Three-dimensional topography measuring device and method based on double-helical light beams

Abstract

The application provides a three-dimensional topography measuring device and method based on a double helix light beam, and belongs to the technical field of optical three-dimensional topography measurement. The device comprises: a light source module comprising a laser and a liquid crystal element, which is used to generate a composite light beam in which a left-handed circularly polarized component and a right-handed circularly polarized component are superimposed; a reflective topography scanning module comprising a sample to be measured, an objective lens and a first non-polarized light splitting prism; the composite light beam is focused to the surface of the sample to be measured by the objective lens after being reflected by the first non-polarized light splitting prism through the movement of the sample to be measured, and the reflected light from the surface of the sample to be measured is collected by the objective lens; a beam splitting detection module is used to split the collected reflected light, and left-handed circularly polarized state double helix focused light beam intensity images and right-handed circularly polarized state double helix focused light beam intensity images are collected to obtain a three-dimensional topography measurement image of the sample to be measured. The application realizes three-dimensional topography measurement with high measurement precision reaching the sub-nanometer level, high stability and simple structure.

Description

Technical Field

[0001] This invention belongs to the field of optical three-dimensional topography measurement technology, and in particular, relates to a three-dimensional topography measurement device and method based on a double helix beam. Background Technology

[0002] Optical topography measurement technology, with its advantages of non-contact measurement and high integration, is widely used in precision manufacturing, micro-nano fabrication, semiconductor processing, and new energy fields. With the development of semiconductor manufacturing, device feature sizes are continuously decreasing while complexity is increasing, making stacked chips and 3D integrated chips increasingly important development directions. Furthermore, in the precision manufacturing process of semiconductors, the three-dimensional topography of tiny subsurface defects (such as particles, pits, and scratches) is crucial for process control, directly affecting chip yield and performance. Therefore, semiconductor processing requires three-dimensional topography detection methods with sub-nanometer precision and simple structures.

[0003] Commonly used optical measurement methods for three-dimensional topography in semiconductor processing include scanning white light interferometry and spectral confocal microscopy. Scanning white light interferometry offers sub-nanometer precision and a simple structure; however, due to its short depth of focus, it requires three-dimensional scanning of the sample, making the detection speed insufficient for high-speed production. Spectral confocal microscopy requires spectral detection, resulting in a complex optical system, low equipment integration, and a generally micrometer-level precision in height measurement.

[0004] Therefore, as the feature size of semiconductor devices has entered the nanoscale, the speed and sensitivity of three-dimensional morphology detection still need to be improved, and there is an urgent need to achieve three-dimensional morphology measurement with sub-nanometer precision and high stability. Summary of the Invention

[0005] The purpose of this invention is to provide a three-dimensional topography measurement device and method based on a double helix beam, which solves the problem that existing three-dimensional topography measurement images are difficult to achieve sub-nanometer accuracy and high stability.

[0006] According to a first aspect of the present invention, a three-dimensional topography measurement device based on a double-helix beam is provided. The device includes: a light source module comprising a laser and a liquid crystal element for generating a composite beam of double-helix beams superimposed with left-handed and right-handed circularly polarized components; a reflective topography scanning module comprising a sample to be measured, an objective lens, and a first unpolarized beam splitter, and moving the sample to be measured via a stage, wherein the composite beam is reflected by the first unpolarized beam splitter and focused by the objective lens onto the surface of the sample to be measured on the stage, and the objective lens collects the reflected light from the surface of the sample to be measured; and a beam splitting detection module for splitting the collected reflected light into a left-handed and a right-handed circularly polarized component, and simultaneously acquiring an intensity image of the left-handed circularly polarized double-helix focused beam and an intensity image of the right-handed circularly polarized double-helix focused beam; wherein a three-dimensional topography measurement image of the sample to be measured is obtained based on the intensity images of the left-handed and right-handed circularly polarized double-helix focused beams.

