Sub-aperture distribution planning method for large-warping plane interference measurement

Abstract

The invention discloses a sub-aperture distribution planning method for large warping plane interference measurement. The method is used in the in-situ sub-aperture splicing test process of a large warping plane by a phase shift interferometer, and the functions of automatically judging the warping characteristic of a tested piece, automatically calculating the number of sub-apertures and the compensation amount of each sub-aperture and the like are realized. According to the parameters obtained by the invention, the electric control objective table of the phase shift interferometer and measurement software can be directly driven to operate in a matched manner, so that the sequential measurement of different warped sub-aperture areas is completed. Therefore, the full-automatic interference test of a large warping plane as high as 100 microns is realized.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of optical measurement, in particular to a sub-aperture distribution planning method for large warping plane interferometry. BACKGROUND

[0002] The phase-shifting interferometer is a commonly used plane surface testing device, and the range thereof is between 20um and 30um, and generally, the large warping plane with a maximum warping degree reaching 100um cannot be directly measured. When the wafer as a representative of the large warping plane is measured by the phase-shifting interferometer, the problem that the interference image is cut and the whole plane cannot be measured often occurs in some regions. In the absence of a special device, the phase-shifting interferometer and the sub-aperture splicing technology are often used in the prior art to realize the detection of the large warping plane. The method only needs to adjust the tilt amount of the measured plane in the measurement process, sample the interference images of different warping regions in turn, save a plurality of sub-aperture data, splice all the sub-apertures after the sampling is completed, and finally realize the sampling covering the whole region of the measured wafer.

[0003] However, since the warping characteristics of each region of the measured piece cannot be predicted, the above measurement process needs to be manually adjusted by trial and error according to experience, even if the interferometer is installed with an electrically controlled object table, the quantitative tilt adjustment cannot be automatically realized, and the efficiency of the interferometric measurement of the large warping plane depends on the technology and experience of the operator. At present, there is no systematic sub-aperture distribution planning method.

[0004] Therefore, there is an urgent need for a method for planning the sub-aperture distribution by quantitatively analyzing the warping degree of the plane. SUMMARY

[0005] In order to solve the problems in the prior art, the present application provides a sub-aperture distribution planning method for large warping plane interferometry, which improves the measurement efficiency by quantitatively adjusting the tilt amount of the measured piece in the large warping plane interferometry process.

[0006] Technical scheme:

[0007] The present application discloses a sub-aperture distribution planning method for large warping plane interferometry, comprising:

[0008] An interferometric measurement light path is built, a spatial coordinate system is set, the tilt tolerance and the virtual diaphragm of the interferometer are calibrated according to the focused light spot of the standard plane on the focal plane of the interferometer, and the size of the focal plane sub-aperture is determined;

[0009] According to the focused light spot distribution of the measured piece on the focal plane of the interferometer, the warping light spot and the warping degree of the measured piece are obtained, the number and position of the sub-apertures are set according to the warping light spot, and the tilt compensation amount corresponding to each sub-aperture is calculated.

[0010] In the in-situ splicing process of the sub-aperture, the measured object is adjusted in tilt according to the tilt compensation amount until all the sub-apertures cover the whole measured object, and the interference measurement is completed.

[0011] Further, the spatial coordinate system divides the coordinate space of the interferometer into: a real space (x, y, z) where the measured object is located, a focal plane space where the collimating objective lens of the interferometer focuses, and an image space where the target surface of the interference pattern acquisition CCD is located, wherein the coordinate system of the focal plane is represented as .

[0012] Further, the tilt amount of the measured object in the real space is mapped to the off-axis amount in the focal plane space; the height variation on the plane of the measured object in the real space is mapped to the gray value variation of the upper beam interference in the image space; the spot space distribution of the focal plane space is mapped to the density distribution of the interference fringes in the image space.

