according to the surface shape data of the test workpiece, completes the exposure of the unit test pattern corresponding to the reference focal plane, and completes the exposure of all unit test patterns. After exposure, develop the exposed workpiece, obtain the test image through the image acquisition device, conduct data analysis on the test image, and obtain the real focal plane at the corresponding position. According to the obtained real focal plane of the entire board of the test workpiece, and each real The position (X, Y) of the test workpiece corresponding to the focal plane fits the shape of the real focal plane of the test workpiece, and is compared with the surface shape data of the test workpiece obtained by the height detection unit to verify the compensation of the automatic focusing device. Is the focal plane value correct and the direction correct? Specifically, based on the obtained real focal plane, calculate the moving distance of the automatic focusing device, and compare and analyze it with the height data of the test workpiece at the corresponding position to compare whether the moving distance of the automatic focusing device changes with the height of the test workpiece (theoretical moving distance ) correspondingly, obtain the control accuracy of the autofocus device, and determine whether the control accuracy of the autofocus device is qualified. If the height change of the test workpiece and the moving distance of the automatic focusing device are within the error range, the control accuracy of the automatic focusing device meets the requirements. If the height change of the test workpiece and the moving distance of the automatic focusing device are beyond the error range, the automatic focusing device The control accuracy does not meet the requirements and needs to be corrected.

When measuring the control accuracy of the focusing device, multiple sets of exposure image data can be obtained, and the test focal plane is set as the reference focal plane. The automatic focusing device adjusts the focal plane according to the height data of the test workpiece, and adjusts the focal plane according to the positional relationship of the test pattern. Exposure of multiple unit test patterns corresponding to the reference focal plane is completed, exposure of all unit test patterns corresponding to one test focal plane is completed, and then exposure of multiple unit test patterns corresponding to the next test focal plane is performed. Until the exposure of the unit test patterns corresponding to all test focus areas is completed.

Claims (11)

1. A method for measuring the focal surface of the exposure lens of a direct-write lithography machine, which is characterized in that: the test focal surface value group Z _n and the test pattern are determined according to the basic focal surface value Z ₀ of the exposure lens of the direct-write lithography machine, so The above test pattern includes multiple unit test patterns arranged in rows and columns. The test focus value group includes multiple test focus values with different values. Each unit test pattern corresponds to a test focus value; respectively, the reference focus of the direct writing lithography machine is The surface is set as the test focal plane, and the corresponding unit test patterns are exposed on the test workpiece according to the positional relationship of the test patterns; after the exposure is completed, the test workpiece is developed. After the development is completed, the image of the unit test pattern is obtained through the image acquisition device. The images of the unit test pattern corresponding to a test pattern constitute a set of image data sets. By performing data processing on the acquired unit test images, the amplitude of the unit test image in the diffraction domain is obtained. By matching the unit test images in the image data set, The test focal surface value and the amplitude in the diffraction domain are fitted to the function curve to obtain the true focal surface of the exposure lens. 2. The method for measuring the focal plane of an exposure lens according to claim 1, wherein the unit test patterns are arranged in N rows and N columns, and N is an odd number not less than 3. 3. The measurement method of exposure lens focal plane according to claim 1, characterized in that: with the basic focal plane value Z ₀ as the test focal plane, the unit test pattern corresponding to the central position of the test pattern is the central test pattern, and the remaining tests The unit test pattern corresponding to the focal plane value is arranged around the central test pattern. 4. The method of measuring the focal surface of an exposure lens according to claim 3, characterized in that: the position of the unit test pattern corresponding to the test focal surface value is designed to avoid that the test focal surface values corresponding to each row of unit test patterns are arranged from small to large. , or arranged from large to small; at the same time, avoid that the test focus area values corresponding to each column of unit test patterns are arranged from small to large, or from large to small. 5. The method of measuring the focal surface of an exposure lens according to claim 1, characterized in that: the test focal surface value group _Zn is obtained according to the basic focal surface value _Z0 , and floats symmetrically up and down with the basic focal surface value _Z0 as the intermediate value, When the test focal surface values in the test focal surface value group are arranged from small to large or from large to small, the difference between adjacent test focal surface values is the same unit focal surface value U _{0 .} 6. The method of measuring the focal surface of an exposure lens according to claim 1, characterized in that: the test focal surface value corresponding to the unit test image and the amplitude fitting function curve in the diffraction domain are quadratic function curves, and the vertices of the function curve correspond to The focal plane value is the true focal plane of the exposed lens at this time. 7. The method of measuring the focal plane of an exposure lens according to claim 6, characterized in that: the quadratic function curve is obtained by performing least squares data fitting after removing values with large deviations using Gaussian filtering. 8. The method of measuring the focal plane of an exposure lens according to claim 1, characterized in that when the test workpiece is exposed to the corresponding unit test pattern, the exposure dose used is greater than the optimal exposure dose of the test workpiece. 9. The method for measuring the focal plane of an exposure lens according to claim 1, characterized in that: the test workpiece has an alignment point, and the test workpiece with the alignment point is selected or the test workpiece is exposed before exposing the test pattern. Counterpoint. 10. The method for measuring the focal plane of an exposure lens according to claim 1, wherein the unit test pattern is a pattern arranged in an array. 11. A method for measuring the focal plane control accuracy of an exposure lens of a direct-write lithography machine with a focusing device, characterized in that: before exposing the test pattern, the surface shape data of the test workpiece is first obtained through the height detection unit, and the automatic The focusing device adjusts the focal surface of the exposure lens according to the height data to adapt to different heights of the test workpiece; the exposure lens with the focusing device is measured at the exposure test pattern of the test workpiece using the measurement method of the focal surface of the exposure lens in any one of claims 1-11 According to the real focal plane of the exposure lens, the moving distance of the autofocus device is calculated, and compared and analyzed with the height data of the test workpiece at the corresponding position to obtain the control accuracy of the autofocus device.