[0007] According to a second aspect of the present invention, a three-dimensional topography measurement method based on a double-helix beam is provided for use in the above-mentioned three-dimensional topography measurement device based on a double-helix beam. The method includes: step S1, controlling the stage to move along the optical axis carrying the sample to be measured, and for each axial position, acquiring a left-handed circularly polarized double-helix focused beam intensity image and a right-handed circularly polarized double-helix focused beam intensity image; step S2, overlapping the left-handed circularly polarized double-helix focused beam intensity image and the right-handed circularly polarized double-helix focused beam intensity image at a central position; step S3, rotating the second intensity image by a predetermined step angle while keeping the first intensity image of the left-handed circularly polarized double-helix focused beam intensity image and the right-handed circularly polarized double-helix focused beam intensity image unchanged to obtain multiple rotation angles, wherein each rotation by the predetermined step angle yields one rotation angle; step S4, calculating the first intensity image and the second intensity image for each rotation angle. Step S5: Obtain the cross-correlation curve of the normalized cross-correlation coefficient as a function of the rotation angle based on multiple rotation angles and the corresponding normalized cross-correlation coefficients; Step S6: Perform Gaussian fitting on the main peak corresponding to the maximum value of the two peaks in the cross-correlation coefficient curve to obtain the cross-correlation peak angle; Step S7: Obtain the mapping relationship between the defocus distance and the cross-correlation peak angle based on the cross-correlation peak angle and the defocus distance of the sample under test relative to the focal plane of the objective lens; Step S8: Control the stage to move the sample under test in a plane perpendicular to the optical axis, and for each scanning point of the sample under test, acquire the intensity image of the left-hand circularly polarized double-helix focused beam and the intensity image of the right-hand circularly polarized double-helix focused beam. Repeat steps S2 to S6 to calculate the cross-correlation peak angle of the scanning point, and obtain the defocus distance of each scanning point based on the cross-correlation peak angle and the mapping relationship, thereby obtaining the three-dimensional morphology measurement image of the sample under test.

[0008] The beneficial effects of this invention are as follows:

[0009] (1) By utilizing the geometric phase characteristics of liquid crystal elements, the liquid crystal polymer applies opposite phase modulation to the left-hand circularly polarized state and the right-hand circularly polarized state, thereby generating a double-helix beam with opposite rotation directions during propagation. By synchronously collecting the double-helix beams with opposite rotation directions of the left-hand circularly polarized state and the right-hand circularly polarized state during propagation, the error introduced by the non-ideal double-helix beam to the rotation angle calculation is reduced, the accuracy and stability of the topography measurement are increased, and the axial measurement accuracy reaches the sub-nanometer level;

[0010] (2) It can determine whether the focused light is focused on the region of height change of the sample to be tested, thereby eliminating the measurement results of the region of height change, and reconstructing the complete three-dimensional morphology by interpolating the region of height change, thus avoiding the generation of edge effects;

[0011] (3) The required devices are simple, no spectral measurement is required, it is easy to integrate with the microscopic imaging optical path, and it has good compatibility. The measurement of three-dimensional morphology only requires two-dimensional movement of the stage, the measurement is fast, and the data processing method is simple. Attached Figure Description

[0012] The accompanying drawings are provided to further illustrate embodiments of the present invention and form part of the specification. They are used together with the following detailed description to explain the embodiments of the present invention, but do not constitute a limitation thereof. In the drawings:

[0013] Figure 1 A schematic diagram of the structure of the three-dimensional topography measurement device based on a double-helix beam provided by the present invention;

[0014] Figure 2 A schematic flowchart of the three-dimensional topography measurement method based on a double-helix beam provided by the present invention;

[0015] Figure 3 A mapping relationship between the cross-correlation peak angle and the defocus distance of the stage in the optical axis direction for different defocus distances provided in the embodiments of the present invention;

[0016] Figure 4 This invention provides a statistical distribution chart of measurements taken at the same defocus distance, as shown in the embodiments of the invention.

[0017] Figure 5 The three-dimensional topographic measurement image of the rectangular groove provided in the embodiment of the present invention;

[0018] Figure 6 These are marked images of the height abrupt change region of the rectangular groove and the reconstructed three-dimensional topographic measurement images, as described in this embodiment of the invention. Figure 6 In the figure, (a) represents the fitting coefficient R for the rectangular groove. 2 Distribution image, Figure 6 Image (b) is a labeled image of the region where the height of the rectangular groove changes abruptly. Figure 6 (c) in the image is the reconstructed three-dimensional topographic measurement image of the rectangular groove.