[0013] Further, the tilt tolerance calibration process comprises:

[0014] (1) Adjust the standard transmission flat crystal of the interferometer so that the reflected light spot is located at the center of the crosshair reticle, and shoot the background pattern generated by the standard transmission flat crystal on the focal plane;

[0015] (2) Place the standard reflection flat crystal in the real space so that the reflected light spot is located at the center of the crosshair reticle, and adjust the tilt of the standard reflection flat crystal in two orthogonal directions. When the interference pattern is cut or the fringe density reaches the measurement limit, record the focused spot pattern in the focal plane space;

[0016] (3) Subtract the focused spot pattern from the background pattern respectively, and extract the spot at the limit position as the tilt tolerance.

[0017] Further, the calibration process of the virtual diaphragm comprises:

[0018] (1) Calculate the circumscribed circle of the spot obtained in the tilt tolerance calibration process to obtain the diameter d and the center position of the circle.

[0019] (2) Set a safety redundancy coefficient δ = 70% to 90%, take r = δd / 2 as the radius of the virtual diaphragm, and take as the center position of the virtual diaphragm.

[0020] Further, the focal plane spot of the measured object in the virtual diaphragm represents the steepness of the warping in the real space, which is allowed to be obtained in one measurement process. The radius of the focal plane sub-aperture is consistent with the radius r of the virtual diaphragm.

[0021] Further, the quantitative calculation of the warping degree of the measured object comprises:

[0022] Adjust the focal plane spot of the test piece to the center of the field of view, and subtract the background image and the reflected spot of the standard flat crystal to obtain the actual warped spot image S;

[0023] Edge identification is performed on the warped spot S, and its maximum circumcircle diameter D is calculated. Let the focal length of the interferometer collimating objective be f, and the warpage of the measured object be... .

[0024] Furthermore, the calculation of the number of sub-apertures includes:

[0025] If the warped light spot pattern has a regular structure, its diameter R is:

[0026] If R / r≤1, set a sub-aperture to achieve measurement of the warpage of the test piece with a warpage of 20μm~30μm;

[0027] like Four sub-apertures are set, with the distance r between their centers and the center of the warped spot, to achieve the measurement of the warped part of the test piece with a warp of 20μm to 60μm;

[0028] like Seven sub-apertures are defined, one in the center and the other six equally distributed. The distance between the center of each of the six equally distributed sub-apertures and the center of the warped light spot is... This enables the measurement of test pieces with a maximum warpage of 100 μm.

[0029] If the warped spot has an irregular shape, then an m×n equidistant array of sub-apertures with an overlap of k is used to cover the entire warped spot, and then the empty sub-apertures are eliminated as needed.

[0030] Further, definition The light intensity distribution on the focal plane. The distribution of the warp steepness of the measured part on the surface. , The adjustment tilt amount for the tested part is:

[0031]

[0032] In the formula, f is the focal length of the collimating objective lens of the interferometer.

[0033] Furthermore, the calculation of the tilt compensation amount corresponding to each sub-aperture is performed using the position parameters of each sub-aperture. This translates to the amount of adjustment required to move the adjustment frame from its current tilted state to a measurable state for that sub-aperture. , , is represented as:

[0034]

[0035] After the previous sub-aperture k is adjusted in place and measured, the subsequent sub-aperture k+1 is adjusted according to the relative tilt amount change, and the tilt adjustment amount thereof is:

[0036]

[0037] Advantages:

[0038] The present application maps the real space of the phase-shifting interferometer where the measured member is located to the focal plane space, calculates the warping characteristics of the measured member through the characteristics of the focal plane spot, and realizes the warping distribution of the measured member originally existing in the image space of the interference graph, so that the warping distribution of the measured member can be quantitatively analyzed.

[0039] The present application calculates the warping distribution of the measured member, reasonably plans the number and distribution of the sub-apertures in the sub-aperture measurement process, maximally reduces the repeated operation in the measurement process, and significantly improves the efficiency of detecting the large warping plane by using the sub-aperture splicing technology.

