A vortex light interference alignment measurement system and detection method based on grating secondary diffraction

Abstract

The application discloses a vortex light interference alignment measurement system based on grating secondary diffraction, which uses a phase grating as a silicon wafer alignment mark, and an alignment light source, a polarizer and a polarization beam splitter are arranged on an incident light path; a vortex phase plate, a quarter-wave plate and a mirror are arranged on each secondary diffraction light path; and a detector is arranged on a detection light path; the detector receives secondary diffraction light based on phase grating diffraction and causes interference to form an interference pattern. The application further discloses a detection method applied to the system. The application can realize high-precision detection of a silicon wafer alignment mark position, the precision of position detection resolution can reach 0.2 nm, and the light path structure is simple, and various optical devices are easy to assemble and adjust.

Description

Technical Field

[0001] This invention belongs to the field of photolithography technology, specifically relating to a vortex light interferometry alignment measurement system and detection method based on grating secondary diffraction. Background Technology

[0002] In integrated circuit manufacturing using projection lithography, up to hundreds of lithography exposure processes are required to precisely transfer different mask patterns layer by layer to corresponding positions on the silicon wafer, thereby obtaining the complex three-dimensional structure of the integrated circuit. During this process, the lithography machine needs to have very high overlay accuracy, which is a core performance indicator. This indicator quantifies the positional deviation between the newly exposed circuit pattern and the previous layer during lithography. In immersion, extreme ultraviolet (EUV), and high numerical aperture (High-NA) EUV lithography, to achieve precise manufacturing of the complex three-dimensional structure of integrated circuits, the overlay accuracy must be controlled within 2nm. The silicon wafer alignment measurement error accounts for approximately one-third of the total overlay error budget.

[0003] To achieve high-precision measurement in lithography machine alignment sensing systems, phase gratings are typically used as alignment markers. Therefore, the sensitivity of the alignment sensing system to minute offsets in the alignment marker position is a crucial factor determining measurement accuracy. Existing alignment sensing systems usually utilize interference signals between different orders of light obtained from phase grating diffraction to detect the phase grating position. These alignment sensing schemes all employ only single-order diffraction light from the phase grating, thus limiting the measurement sensitivity of the alignment sensing system.

[0004] For example, US2004033426A1 discloses a photolithography apparatus, a device manufacturing method, and a device manufactured by the method. This invention uses a self-reference interferometer to generate two overlapping and relatively rotated images of alignment marks. A detector detects intensity in a pupil plane where the Fourier transforms of the images interfere. Position information is derived from the phase difference between the diffraction orders of the two images, which manifests as a change in the intensity of the interference signal.

[0005] For example, US2018149987A1 discloses an alignment system that can be used as a component of a photolithography apparatus to detect the position of alignment marks in order to support the alignment requirements of the photolithography process. The alignment system includes: a first system that generates two overlapping images of the alignment marks, wherein the two images are rotated relative to each other by about 180 degrees; and a second system that calculates the position of the alignment marks based on the spatial distribution of light intensity of the two overlapping images. Summary of the Invention

[0006] The purpose of this invention is to provide a vortex light interferometric alignment measurement system and detection method based on grating secondary diffraction. The system uses a phase grating as a silicon wafer alignment mark and performs secondary diffraction of vortex light to achieve high-precision detection of the position of the silicon wafer alignment mark. The system has a simple optical path structure and is easy to operate.

[0007] This invention provides a vortex optical interferometry alignment measurement system based on grating secondary diffraction, employing a phase grating as a silicon wafer alignment mark. The silicon wafer alignment mark includes a first grating and a second grating. The vortex optical interferometry alignment measurement system comprises: A polarization beam splitter is located directly above the silicon wafer alignment mark; The incident light path includes an alignment light source and a polarizer. The incident light emitted from the alignment light source passes through the polarizer and exits as a beam parallel to the plane where the alignment mark on the silicon wafer is located. After being reflected by the polarizing beam splitter, it is perpendicularly irradiated to the alignment mark on the silicon wafer and diffracted to generate primary diffracted light. The primary diffracted light is divided into positive first-order diffracted light and negative first-order diffracted light in the x-direction and positive first-order diffracted light and negative first-order diffracted light in the y-direction according to the detection direction. The secondary diffraction optical path is divided into a positive first-order secondary diffraction optical path and a negative first-order secondary diffraction optical path in the x-direction and a positive first-order secondary diffraction optical path and a negative first-order secondary diffraction optical path in the y-direction, according to the detection direction. Each secondary diffraction optical path is equipped with a vortex phase plate, a quarter-wave plate and a reflector. In the same detection direction, the primary diffracted light passes through the vortex phase plate and the quarter-wave plate in sequence, is reflected by the reflector, passes through the quarter-wave plate and the vortex phase plate again and is incident on the alignment mark of the silicon wafer and diffracted to generate secondary diffracted light. The detection optical path includes a detector. After the secondary diffracted beams are combined, they pass through the polarization beam splitter and are received by the detector, where they interfere to form an interference pattern.