[0019] Explanation of reference numerals in the attached figures:

[0020] 1. Laser; 2. Liquid crystal element; 3. Sample to be tested; 4. Objective lens; 5. First unpolarized beam splitter prism; 6. Second unpolarized beam splitter prism; 7. First quarter-wave plate; 8. First linear polarizer; 9. First mirror; 10. Second mirror; 11. Second quarter-wave plate; 12. Second linear polarizer; 13. Third unpolarized beam splitter prism; 14. Lens; 15. Area array detector. Detailed Implementation

[0021] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other. To achieve the above objectives, this invention adopts the following technical solution.

[0022] Figure 1 This is a schematic diagram of the structure of the three-dimensional topography measurement device based on a double-helix beam provided by the present invention, as shown below. Figure 1 As shown, the device includes: a light source module, including a laser 1 and a liquid crystal element 2, for generating a composite beam superimposed from double helical beams generated by left-handed and right-handed circularly polarized components respectively; a reflective morphology scanning module, including a sample 3 to be tested, an objective lens 4, and a first unpolarized beam splitter 5, which carries the sample 3 to be tested and moves it via a stage. The composite beam is reflected by the first unpolarized beam splitter 5 and focused by the objective lens 4 onto the surface of the sample 3 on the stage, and the reflected light from the surface of the sample 3 is collected by the objective lens 4; a beam splitting detection module, for splitting the collected reflected light into left-handed and right-handed circularly polarized components, and simultaneously acquiring the intensity images of the left-handed and right-handed circularly polarized double helical focused beams; wherein, a three-dimensional morphology measurement image of the sample 3 to be tested is obtained based on the intensity images of the left-handed and right-handed circularly polarized double helical focused beams.

[0023] In the light source module, the linearly polarized parallel light output by the laser 1 is incident on the liquid crystal element 2. The linearly polarized parallel light is modulated by the liquid crystal element 2 to form a composite beam in which the left-hand circularly polarized component and the right-hand circularly polarized component are superimposed.

[0024] The liquid crystal element 2 uses circularly polarized light as the basis vector and generates a double helical beam with two main lobes separated based on the left-hand circularly polarized component and the right-hand circularly polarized component. The two main lobes rotate as the propagation changes.

[0025] The liquid crystal element 2 adopts a three-dimensional phase recovery algorithm. Based on the distribution of the composite beam of the double helix beams of the left-hand circularly polarized component and the right-hand circularly polarized component at different defocus positions, the phase parameters of the liquid crystal element 2 are optimized.

[0026] The liquid crystal element 2 is made of a liquid crystal polymer. The geometric phase characteristics of the liquid crystal polymer are such that the phase of the left-hand circularly polarized component is opposite to the phase of the right-hand circularly polarized component, so that when the left-hand circularly polarized component and the right-hand circularly polarized component are incident, the liquid crystal element 2 modulates the left-hand circularly polarized component and the right-hand circularly polarized component into double-helix beams with opposite directions of propagation rotation.

[0027] Specifically, the phase distribution of the liquid crystal element 2 is designed based on a three-dimensional phase retrieval algorithm. Due to the geometric phase characteristics of the liquid crystal polymer, the left-hand circularly polarized component and the right-hand circularly polarized component obtain opposite phase modulations under the control of the liquid crystal element 2. The linearly polarized parallel light output from the laser 1 of the light source module is used as the superposition of the left-hand circularly polarized component and the right-hand circularly polarized component. Through the liquid crystal element 2, a composite beam is generated by the superposition of the double-helix beams of the left-hand circularly polarized component and the right-hand circularly polarized component with opposite directions of rotation during propagation.