[0040] The present application also plans the tilt adjustment requirements of each sub-aperture according to the limiting characteristics of the small aperture diaphragm of the interferometer, provides the number of sub-apertures and the tilt compensation amount of each sub-aperture for the automatic test process of the large warping measured member. Compared with the existing method, the dependence on the experience and technology of the operator is reduced, not only the efficiency and precision of the sub-aperture measurement are improved, but also the interference of human factors is reduced. BRIEF DESCRIPTION OF DRAWINGS

[0041] Figure 1 It is an optical path structure diagram for interference measurement by using a phase-shifting interferometer;

[0042] Figure 2 It is the focal plane spot characteristics of the measured surface with different warping characteristics, wherein (a) is a plane, corresponding to a focal plane is a converging point spot; (b) is a fold surface, corresponding to a focal plane is two or more separated spots; (c) is a quadratic surface, corresponding to a focal plane is an extended elliptical spot; (d) is an irregular warping, corresponding to a focal plane is an irregularly diffused spot;

[0043] Figure 3 It is an example of three simple sub-aperture configurations;

[0044] Figure 4 It is a schematic diagram of spot distribution on the focal plane of the interferometer;

[0045] Figure 5 It is an experimental image collected after the sub-aperture distribution planning of the embodiment of the present application. DETAILED DESCRIPTION

[0046] The present application will be further illustrated in combination with the drawings and specific embodiments.

[0047] This invention discloses a method for planning the sub-aperture distribution of a large warp plane in focal plane space. It leverages the characteristic that beams of different tilts converge at different positions on the focal plane, allowing for direct calculation based on the intensity distribution of the measured object on the focal plane without requiring prior knowledge of the wavefront. Automatically divides sub-apertures and calculates the tilt compensation amount of the tested part. , The following are the specific steps of the method of the present invention.

[0048] (1) Construct the interferometric optical path and set up the spatial coordinate system.

[0049] A schematic diagram of the optical path structure of a phase-shifting interferometer is shown below. Figure 1 As shown, the laser beam emitted by the laser (1.1) is diverged into a spherical wave by the beam expander (1.2), and then output through the collimating objective (1.3) to illuminate the standard reference plane (1.4) and the test piece (1.5). It is then reflected by (1.4) and (1.5) respectively, forming a two-beam interference. The surface position of the test piece is defined as the real space, and its coordinates along the optical axis returning from the collimating wavefront are defined as the z-axis. The returned beam is reflected by the beam splitter (2.1) onto the ground glass screen (2.2) and acquired by the CCD-A (2.3). The ground glass screen is located at the focal point of the collimating objective, and the surface position of the ground glass is defined as the focal plane space. The returned beam passes through the beam splitter (3.1), the pinhole aperture (3.2), and the subsequent imaging system (3.3) to reach the target surface (3.4) of the CCD-B. The CCD-B can acquire the interference image, and the position of this target surface is defined as the image space.

[0050] Let (x,y) be a coordinate system in real space. Let be the pixel coordinate system on the focal plane. The coordinate space of the phase-shifting interferometer is divided into: the real space where the device under test (DUT) is located, the focal plane space where the collimating objective lens focuses, and the image space where the CCD target surface for interferogram acquisition is located. Specifically, the warpage or tilt of the DUT in the real space is mapped to the off-axis value in the focal plane space; the height change of the DUT on the plane in the real space is mapped to the grayscale value change of the upper beam interference in the image space; and the spatial distribution of the light spot in the focal plane space is mapped to the density distribution of the interference fringes in the image space.

[0051] definition For the light intensity distribution on the focal plane, The distribution of the warp steepness of the measured part on the surface. , Let the adjustment tilt amount of the tested part be:

[0052]

[0053] In the formula, f is the focal length of the collimating objective lens of the interferometer. From the formula, it can be seen that the warping steepness of a certain region S... The angle of the light beams caused can be adjusted by adjusting the tilt of the measured object 、 The compensation is performed to return the direction of the reflected light beams to the optical axis.