[0008] Furthermore, the silicon wafer alignment mark is composed of a reflective phase grating.

[0009] Furthermore, the first grating is used for detecting the position of the silicon wafer alignment mark in the x direction, with the scribe line direction along the y direction; the second grating is used for detecting the position of the silicon wafer alignment mark in the y direction, with the scribe line direction along the x direction. In the global coordinate system of the projection lithography machine, x and y are the horizontal and vertical directions of the horizontal plane, respectively, and the z-axis is perpendicular to the xy plane.

[0010] When the vortex optical interferometry alignment measurement system detects the x-direction position of the silicon wafer alignment mark, the light beam illuminates the first grating used for x-direction position detection, generating positive and negative first-order diffraction light. When the vortex optical interferometry alignment measurement system detects the y-direction position of the silicon wafer alignment mark, the light beam illuminates the second grating used for y-direction position detection, generating positive and negative first-order diffraction light. The x-direction and y-direction position detections are not performed synchronously, so only two diffraction lights can be generated at a time. The x-direction and y-direction are two mutually perpendicular and orthogonal directions on the horizontal plane of the global coordinate system of the projection lithography machine.

[0011] Furthermore, the detection optical path includes a beam expander located above the detector. The beam expander includes a first lens and a second lens. The distance between the first lens and the second lens is the sum of the focal lengths of the two lenses. The magnification of the beam expander is the ratio of the focal lengths of the first lens and the second lens.

[0012] The present invention also provides a detection method using the above-mentioned vortex optical interferometry alignment measurement system based on grating secondary diffraction, as shown below: S1. Determine the detection direction of the silicon wafer alignment mark. According to the detection direction, the incident light emitted by the alignment light source passes through the polarizer and exits as a beam parallel to the plane where the silicon wafer alignment mark is located. After being reflected by the polarization beam splitter, it is perpendicularly irradiated to the silicon wafer alignment mark and diffracted to generate first-order diffracted light. The first-order diffracted light is divided into positive first-order diffracted light and negative first-order diffracted light in the detection direction. The first-order diffracted light passes through the vortex phase plate and the quarter-wave plate in sequence, and is reflected by the mirror. It then passes through the quarter-wave plate and the vortex phase plate again and is incident on the silicon wafer alignment mark and diffracted to generate second-order diffracted light. The beams of the second-order diffracted light are combined and pass through the polarization beam splitter. The beams are received by the detector and interfere to form an interference pattern. S2. Calculate the rotation angle between the interference pattern and the reference pattern; the reference pattern is the interference pattern detected on the detector surface when the silicon wafer alignment mark position offset is 0 (pre-obtained); S3. Calculate the position offset of the silicon wafer alignment mark based on the rotation angle between the interference pattern and the reference pattern.

[0013] Furthermore, the detection direction of the silicon wafer alignment mark is divided into the x-direction and the y-direction; Furthermore, when the detection direction of the silicon wafer alignment mark is the x-direction, the incident light emitted by the alignment light source along the x-direction passes through the polarizer and exits as a beam with a polarization direction perpendicular to the xz plane. After being reflected by the polarization beam splitter, it vertically illuminates the first grating of the silicon wafer alignment mark and diffracts to generate positive first-order diffracted light and negative first-order diffracted light in the x-direction. The positional deviation is calculated based on the rotation angle between the interference pattern obtained when the detection direction is x-axis and the reference pattern. for: ; in, The grating period corresponding to the first grating of the silicon wafer alignment mark. Let be the rotation angle of the interference pattern relative to the reference pattern. denoted as the topological load number.