[0028] The beam splitting detection module includes a second unpolarized beam splitter 6, a first quarter-wave plate 7, a first linear polarizer 8, a first reflector 9, a second reflector 10, a second quarter-wave plate 11, a second linear polarizer 12, a third unpolarized beam splitter 13, a lens 14, and an array detector 15. The reflected light collected by the objective lens 4 passes through the objective lens 4 and exits as parallel light through the rear pupil of the objective lens 4. After being transmitted through the first unpolarized beam splitter 5, it enters the second unpolarized beam splitter 6 and is split into two parallel beams of equal power and the same polarization state. The first parallel beam is the transmitted light from the second unpolarized beam splitter 6, and the second parallel beam is the reflected light from the second unpolarized beam splitter 6. The first parallel beam passes sequentially through the first quarter-wave plate 7 and the first linear polarizer 8 to obtain a left-hand circularly polarized component. The left-hand circularly polarized component is then reflected by the first reflector... The second beam of parallel light is incident on the third unpolarized beam splitter 13. After being reflected by the second mirror 10, the second beam passes through the second quarter-wave plate 11 and the second linear polarizer 12 to obtain a right-hand circularly polarized component. The right-hand circularly polarized component is incident on the third unpolarized beam splitter 13. The left-hand circularly polarized component and the right-hand circularly polarized component are combined by the third unpolarized beam splitter 13 and focused by the lens 14 onto the area array detector 15. The area array detector 15 acquires the intensity images of the left-hand circularly polarized double-helix focused beam and the right-hand circularly polarized double-helix focused beam. When the beam is combined by the third unpolarized beam splitter 13, the first mirror 9 is adjusted to make the double-helix focused beams of the left-hand circularly polarized component and the right-hand circularly polarized component spatially misaligned on the imaging surface of the area array detector 15, so as to simultaneously acquire and distinguish the intensity images of the left-hand circularly polarized double-helix focused beam and the right-hand circularly polarized double-helix focused beam.

[0029] Figure 2 This is a flowchart illustrating the three-dimensional topography measurement method based on a double-helix beam provided by the present invention. This method is used in the three-dimensional topography measurement device based on a double-helix beam provided by the present invention, such as... Figure 2 As shown, the method includes:

[0030] Step S1: Control the stage to move the sample 3 to be tested along the optical axis. For each axial position, acquire the intensity image of the left-hand circularly polarized double-helix focused beam and the intensity image of the right-hand circularly polarized double-helix focused beam.

[0031] Step S2: Overlay the intensity images of the left-hand circularly polarized double-helix focused beam and the right-hand circularly polarized double-helix focused beam at the center position;

[0032] Step S3: While keeping the first intensity image in the left-hand circularly polarized double-helix focused beam intensity image and the right-hand circularly polarized double-helix focused beam intensity image unchanged, rotate the second intensity image by a predetermined step angle to obtain multiple rotation angles. Each rotation by the predetermined step angle yields one rotation angle.

[0033] Step S4: Calculate the normalized cross-correlation coefficient of the first intensity image and the second intensity image for each rotation angle;

[0034] Step S5: Obtain the cross-correlation curve of normalized cross-correlation coefficient as a function of rotation angle based on multiple rotation angles and corresponding normalized cross-correlation coefficients.

[0035] Step S6: Gaussian fitting is performed on the main peak corresponding to the maximum value of the two peaks in the cross-correlation curve to obtain the cross-correlation peak angle.

[0036] Step S7: Based on the cross-correlation peak angle and the defocus distance of the sample 3 relative to the focal plane of the objective lens 4, obtain the mapping relationship between the defocus distance and the cross-correlation peak angle.

[0037] Step S8: Control the stage to move the sample 3 under test in a plane perpendicular to the optical axis. For each scanning point of the sample 3 under test, acquire the intensity image of the left-hand circularly polarized double-helix focused beam and the intensity image of the right-hand circularly polarized double-helix focused beam. Repeat steps S2 to S6 to calculate the cross-correlation peak angle of the scanning point. Based on the cross-correlation peak angle and mapping relationship of the scanning point, obtain the defocus distance of each scanning point, thereby obtaining the three-dimensional morphology measurement image of the sample 3 under test.

[0038] Step S7 includes: moving the sample 3 to be tested along the optical axis multiple times using a stage to obtain multiple defocus distances of the sample 3 relative to the focal plane of the objective lens 4. After each movement, steps S2 to S6 are repeated to calculate multiple cross-correlation peak angles. The multiple defocus distances correspond one-to-one with the multiple cross-correlation peak angles. The correspondence between the multiple defocus distances and the multiple cross-correlation peak angles is linearly fitted to obtain the mapping relationship between the defocus distances and the cross-correlation peak angles.