[0054] As shown in Figure 2 the focal plane spot features of the measured surface with different warping features, wherein (a) is a plane, and the corresponding focal plane is a converging point spot; (b) is a fold surface, and the corresponding focal plane is two or more separated spots; (c) is a quadratic surface, and the corresponding focal plane is an extended elliptical spot; (d) is an irregular warping, and the corresponding focal plane is an irregularly diffused spot. Only when the surface of the measured object is absolutely flat, the focal plane is focused into a point. The spread state of the focal plane spot directly reflects the warping features of the warped surface. However, if the warping steepness of the entire surface changes greatly, the compensation can only be performed step by step, that is, the in-situ sub-aperture stitching. The in-situ refers to that the measured object does not undergo translation and rotation, and only different tilt adjustment amounts are loaded; the sub-aperture refers to that after each tilt adjustment, only part of the reflected light beams can be obtained in one measurement process, and the sub-aperture on the object surface is the different warping steepness regions of the surface of the measured object rather than a fixed shaped region.

[0055] (2) calibrate the tilt tolerance of the interferometer.

[0056] The tilt tolerance is one of the basic features of the interferometer. The tilt refers to the tilt angle between the surface of the measured object and the standard transmission flat crystal. The limit tilt value beyond which the limit measurement cannot be performed is referred to as the tilt tolerance. In the focal plane space, the tilt is manifested as the misalignment of the focused spot of the measured object and the focused point of the standard transmission flat crystal. The tilt limit occurs in any direction, and is generally represented by the positive and negative four limit positions in the x / y two tilt adjustment dimensions.

[0057] In the phase-shifting interferometer, the focal plane has two conjugate positions, one of which is the position of the frosted glass crosshair reticle, and the other of which is the position of the test light beam passing through the physical light barrier. Since it is not easy to collect the light beam passing through the position of the physical light barrier, the image collection of the frosted glass crosshair reticle is used to analyze the focusing distribution of the light beam in the present application. When the focused spot on the frosted glass exceeds a specific range, the actual light beam has been blocked by the physical light barrier and cannot reach the target surface of the CCD, and therefore the specific area on the frosted glass is referred to as a virtual light barrier. In the present application, the size of the focal plane sub-aperture is defined as the size of the virtual light barrier. In the actual measurement step, the tilt amount of the measured object needs to be adjusted in the real space, and each focal plane sub-aperture is adjusted to the virtual light barrier, so that the measurement process of different warping sub-apertures of the measured object can be realized. The specific process includes:

[0058] ①Adjust the standard transmission flat of the interferometer so that its reflection spot is located at the center of the cross reticle, and take the background image generated by the standard transmission flat on the focal plane;

[0059] ②Place the standard reflection flat in the real space so that its reflection spot is located at the center of the cross reticle, and then adjust the tilt of the standard reflection flat in two orthogonal directions, to obtain four focal plane space focusing spot images when the interference pattern is cut or the fringe density reaches the measurement limit;

[0060] ③Subtract the four obtained focusing spot images from the background image respectively, to extract the light spots at the four limit positions, which are the tilt tolerances.

[0061] (3) Calibrate the virtual stop of the interferometer.

[0062] Construct a virtual stop on the ground glass screen at one of the two conjugate positions in the focal plane space, and only the light spot in the virtual stop can reach the image space. The virtual stop is calibrated by the following steps:

[0063] ①Calculate the circumscribed circle of the four light spots calibrated by the tilt tolerance, to obtain the diameter d and the center position ;

[0064] ②Set a safety redundancy coefficient δ = 70% ~ 90%, take r = δd / 2 as the radius of the virtual stop, and as the center position of the virtual stop.

[0065] (4) Obtain the warping characteristics of the measured object.