[0014] Furthermore, when the detection direction of the silicon wafer alignment mark is the y direction, the incident light emitted by the alignment light source along the x direction passes through the polarizer and exits as a beam with a polarization direction perpendicular to the xz plane. After being reflected by the polarization beam splitter, it vertically illuminates the second grating of the silicon wafer alignment mark and diffracts to generate positive first-order diffracted light and negative first-order diffracted light in the y direction. The positional deviation is calculated based on the rotation angle between the interference pattern obtained when the detection direction is y-direction and the reference pattern. for: ; in, The grating period corresponding to the second grating of the silicon wafer alignment mark. The rotation angle of the interference pattern relative to the reference pattern is the magnitude of the rotation angle. denoted as the topological load number.

[0015] The beneficial effects of this invention are: This invention provides a vortex light interferometric alignment measurement system and detection method based on grating secondary diffraction. The system uses a phase grating as a silicon wafer alignment mark and performs secondary diffraction of vortex light to achieve high-precision detection of the position of the silicon wafer alignment mark. The position detection resolution can reach 0.2nm. By setting multiple optical polarization elements in the system optical path, stray light can be effectively isolated, improving the system's signal-to-noise ratio. Furthermore, the system optical path structure is simple, various optical devices are easy to assemble and adjust, and the system does not have high requirements for the processing precision of each optical element, making it easier to implement. Attached Figure Description

[0016] Figure 1 This is a schematic diagram of the optical path of the alignment measurement system for detecting the x-direction position of a silicon wafer, based on a vortex optical interferometry alignment measurement system with grating secondary diffraction provided in this embodiment.

[0017] Figure 2 This is a schematic diagram of the optical path of the alignment measurement system for detecting the position of a silicon wafer in the y-direction using a vortex optical interferometry alignment measurement system based on grating secondary diffraction provided in this embodiment.

[0018] Figure 3This is a schematic diagram of the silicon wafer alignment mark structure of the vortex optical interferometry alignment measurement system based on grating secondary diffraction provided in this embodiment.

[0019] Figure 4 The reference pattern formed by the grating in its initial position when the topological charge of the vortex interferometric alignment measurement system based on grating secondary diffraction provided in this embodiment is equal to +2 and -2 respectively. Figure 4 In (A), the interference pattern formed after the grating position is shifted by 250nm ( Figure 4 (B) of the diagram shows the interference pattern formed after the grating position is shifted by -150nm. Figure 4 (C) in the middle.

[0020] Reference numerals in the attached figures: 1. Alignment light source; 2. Polarizer; 3. Polarization beam splitter; 4. Silicon wafer; 41. Silicon wafer alignment mark; 41a. First grating; 41b. Second grating; 51. First vortex phase plate; 52. Second vortex phase plate; 53. Third vortex phase plate; 54. Fourth vortex phase plate; 61. First quarter-wave plate; 62. Second quarter-wave plate; 63. Third quarter-wave plate; 64. Fourth quarter-wave plate; 71. First mirror; 72. Second mirror; 73. Third mirror; 74. Fourth mirror; 8. Beam expander; 81. First lens; 82. Second lens; 9. Detector. Detailed Implementation

[0021] In the global coordinate system of the projection lithography machine, x and y represent the horizontal and vertical directions of the horizontal plane, and the z-axis is perpendicular to the xy plane.

[0022] like Figure 1 , Figure 3 As shown, in this embodiment, when detecting the x-direction position of the silicon wafer alignment mark 41, the incident light emitted by the alignment light source 1 along the x-direction passes through the polarizer 2 and exits as a beam with a polarization direction perpendicular to the xz plane. After being reflected by the polarization beam splitter 3, it vertically illuminates the first grating 41a of the silicon wafer alignment mark 41 and diffracts to generate first diffracted light in the x-direction, which is divided into first positive first-order diffracted light and first negative first-order diffracted light.