[0039] Specifically, the intensity images of the left-hand circularly polarized double-helix focused beam and the right-hand circularly polarized double-helix focused beam simultaneously acquired by the area array detector 15 are saved to the computer, and the center positions of the left-hand circularly polarized double-helix focused beam and the right-hand circularly polarized double-helix focused beam are calculated respectively.

[0040] Using the center of the intensity image of the left-hand circularly polarized double-helix focused beam as the center, a circular region of a specified radius is extracted from the intensity images of the left-hand circularly polarized double-helix focused beam and the right-hand circularly polarized double-helix focused beam as the analysis region.

[0041] Based on the analysis region, the intensity images of the left-hand circularly polarized double-helix focused beam and the right-hand circularly polarized double-helix focused beam are superimposed at the center position. While keeping the first intensity images in both images unchanged, the second intensity images in both images are rotated from 0° to 360° with a predetermined step angle to obtain multiple rotation angles. For each rotation angle after the predetermined step angle, the normalized cross-correlation (NCC) between the first and second intensity images is calculated.

[0042] (1)

[0043] in, , For the first intensity image, the first The intensity value of each pixel. The average intensity of the first intensity image. , For the second intensity image The intensity value of each pixel. The average intensity of the second intensity image. The denominator is a constant, and to prevent the denominator from being 0, it is set to 10. -12 , For the index of the pixels in the first intensity image and the second intensity image, The total number of pixels in the first intensity image or the second intensity image, wherein the total number of pixels in the first intensity image is the same as the total number of pixels in the second intensity image.

[0044] A normalized cross-correlation coefficient (NCC) of 1 indicates that the intensity images of a left-handed circularly polarized double-helix focused beam and a right-handed circularly polarized double-helix focused beam are identical. The cross-correlation coefficient curves of the first and second intensity images as a function of the rotation angle are calculated according to formula (1). Within the rotation range of 0° to 360°, the cross-correlation coefficient curves exhibit two peaks. Gaussian fitting is performed on the main peak corresponding to the maximum value of the two peaks to obtain the cross-correlation peak angle.

[0045] The sample 3 is moved along the optical axis by the stage, and the distance between the sample 3 and the focal plane of the objective lens 4 is the defocus distance. The above process of calculating the cross-correlation peak angle is repeated. Figure 3 This is a mapping diagram of the cross-correlation peak angle and defocus distance of the stage along different defocus distances in the optical axis direction, provided in an embodiment of the present invention. Figure 3 As shown, a linear fit was performed to obtain the cross-correlation peak angle. The mapping relationship with the defocus distance z is expressed as follows: Wherein, k and b are obtained by linear fitting of the correspondence between multiple defocus distances and multiple cross-correlation peak angles. This invention collects 4000 images at the same location, averages every 10 images, calculates the defocus distance, and performs Gaussian fitting. The statistical distribution results are as follows: Figure 4 As shown, Figure 4 The measurement statistics distribution diagram for measuring the same defocus distance provided in the embodiment of the present invention has a standard deviation of 0.10 nm for the defocus distance, and the measurement accuracy of the defocus distance in the embodiment of the present invention is in the sub-nanometer range.

[0046] After determining the mapping relationship, the stage is controlled to move the sample 3 under test in two dimensions in a plane perpendicular to the optical axis. Steps S2 to S6 are repeated for each scanning point of the sample 3 under test (it should be understood that the scanning point is preset). The cross-correlation peak angle of the scanning point is calculated. The defocus distance of each scanning point is obtained according to the cross-correlation peak angle of the scanning point and the determined mapping relationship, thereby obtaining a three-dimensional morphology measurement image of the sample 3 under test.

[0047] When the light beam is focused on a region of abrupt change in height of the sample under test, an edge effect will occur. To avoid the influence of the region of abrupt change in height on the measurement results, the three-dimensional topography measurement method based on a double-helix beam provided by this invention further includes: fitting the cross-correlation coefficient curve with a sine function and calculating the fitting determination coefficient R. 2 ; in the fit determination coefficient R 2 When the coefficient is less than a preset threshold, the scanning point corresponding to the fitting determination coefficient is determined to be in a region of high abrupt change, and the corresponding defocus distance is discarded. The three-dimensional morphology measurement image of the region of high abrupt change is reconstructed by interpolation, thereby obtaining a complete three-dimensional morphology measurement image of the sample 3 under test. For example, the range of the coefficient threshold is 0.95-0.99, and preferably, the coefficient threshold can be set to 0.98.