[0066] Place the measured object in the interference cavity so that its reflection spot is located on the reticle, and set the offset to avoid the interference of the light spot of the standard transmission flat TF. Collect the light spot in the focal plane image, subtract the light spot of the standard transmission flat TF, and obtain the graphic structure reflecting the warping steepness distribution characteristics of the measured object, and the characteristic parameter is the diameter D of the minimum circumscribed circle.

[0067] Quantitatively calculate the warping degree of the measured object, and the background elimination algorithm is adopted, and the steps are as follows:

[0068] ①Drive the two-dimensional tilt adjustment of the measured object stage so that the focal plane light spot of the large warping measured object is located at the center of the field of view;

[0069] ②Take and subtract the background image and the reflection light spot of the standard flat to obtain the actual warping light spot image S;

[0070] ③Edge recognition is performed on the warping light spot S, and the minimum circumscribed circle diameter D is calculated, and if the focal length of the collimating objective lens of the interferometer is f, then the warping degree of the large warping measured object is .

[0071] (5) Divide the sub-aperture.

[0072] The in-situ sub-aperture stitching algorithm requires a certain degree of overlap between two adjacent sub-apertures. The overlap, k, is defined as the ratio of the overlap length on the line connecting the centers of the two sub-apertures to the diameter of the sub-aperture, i.e., k = (2r - L) / 2r, where L is the distance between the centers of the two sub-apertures. The preset overlap k for in-situ sub-aperture stitching is generally between 20% and 30%. Based on the virtual aperture radius r, the graphic structure of the warped spot S, and the minimum circumcircle D obtained in the previous steps, the overlap configuration is determined. The number of sub-apertures is planned according to the configuration, and the position parameters of each sub-aperture in the pixel coordinates of the focal plane are recorded. .like Figure 3 The figures shown represent three simple configurations, specifically:

[0073] If the warped light spot pattern has a regular structure, its diameter R is:

[0074] ① If R / r≤1, set a sub-aperture to achieve measurement of the warpage of the test piece with a warpage of 20μm~30μm;

[0075] ②If Four sub-apertures are set, with their centers denoted by a distance r from the center of the warped spot, such as... Figure 3 As shown in (A), the warpage of the test piece with a warpage of 20μm to 60μm is measured; Figure 3 The overlap of (A) is 0.293;

[0076] ③If Set seven sub-apertures, such as Figure 3 As shown in (B), a sub-aperture is set in the center, and the other six are evenly arranged around it, with a distance of [distance] from the center of the warped light spot. This enables the measurement of test pieces with a warpage of up to 100 μm. Figure 3 The overlap of (B) is 0.134;

[0077] If the warped spot pattern is irregular, then an m×n equidistant array of sub-apertures with an overlap of k is used to cover the entire warped spot, and then the empty sub-apertures are eliminated, such as... Figure 3 (C) shows the result obtained after eliminating the voids in the 4×3 sub-aperture. Figure 3 The overlap of (C) is 0.332.

[0078] (6) Calculate the tilt compensation amount corresponding to each sub-aperture. , .

[0079] Position parameters of each sub-aperture This translates to the amount of adjustment required to move the adjustment frame from its current tilted state to a measurable state for that sub-aperture. , , is expressed as:

[0080]

[0081] After the previous sub-aperture k is adjusted in place and measured, the subsequent sub-aperture k+1 can be adjusted by the relative tilt amount change, and the tilt adjustment amount thereof is:

[0082]

[0083] At this point, the sub-aperture distribution of the interference measurement has been planned, and the tilt position of the measured object is automatically adjusted by the motorized multi-dimensional stage. The planned automatic interference measurement and sub-aperture splicing of the measured object are performed to complete the interference measurement. Compared with the existing method which relies on manual operation of technical personnel, the automatic measurement process of the present application not only improves the efficiency and accuracy of sub-aperture measurement, but also reduces the interference of human factors.