[0023] The first positive first-order diffracted light passes sequentially through the first vortex phase plate 51 and the first quarter-wave plate 61, and is reflected by the first reflecting mirror 71. It returns along the same path, passes through the first quarter-wave plate 61 and the first vortex phase plate 51 again, and then illuminates the first grating 41a of the silicon wafer alignment mark 41 to undergo diffraction. The generated second positive first-order diffracted light propagates vertically upward, is transmitted through the polarization beam splitter 3, and then passes through the first lens 81 and the second lens 82 of the beam expander 8 before reaching the detector 9.

[0024] The first negative first-order diffracted light passes sequentially through the second vortex phase plate 52 and the second quarter-wave plate 62, and is reflected by the second mirror 72. It returns along the same path, passes through the second quarter-wave plate 62 and the second vortex phase plate 52 again, and then illuminates the first grating 41a of the silicon wafer alignment mark 41 to undergo diffraction. The generated second negative first-order diffracted light propagates vertically upward, is transmitted through the polarization beam splitter 3, and then passes through the first lens 81 and the second lens 82 of the beam expander 8 before reaching the detector 9.

[0025] The second positive first-order diffracted light and the second negative first-order diffracted light are secondary diffracted light. They interfere at detector 9 to form a first interference pattern. The reference pattern is the interference pattern detected on the detection surface of detector 9 when the position offset of the silicon wafer alignment mark 41 is 0. The first interference pattern is determined by the rotation angle of the first interference pattern relative to the reference pattern. Calculate the position offset of the first grating 41a on silicon wafer 4. for: ; in, The grating period corresponding to the first grating 41a of the silicon wafer alignment mark 41. Let be the rotation angle of the interference pattern relative to the reference pattern. denoted as the topological load number.

[0026] like Figure 1 , Figure 2 and Figure 3 As shown, in this embodiment, when detecting the position of the silicon wafer alignment mark 41 in the y direction, the incident light emitted by the alignment light source 1 along the x direction passes through the polarizer 2 and then exits as a beam with a polarization direction perpendicular to the xz plane. After being reflected by the polarization beam splitter 3, it perpendicularly illuminates the second grating 41b of the silicon wafer alignment mark 41 and diffracts to generate first diffracted light in the y direction. This first diffracted light is divided into a third positive first-order diffracted light and a third negative first-order diffracted light.

[0027] The third positive first-order diffracted light passes sequentially through the third vortex phase plate 53 and the third quarter-wave plate 63, and is reflected by the third mirror 73. It returns along the same path, passes through the third quarter-wave plate 63 and the third vortex phase plate 53 again, and then illuminates the second grating 41b of the silicon wafer alignment mark 41 to undergo diffraction. The generated fourth positive first-order diffracted light propagates vertically upward, is transmitted through the polarization beam splitter 3, and then passes through the first lens 81 and the second lens 82 of the beam expander 8 before reaching the detector 9.

[0028] The third negative first-order diffracted light passes sequentially through the fourth vortex phase plate 54 and the fourth quarter-wave plate 64, and is reflected by the fourth reflecting mirror 74. It returns along the same path, passes through the fourth quarter-wave plate 64 and the fourth vortex phase plate 54 again, and then illuminates the second grating 41b of the silicon wafer alignment mark 41 to undergo diffraction. The generated fourth negative first-order diffracted light propagates vertically upward, is transmitted through the polarization beam splitter 3, and then passes through the first lens 81 and the second lens 82 of the beam expander 8 before reaching the detector 9.

[0029] The fourth positive first-order diffracted light and the fourth negative first-order diffracted light are secondary diffracted lights. They interfere at detector 9 to form a second interference pattern. The reference pattern is the interference pattern detected on the detection surface of detector 9 when the position offset of the silicon wafer alignment mark 41 is 0. The second interference pattern is determined by the rotation angle of the second interference pattern relative to the reference pattern. Calculate the position offset of the first grating 41b on silicon wafer 4. for: ; in, The grating period corresponding to the second grating 41b of the silicon wafer alignment mark 41. The rotation angle of the interference pattern relative to the reference pattern is the magnitude of the rotation angle. denoted as the topological load number.

[0030] like Figure 3 As shown, this embodiment provides a schematic diagram of the silicon wafer alignment mark structure of a vortex optical interferometry alignment measurement system based on grating secondary diffraction.