[0048] Among them, the coefficient of determination R 2 When the coefficient is greater than or equal to a preset threshold, the scan point corresponding to the fitting determination coefficient that is greater than or equal to the threshold is determined to be not in a highly abrupt region.

[0049] In one embodiment of the present invention, a rectangular groove is etched on a silicon wafer using focused ion beam technology. Figure 5 The three-dimensional topographic measurement image of the rectangular groove provided in the embodiment of the present invention is as follows: Figure 5 As shown, Figure 5 The x-axis and y-axis represent the coordinates of the scanning area in a two-dimensional plane perpendicular to the optical axis, and the height is the shortest distance from the scanning point to the objective lens focal plane. Figure 5 The colors of the grayscale bar chart on the right side represent the heights corresponding to the two-dimensional scanning points of the sample under test.

[0050] When the beam is focused on the highly abrupt region of the sample under test, an edge effect will occur. To avoid the influence of the highly abrupt region on the measurement results, a sinusoidal function is fitted to the cross-correlation curve, and the fitting determination coefficient R is used. 2 As a discriminant metric, the coefficient of determination R in this embodiment is used. 2 The coefficient of determination R is 0.98. 2 A value greater than or equal to 0.98 indicates that the corresponding two-dimensional scan point is not located at the edge of the groove, and the fitting determination coefficient R0 is... 2 If the value is less than 0.98, the corresponding two-dimensional scanning point is determined to be located at the edge of the groove, and the morphological measurement results of the corresponding two-dimensional scanning point are discarded accordingly.

[0051] Figure 6 These are marked images of the height abrupt change region of the rectangular groove and the reconstructed three-dimensional topographic measurement images, as described in this embodiment of the invention. Figure 6 In the figure, (a) represents the fitting coefficient R for the rectangular groove. 2 Distribution image, Figure 6 Image (b) shows the labeled image of the height abrupt change region of the rectangular groove, with black representing the identified height abrupt change region. Figure 6 Image (c) in the image is the reconstructed three-dimensional topographic measurement image of the rectangular groove. Figure 6 The x-axis and y-axis are the coordinates of the scanning area in a two-dimensional plane perpendicular to the optical axis. The two-dimensional distribution of the coefficients of determination of the sine function fitting the cross-correlation curve of the rectangular groove is shown in the figure. Figure 6 As shown in (a), the coefficient of determination R is... 2 When the value is less than 0.98, the beam is considered to be focused on the edge region of the groove (i.e., the region of abrupt height change), such as... Figure 6 As shown in (b), the black area represents the discriminated groove edge region. The out-of-focus distance of the groove edge region is removed, and interpolation reconstruction is performed on the groove edge region to reconstruct a complete three-dimensional topographic measurement image of the rectangular groove. The measured three-dimensional topographic distribution of the rectangular groove is as follows: Figure 6 As shown in (c), the height represents the height corresponding to the two-dimensional scanning position of the sample 3 under test. Figure 6 The grayscale change bar chart on the right represents the height corresponding to the scanning point of sample 3.

[0052] The 3D topography measurement device and method based on a double-helix beam provided by this invention reduces the error introduced by the imperfections of the double-helix beam in the calculation of rotation angles, increases the accuracy and stability of topography measurement, achieves sub-nanometer level height measurement accuracy, and can identify whether the double-helix beam is focused on a region of abrupt height change (such as the edge of a groove) to avoid the influence of edge effects on the measurement image. Interpolation reconstruction is performed on the region of abrupt height change to obtain a complete 3D topography measurement image. This invention features sub-nanometer level longitudinal measurement accuracy and high stability, and is suitable for topography measurement and defect detection in semiconductor processing and precision manufacturing.

[0053] The optional embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the embodiments of the present invention are not limited to the specific details in the above embodiments. Within the scope of the technical concept of the embodiments of the present invention, various simple modifications can be made to the technical solutions of the embodiments of the present invention, and these simple modifications all fall within the protection scope of the embodiments of the present invention.