[0084] Next, a Φ300mm aperture wafer interferometer is taken as an example to further illustrate the method of the present application. The Φ300mm aperture interferometer used in this embodiment has a light source wavelength of 632.8nm, a collimating objective lens focal length f=1800mm, a focal plane sampling CCD-A pixel of 2k×2k, an interference pattern sampling CCD-B pixel of 4k×4k, a focusing spot diameter of 1mm, and a pinhole aperture of Φ5mm. Through calculation, the maximum allowed tilt angle in the object space is ±3.8′.

[0085] According to the type test results, the interference fringes density that the interferometer can normally measure is 400lp, which is converted into a maximum tilt angle in the object space of 1.5′. Compared with the results of step 1, it is determined that the radius of the virtual aperture on the focal plane is r=1.5mm, and the center is located at the center of the crosshair, i.e. the reference zero position of the focal plane space, and the coordinates thereof are =(0,0). The focal plane sampling CCD-A parameters are pixel 2k×2k and 3.5μm / pixel, and the actual imaging magnification is 1:10, so the radius of the sub-aperture and the virtual aperture in the collected focal plane image is r=43 pixel. The focal plane background image is collected, and then the triangular measured plane with a warping degree of about 100μm is placed on the object stage, and is coarsely adjusted so that the focal plane spot is all in the crosshair plate. For the convenience of image analysis, the spot avoids the two reflection points of the TF, as shown in Figure 4 .

[0086] After collecting, background elimination, filtering and edge identification of the focus plane spot diagram, the minimum circumscribed circle of the spot distribution is obtained, and the spot radius in the focus plane pixel coordinate system is 2.5 mm, which occupies a radius of R=50 pixel on the target surface. According to r / R=0.86, a four-sub-aperture mode is adopted, and one idle sub-aperture is removed according to the actual situation. The focus plane coordinates of each sub-aperture are calculated and converted into tilt amounts to obtain the adjustment mode required to realize the sub-aperture distribution mode. The control of the objective table is adjusted according to the tilt amount, and the CCD-A and the CCD-B are automatically collected to obtain the experimental pictures and interference patterns of each sub-aperture as shown in Figure 5 , wherein the first row of three pictures are the experimental pictures of the CCD-A sampling the three sub-apertures of the measured plane, and the second row is the corresponding interference patterns. According to the three groups of wave surface data obtained from the three groups of sub-aperture images, Figure 5 , the effective area has overlap and covers the entire measured plane, which can be directly used for subsequent splicing calculation.

Claims

1. A method for sub-aperture distribution planning for large-warp plane interferometry, characterized in that, The application relates to a method for measuring a curved surface of a measured object. The method comprises the following steps: Setting up an interference measurement light path, setting a spatial coordinate system, calibrating a tilt tolerance and a virtual light barrier of an interferometer according to focused light spots of standard planes on a focal plane of the interferometer, and determining the size of a focal plane sub-aperture; According to the focused light spot distribution of the measured object on the focal plane of the interferometer, the warped light spot and the warping degree of the measured object are obtained; the number and position of the sub-apertures are set according to the warped light spot, and the tilt compensation amount corresponding to each sub-aperture is calculated; 2. The sub-aperture distribution planning method of claim 1, wherein, The spatial coordinate system divides the coordinate space of the interferometer into: a real space (x, y, z) where the measured object is located, a focal plane space where the collimating objective of the interferometer focuses, and an image space where the CCD target surface of the interference pattern acquisition is located, wherein the coordinate system of the focal plane is represented as .

3. The sub-aperture distribution planning method of claim 2, wherein, During the in-situ splicing process of the sub-apertures, the measured object is adjusted in tilt according to the tilt compensation amount until all the sub-apertures cover the whole measured object, and the interference measurement is completed.