[0031] The silicon alignment mark 41 of silicon wafer 4 is a reflective phase grating. The silicon alignment mark 41 is composed of a first grating 41a and a second grating 41b, both with a grating period of P. The first grating 41a is used for position detection of the silicon alignment mark 41 in the x-direction, and the second grating 41b is used for position detection of the silicon alignment mark 41 in the y-direction. The scribe line direction of the first grating 41a is along the y-direction, and the scribe line direction of the second grating 41b is along the x-direction.

[0032] This embodiment uses the detection direction as the x-direction to demonstrate the effectiveness of calculating the position deviation of the silicon wafer alignment mark in this invention.

[0033] The incident light emitted from the alignment light source 1 along the x-direction passes through the polarizer 2 and exits as a beam with a polarization direction perpendicular to the xz plane. After being reflected by the polarization beam splitter 3, it perpendicularly illuminates the first grating 41a of the alignment mark 41 on the silicon wafer and is diffracted to generate first-order diffracted light in the x-direction. This first-order diffracted light is divided into first positive first-order diffracted light. With the first negative first order diffraction light Propagate upwards. Among them... and Complex amplitudes are respectively ; ; Where A0 represents the amplitude of the positive and negative first-order diffracted light. j It is an imaginary number. Let be the initial phase of beam a. The position of the silicon wafer alignment mark 41 in the x-direction. P The grating period corresponding to the first grating 41a of the silicon wafer alignment mark 41.

[0034] The first positive first-order diffracted light propagates upwards, passes sequentially through the first vortex phase plate 51 and the first quarter-wave plate 61, is reflected by the first reflecting mirror 71, returns along the same path, and passes through the first quarter-wave plate 61 and the first vortex phase plate 51 again, whereby the first positive first-order diffracted light is modulated into a vortex beam. ,in, The complex amplitude is: ; in, The azimuth angle is perpendicular to the plane of beam propagation.

[0035] Vortex beam After diffraction again using the alignment mark, the second positive first-order diffracted light is obtained. The beam, propagating vertically upwards, is transmitted through polarization beam splitter 3, then passes through the first lens 81 and the second lens 82 of beam expander 8 before reaching detector 9. The complex amplitude is: ; The first negative first-order diffracted light propagates upwards, passes sequentially through the second vortex phase plate 52 and the second quarter-wave plate 62, and is reflected by the second mirror 72. Returning along the same path, it passes again through the second quarter-wave plate 62 and the second vortex phase plate 52, and is then modulated into a vortex beam. ,in, The complex amplitude is: ; in, The azimuth angle is perpendicular to the plane of beam propagation.

[0036] Vortex beam After diffraction again using the alignment mark, the second negative first-order diffracted light is obtained. The beam, propagating vertically upwards, is transmitted through polarization beam splitter 3, then passes through the first lens 81 and the second lens 82 of beam expander 8 before reaching detector 9. The complex amplitude is: ; At detector 9, the diffracted light and When interference occurs, the intensity of the interfering light can be expressed as: ; It can be seen that before the two signal lights of detector 9 interfere, they diffract twice at the first grating 41a of silicon wafer alignment mark 41. Therefore, the phase change caused by the position offset of silicon wafer alignment mark is also doubled, which effectively improves the system's sensitivity to position offset measurement.

[0037] like Figure 4 As shown, the reference pattern formed by the grating in its initial position when the topological charge of the vortex beams based on grating secondary diffraction in this embodiment is equal to +2 and -2, respectively, is obtained. Figure 4 The interference pattern formed by (A) and the grating position shifted by 250nm ( Figure 4 (B) and the interference pattern formed after the grating position is shifted by -150nm. Figure 4 In (C), the beam expansion ratio of the beam expander 8 is 1.

[0038] When the silicon wafer moves to align with the first grating 41a of mark 41, the interference pattern rotates by an angle. Displacement of alignment mark 41 with silicon wafer The relationship is: ; The positional offset of the first grating 41a of the silicon wafer alignment mark 41 can be obtained by calculating the rotation angle of the interference pattern. : ; When the graphic rotation angle is When the reference pattern formed at the initial position coincides with the current pattern, it becomes impossible to distinguish changes in the interference pattern, thus limiting the system's displacement measurement range. .