[0054] It should also be noted that the various specific technical features described in the above embodiments can be combined in any suitable manner without contradiction. To avoid unnecessary repetition, the embodiments of the present invention will not describe the various possible combinations separately.

[0055] Furthermore, various different implementations of the present invention can be combined arbitrarily, as long as they do not violate the spirit of the present invention, they should also be regarded as the content disclosed in the present invention.

Claims

1. A three-dimensional topography measurement device based on a double-helix beam, characterized in that, The device includes: The light source module includes a laser (1) and a liquid crystal element (2) for generating a composite beam of a double helical beam with a left-hand circularly polarized component and a right-hand circularly polarized component superimposed. The reflective morphology scanning module includes a sample to be tested (3), an objective lens (4) and a first non-polarizing beam splitter (5). The sample to be tested (3) is moved by a stage. The composite beam is reflected by the first non-polarizing beam splitter (5) and focused by the objective lens (4) onto the surface of the sample to be tested (3) on the stage. The reflected light from the surface of the sample to be tested (3) is collected by the objective lens (4). The beam splitting detection module is used to split the collected reflected light into a left-hand circularly polarized component and a right-hand circularly polarized component, and simultaneously acquire the intensity images of the left-hand circularly polarized double-helix focused beam and the right-hand circularly polarized double-helix focused beam. Among them, the three-dimensional morphology measurement image of the sample to be tested (3) is obtained based on the intensity image of the left-hand circularly polarized double helix focused beam and the intensity image of the right-hand circularly polarized double helix focused beam; The beam splitting detection module includes a second unpolarized beam splitter prism (6), a first quarter-wave plate (7), a first linear polarizer (8), a first reflector (9), a second reflector (10), a second quarter-wave plate (11), a second linear polarizer (12), a third unpolarized beam splitter prism (13), a lens (14), and an area array detector (15), wherein: The reflected light collected by the objective lens (4) passes through the objective lens (4) and exits as parallel light through the rear pupil of the objective lens (4). After being transmitted through the first non-polarizing beam splitter (5), it enters the second non-polarizing beam splitter (6) and is split into two parallel beams with equal power and the same polarization state by the second non-polarizing beam splitter (6). The first parallel beam is the transmitted light of the second non-polarizing beam splitter (6), and the second parallel beam is the reflected light of the second non-polarizing beam splitter (6). The first beam of parallel light passes through the first quarter-wave plate (7) and the first linear polarizer (8) in sequence to obtain a left-hand circularly polarized component. The left-hand circularly polarized component is incident on the third unpolarized beam splitter (13) through the first reflecting mirror (9). The second beam of parallel light is reflected by the second mirror (10) and then passes through the second quarter-wave plate (11) and the second linear polarizer (12) to obtain a right-hand circularly polarized component. The right-hand circularly polarized component is incident on the third unpolarized beam splitter (13). The left-hand circularly polarized component and the right-hand circularly polarized component are combined by the third non-polarizing beam splitter (13) and focused by the lens (14) onto the array detector (15). The array detector (15) then acquires the intensity images of the left-hand circularly polarized double-helix focused beam and the right-hand circularly polarized double-helix focused beam. In this process, when the third non-polarizing beam splitter (13) combines the beams, the first reflecting mirror (9) is adjusted to make the double-helix focused beams of the left-hand circularly polarized component and the right-hand circularly polarized component spatially misaligned on the imaging surface of the array detector (15), so as to simultaneously acquire and distinguish the intensity images of the left-hand circularly polarized double-helix focused beam and the right-hand circularly polarized double-helix focused beam.

2. The three-dimensional topography measurement device based on a double-helix beam according to claim 1, characterized in that, In the light source module, the laser (1) outputs linearly polarized parallel light that is incident on the liquid crystal element (2). The linearly polarized parallel light is modulated by the liquid crystal element (2) to form a composite beam of double helix beams with left-hand circular polarization component and right-hand circular polarization component superimposed.

3. The three-dimensional topography measurement device based on a double-helix beam according to claim 2, characterized in that, The liquid crystal element (2) uses circularly polarized light as the basis vector and generates a double helical beam with two main lobes separated based on the left-hand circularly polarized component and the right-hand circularly polarized component. The two main lobes rotate as the propagation distance changes.