4. The sub-aperture distribution planning method of claim 3, wherein, The warping tilt amount of the measured object in the real space is mapped into an off-axis amount in the focal plane space; the height change on the plane of the measured object in the real space is mapped into the gray value change of the up-beam interference in the image space; and the light spot spatial distribution in the focal plane space is mapped into the density distribution of the interference fringes in the image space. The calibration process of the tilt tolerance comprises the following steps: (1) adjusting a standard transmission flat crystal of the interferometer so that the reflection point is located at the center of a crosshair reticle, and shooting the background image generated by the standard transmission flat crystal on the focal plane; (2) placing a standard reflection flat crystal in the real space so that the reflection point is located at the center of the crosshair reticle, adjusting the tilt of the standard reflection flat crystal in two orthogonal directions, recording the focused light spot image in the focal plane space when the interference pattern is cut or the fringe density reaches the measurement limit; 5. The sub-aperture distribution planning method of claim 4, wherein, (3) subtracting the focused light spot image from the background image respectively, and extracting the light spot at the limit position as the tilt tolerance. (1) Calculate the circumscribed circle of the light spot obtained in the tilt tolerance calibration process to obtain the diameter d and the center position of the circle ; (2) Set the safety redundancy coefficient δ = 70% ~ 90%, take r = δd / 2 as the virtual diaphragm radius, and take as the virtual diaphragm center position. (3) Set the safety redundancy coefficient δ = 70% ~ 90%, take r = δd / 2 as the virtual diaphragm radius, and take as the virtual diaphragm center position.

6. The sub-aperture distribution planning method of claim 5, wherein, The calibration process of the virtual light barrier comprises the following steps:

7. The sub-aperture distribution planning method of claim 6, wherein, The focal plane light spot of the measured object in the virtual light barrier represents the warping steepness in the real space, and is allowed to be obtained in one measurement process; the radius of the focal plane sub-aperture is consistent with the radius r of the virtual light barrier. The method for obtaining the warped light spot and the warping degree of the measured object comprises the following steps: Edge recognition is performed on the warped light spot S, the maximum circumscribed circle diameter D is calculated, the focal length of the collimator objective of the interferometer is f, and the warping degree of the measured member is .

8. The sub-aperture distribution planning method of claim 7, wherein, Adjusting the focal plane light spot of the measured object to the center of the field of view, eliminating the background image and the reflection light spot of the standard flat crystal through subtraction, and obtaining the actual warped light spot image S; The method for setting the number and position of the sub-apertures comprises the following steps: If the warped light spot has a regular pattern structure, the diameter R is obtained; If Four sub-apertures are set, the center of which is at a distance r from the center of the warping spot, to measure the warping of 20-60 μm of the measured object. If , set seven sub-apertures, one in the center, the remaining six are equally divided, the center of the six equally divided sub-apertures is at a distance of from the center of the warped spot; the measurement of the measured object with a maximum warping of 100 μm is realized. If R / r<=1, one sub-aperture is set to realize the measurement of the measured object with a warping degree of 20-30 mu m; 9. The sub-aperture distribution planning method of claim 8, wherein, Definitions is the light intensity distribution on the focal plane, is the measured member warping steepness distribution on the object plane, , is the adjustment tilt amount of the measured member, and has: If the pattern structure of the warped light spot is irregular, m*n equidistant array sub-apertures with an overlap degree of k are used to cover the whole warped light spot, and the idle sub-apertures are eliminated as required. In the formula, f is the focal length of the collimating objective lens of the interferometer.

10. The sub-aperture distribution planning method of claim 9, wherein, The calculation of the tilt compensation quantity corresponding to each sub-aperture is performed by using the position parameter of each sub-aperture , and converting into the adjustment quantity required for the adjustment frame to transfer from the current tilt state to the measurable state of the sub-aperture 、 , and is expressed as: After the previous sub-aperture k is adjusted to position and the measurement is completed, the following sub-aperture k+1 is adjusted to position with a relative tilt adjustment of , : 。

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