[0039] The specific calculation process for the detection direction in this embodiment is the x-direction: A helium-neon laser LGK7665-18 from Lubang Company was used as the alignment light source 1, emitting a beam with a wavelength of 632.8nm to illuminate the alignment mark 41 on the silicon wafer. The alignment mark 41 on the silicon wafer is periodically... PThe beam expander consists of 2μm gratings. The first lens 81 has a focal length of -25mm and the second lens 82 has a focal length of 50mm, with a beam expansion ratio of 2. The topological charges of the first vortex phase plate 61 and the second vortex phase plate 62 are +1 and -1, respectively. The detector 8 is a Hikvision MV-CU200-20GM with a pixel size of 1.4μm × 1.4μm and a resolution of 5120 × 3840.

[0040] After the light beam with a wavelength of 632.8 nm emitted from the alignment light source 1 illuminates the first grating 41a of the silicon wafer alignment mark 41, the resulting positive and negative first-order diffracted beams return along their respective optical paths after passing through the optical elements in their respective optical paths, and undergo diffraction again on the first grating 41a of the silicon wafer alignment mark 41. Finally, interference occurs at the detector 9, and the intensity of the resulting interference light is expressed as: ; in, The position of the silicon wafer alignment mark 41 in the x-direction. The azimuth angle is perpendicular to the plane of beam propagation. P The grating period corresponding to the first grating 41a of the silicon wafer alignment mark 41.

[0041] When the silicon wafer moves to align with the first grating 41a of mark 41, the interference pattern rotates by an angle. Displacement of the first grating 41a The relationship is: ; The displacement of the first grating 41a can be obtained by detecting the rotation angle of the interference pattern. for: ; The minimum rotation angle of the interference pattern detectable by the detector's detection surface determines the detection accuracy of the silicon wafer alignment mark position, i.e., the system's detection resolution. Based on the parameters of the experimental equipment used, the minimum rotation angle of the interference pattern detectable by the detector's detection surface... The position detection resolution of the system is 0.2 nm, which is 0.057°. When the position offset of the silicon wafer alignment mark is 1 nm, the resulting rotation angle of the interference pattern is 0.18°.

[0042] When the period of the silicon wafer alignment mark in the alignment sensing system is reduced, the pixel size of the detector used is further reduced, and the beam expansion ratio of the beam expander is further increased, the minimum displacement of the silicon wafer alignment mark that the alignment sensing system can detect can be further reduced. However, the processing accuracy of the phase grating, the processing accuracy of the vortex phase plate, and the calculation method of the rotation angle of the interference pattern will all affect the detection accuracy of the silicon wafer alignment mark.

[0043] The specific embodiments described above only illustrate the design principles of the present invention. The shapes and names of the components in this description may differ and are not limited. Therefore, those skilled in the art can modify or make equivalent substitutions to the technical solutions described in the foregoing embodiments; and such modifications and substitutions do not depart from the inventive spirit and technical solutions of the present invention, and should all fall within the protection scope of the present invention.

Claims

1. A vortex optical interferometry alignment measurement system based on grating secondary diffraction, employing a phase grating as a silicon wafer alignment mark, wherein the silicon wafer alignment mark comprises a first grating and a second grating with the same grating period, characterized in that, The vortex optical interferometry alignment measurement system includes: A polarization beam splitter is located directly above the silicon wafer alignment mark; The incident light path includes an alignment light source and a polarizer. The incident light emitted from the alignment light source passes through the polarizer and exits as a beam parallel to the plane where the alignment mark on the silicon wafer is located. After being reflected by the polarizing beam splitter, it is perpendicularly irradiated to the alignment mark on the silicon wafer and diffracted to generate primary diffracted light. The primary diffracted light is divided into positive first-order diffracted light and negative first-order diffracted light in the x-direction and positive first-order diffracted light and negative first-order diffracted light in the y-direction according to the detection direction. The secondary diffraction optical path is divided into a positive first-order secondary diffraction optical path and a negative first-order secondary diffraction optical path in the x-direction and a positive first-order secondary diffraction optical path and a negative first-order secondary diffraction optical path in the y-direction, according to the detection direction. Each secondary diffraction optical path is equipped with a vortex phase plate, a quarter-wave plate and a reflector. In the same detection direction, the primary diffracted light passes through the vortex phase plate and the quarter-wave plate in sequence, is reflected by the reflector, passes through the quarter-wave plate and the vortex phase plate again and is incident on the alignment mark of the silicon wafer and diffracted to generate secondary diffracted light. The detection optical path includes a detector. After the secondary diffracted beams are combined, they pass through the polarization beam splitter and are received by the detector, where they interfere to form an interference pattern.