4. The three-dimensional topography measurement device based on a double-helix beam according to claim 3, characterized in that, The liquid crystal element (2) adopts a three-dimensional phase recovery algorithm. Based on the distribution of the composite beam of the superimposed double helix beam of the left-hand circular polarization component and the right-hand circular polarization component at different defocus positions, the phase parameters of the liquid crystal element (2) are optimized.

5. The three-dimensional topography measurement device based on a double-helix beam according to claim 4, characterized in that, The liquid crystal element (2) is made of a liquid crystal polymer. The geometric phase characteristics of the liquid crystal polymer are such that the phase of the left-hand circularly polarized component is opposite to the phase of the right-hand circularly polarized component, so that when the left-hand circularly polarized component and the right-hand circularly polarized component are incident, the liquid crystal element (2) controls the left-hand circularly polarized component and the right-hand circularly polarized component into double-helix beams with opposite directions of propagation rotation.

6. A three-dimensional topography measurement method based on a double-helix beam, used in the three-dimensional topography measurement device based on a double-helix beam as described in claim 5, characterized in that, The method includes: Step S1: Control the stage to move along the optical axis along the optical axis carrying the sample to be tested (3). For each axial position, acquire the intensity image of the left-hand circularly polarized double helix focused beam and the intensity image of the right-hand circularly polarized double helix focused beam. Step S2: Overlay the intensity images of the left-hand circularly polarized double-helix focused beam and the right-hand circularly polarized double-helix focused beam at the center position; Step S3: While keeping the first intensity image in the left-hand circularly polarized double-helix focused beam intensity image and the right-hand circularly polarized double-helix focused beam intensity image unchanged, rotate the second intensity image by a predetermined step angle to obtain multiple rotation angles. Each rotation by the predetermined step angle yields one rotation angle. Step S4: Calculate the normalized cross-correlation coefficient of the first intensity image and the second intensity image for each rotation angle; Step S5: Obtain the cross-correlation curve of normalized cross-correlation coefficient as a function of rotation angle based on multiple rotation angles and corresponding normalized cross-correlation coefficients. Step S6: Gaussian fitting is performed on the main peak corresponding to the maximum value of the two peaks in the cross-correlation curve to obtain the cross-correlation peak angle. Step S7: Based on the cross-correlation peak angle and the defocus distance of the sample (3) relative to the focal plane of the objective lens (4), obtain the mapping relationship between the defocus distance and the cross-correlation peak angle; Step S8: Control the stage to move the sample (3) to be tested in a plane perpendicular to the optical axis. For each scanning point of the sample (3), acquire the intensity image of the left-hand circularly polarized double helix focused beam and the intensity image of the right-hand circularly polarized double helix focused beam. Repeat steps S2 to S6 to calculate the cross-correlation peak angle of the scanning point. Based on the cross-correlation peak angle and mapping relationship of the scanning point, obtain the defocus distance of each scanning point, thereby obtaining the three-dimensional morphology measurement image of the sample (3) to be tested.

7. The three-dimensional topography measurement method based on a double-helix beam according to claim 6, characterized in that, Step S7 includes: The sample to be tested (3) is moved multiple times along the optical axis by the stage to obtain multiple defocus distances of the sample to be tested (3) relative to the focal plane of the objective lens (4). After each movement, the calculation is repeated by step S2 to step S6 to obtain multiple cross-correlation peak angles. The multiple defocus distances correspond one-to-one with the multiple cross-correlation peak angles. The mapping relationship between the defocus distances and the cross-correlation peak angles is obtained by linear fitting of the correspondence between the multiple defocus distances and the multiple cross-correlation peak angles.

8. The three-dimensional topography measurement method based on a double-helix beam according to claim 7, characterized in that, The method also includes: The cross-correlation coefficient curve is fitted with a sinusoidal function, and the coefficient of determination is calculated. When the fitting determination coefficient is less than the preset coefficient threshold, the scan point corresponding to the fitting determination coefficient less than the coefficient threshold is determined to be in a high abrupt change region, and the corresponding defocus distance is discarded. The three-dimensional topographic measurement image of the highly abrupt region is reconstructed by interpolation.

9. The three-dimensional topography measurement method based on a double-helix beam according to claim 8, characterized in that, The range of the coefficient threshold is 0.95-0.99.

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