2. The vortex optical interferometry alignment and measurement system according to claim 1, characterized in that, The silicon wafer alignment marks consist of a reflective phase grating.

3. The vortex optical interferometry alignment and measurement system according to claim 1, characterized in that, The first grating is used for detecting the position of the silicon wafer alignment mark in the x-direction, with the scribe line direction along the y-direction; the second grating is used for detecting the position of the silicon wafer alignment mark in the y-direction, with the scribe line direction along the x-direction. In the global coordinate system of the projection lithography machine, x and y represent the horizontal and vertical directions of the horizontal plane, and the z-axis is perpendicular to the xy plane.

4. The vortex optical interferometry alignment and measurement system according to claim 1, characterized in that, The detection optical path includes a beam expander located above the detector.

5. The vortex optical interferometry alignment and measurement system according to claim 4, characterized in that, The beam expander includes a first lens and a second lens, the distance between the first lens and the second lens is the sum of the focal lengths of the two lenses, and the magnification of the beam expander is the ratio of the focal lengths of the first lens and the second lens.

6. A detection method using the vortex optical interferometry alignment measurement system according to any one of claims 1-5, characterized in that, Includes the following steps: S1. Determine the detection direction of the silicon wafer alignment mark. According to the detection direction, the incident light emitted by the alignment light source passes through the polarizer and exits as a beam parallel to the plane where the silicon wafer alignment mark is located. After being reflected by the polarization beam splitter, it is perpendicularly irradiated to the silicon wafer alignment mark and diffracted to generate first-order diffracted light. The first-order diffracted light is divided into positive first-order diffracted light and negative first-order diffracted light in the detection direction. The first-order diffracted light passes through the vortex phase plate and the quarter-wave plate in sequence, and is reflected by the mirror. It then passes through the quarter-wave plate and the vortex phase plate again and is incident on the silicon wafer alignment mark and diffracted to generate second-order diffracted light. The beams of the second-order diffracted light are combined and pass through the polarization beam splitter. The beams are received by the detector and interfere to form an interference pattern. S2. Calculate the rotation angle between the interference pattern and the reference pattern; The reference pattern is the interference pattern detected on the detector surface when the offset of the silicon wafer alignment mark position is 0, which is obtained in advance. S3. Calculate the position offset of the silicon wafer alignment mark based on the rotation angle between the interference pattern and the reference pattern.

7. The detection method of the vortex optical interferometry alignment measurement system according to claim 6, characterized in that, The detection directions of the silicon wafer alignment mark are divided into the x-direction and the y-direction.

8. The detection method of the vortex optical interferometry alignment measurement system according to claim 7, characterized in that, When the detection direction of the silicon wafer alignment mark is the x-direction, the incident light emitted by the alignment light source along the x-direction passes through the polarizer and exits as a beam with a polarization direction perpendicular to the xz plane. After being reflected by the polarization beam splitter, it vertically illuminates the first grating of the silicon wafer alignment mark and diffracts to generate positive first-order diffracted light and negative first-order diffracted light in the x-direction. Calculate the position deviation in the x-direction for: ； in, The grating period corresponding to the first grating of the silicon wafer alignment mark. Let be the rotation angle of the interference pattern relative to the reference pattern. denoted as the topological load number.

9. The detection method of the vortex optical interferometry alignment measurement system according to claim 7, characterized in that, When the detection direction of the silicon wafer alignment mark is the y direction, the incident light emitted by the alignment light source along the x direction passes through the polarizer and exits as a beam with a polarization direction perpendicular to the xz plane. After being reflected by the polarization beam splitter, it vertically illuminates the second grating of the silicon wafer alignment mark and diffracts to generate positive first-order diffracted light and negative first-order diffracted light in the y direction. Calculate the position deviation in the y-direction for: ； in, The grating period corresponding to the second grating of the silicon wafer alignment mark. The rotation angle of the interference pattern relative to the reference pattern is the magnitude of the rotation angle. denoted as the topological load number.

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