Grating diffracted beam interferometric off-axis alignment measurement device

Abstract

This invention relates to an off-axis alignment measurement device for grating diffraction beam interference between a silicon wafer and a workpiece stage, belonging to the field of photolithography technology. The invention employs a four-channel beam combiner to combine four different wavelength laser beams. A beam control module processes the beam output from the four-channel beam combiner. A self-referenced interferometer mirror group generates multi-order aliasing diffraction signals from the grating. A normalized signal detection module acquires the multi-order alignment signals. Finally, a software module analyzes and processes the acquired alignment signals, improving the system's process adaptability. This invention, combining a beam control module, two sets of self-referenced interferometer mirrors, and a normalized signal detection module, solves the problem of laser beam polarization state, intensity fluctuations, and stray beams within the system affecting the alignment signal quality, thereby improving the system's signal detection accuracy and stability.

Description

Technical Field

[0001] This invention belongs to the field of photolithography technology, and mainly relates to a grating diffraction beam interference off-axis alignment measurement device for photolithography systems. Background Technology

[0002] As the core of the next-generation information technology industry, the integrated circuit (IC) chip manufacturing process is extremely complex and requires stringent process control. It mainly includes multiple processes such as photoresist coating, photolithography exposure, development, etching, ion doping, resist removal, and deposition. The key challenge in IC chip manufacturing lies in transferring the circuit pattern from the photomask onto the photosensitive material of the silicon substrate. This process requires photolithography exposure. IC chip fabrication typically involves 25-40 repeated overlay exposures. Before each circuit pattern layer is exposed, the corresponding photomask needs to establish an accurate relative position with the circuit pattern from the previous photolithography exposure, while simultaneously ensuring the relative positional accuracy of each layer with the layers before and after it. Therefore, the photolithography system requires alignment and measurement devices to achieve high-precision alignment between the mask and the silicon wafer.

[0003] The alignment measurement methods in mainstream lithography systems are mainly coaxial alignment and off-axis alignment. Coaxial alignment involves aligning the mask and workpiece stage before overlay exposure, measuring the coordinates of both the mask and the workpiece stage in the machine coordinate system, and calculating the positional relationship between the mask and the stage. Off-axis alignment involves aligning the silicon wafer and the workpiece stage before overlay exposure, measuring both coordinates and calculating the positional relationship between the wafer and the stage. By comparing the positions of the mask and wafer relative to the stage, the relative positional relationship between them is obtained to meet overlay accuracy requirements. Currently, the off-axis alignment measurement devices used in mainstream lithography systems are based on the principle of grating diffraction beam interference. This involves using a grating mark as a measurement reference and extracting the phase difference of the interference alignment signal from the multi-order diffraction beams of the grating mark to calculate the positional information of the grating mark. Because the grating marks are etched onto the silicon wafer surface, and the wafer undergoes processes such as chemical mechanical polishing, coating, and oxidation, the grating marks undergo asymmetric deformation. This weakens the detection signal and introduces an additional phase difference, leading to significant deviations in the calculated position information. Ultimately, this affects the performance of the alignment measurement device and reduces its process adaptability. Secondly, since the size of the grating marks is close to the wavelength of the illumination beam, factors such as the laser beam polarization state, intensity fluctuations, and stray beams within the system greatly influence the phase measurement accuracy of the alignment signal, ultimately resulting in a decrease in the device's alignment accuracy.

[0004] Therefore, the technical problem that urgently needs to be solved by those skilled in the art is: when the size of the grating mark is continuously reduced to the order of the wavelength of the illumination beam, and after the grating mark has undergone chemical mechanical polishing, coating and oxidation processes, how can we ensure that the system generates a sufficiently high signal intensity, and effectively suppress the influence of factors such as the polarization state of the laser beam, light intensity fluctuations and stray beams inside the system on the alignment signal quality. Summary of the Invention

[0005] The purpose of this invention is to overcome the shortcomings of existing technologies and propose a grating diffraction beam interferometry off-axis alignment measurement device. This invention utilizes a four-channel beam combiner to combine four different wavelength laser beams to illuminate the grating mark, thereby improving the system's process adaptability. Furthermore, the system incorporates a beam control module, two sets of self-reference interferometer mirrors, and a normalized signal detection module to suppress the influence of laser beam polarization state, intensity fluctuations, and stray beams within the system on the alignment signal quality. This invention overcomes the challenges of low process adaptability and significant internal interference noise in traditional grating diffraction beam interferometry alignment measurement systems.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] This invention proposes a grating diffraction beam interferometry off-axis alignment measurement device, characterized in that the device comprises: a light source module, a beam control module, a signal generation module, a first self-reference interferometer mirror group module, a first normalized signal detection module, a second self-reference interferometer mirror group module, a second normalized signal detection module, and a software module; wherein:

[0008] In the light source module, a four-channel beam combiner is used to combine the lasers emitted by the first, second, third, and fourth lasers and guide them to the beam control module.

[0009] In the beam control module, an optical modulator modulates the laser beam output from the light source module, an optical polarization controller changes the polarization state of the beam output from the optical modulator, an optical collimator collimates the beam output from the optical polarization controller, and guides it to the signal generation module.

[0010] In the signal generation module, the laser beam output from the beam control module is sequentially passed through a micro-reflector and a focusing lens to converge onto the surface of the measurement grating mark. A large numerical aperture focusing lens is used to collect the diffracted beam generated by the surface of the measurement grating mark. A spatial filter is used to filter the collected diffracted beam. Then, the first polarization beam splitter is used to split the filtered beam into two paths, which are then guided to the first self-reference interferometer module and the second self-reference interferometer module, respectively.

[0011] In the first self-reference interferometer module, the beam passing through the first half-wave plate is split into two paths by the second polarization beam splitter. One beam passes through the first quarter-wave plate and the first mirror in sequence, while the other beam passes through the second quarter-wave plate and the first prism in sequence to achieve optical field reversal. The two beams are then combined by the second polarization beam splitter. The combined beam is formed by the superposition of two beams with mutually orthogonal polarization states and wavefronts that are 180° rotationally symmetrical to each other, and enters the first normalized signal detection module.

[0012] In the first normalized signal detection module, the beam passing through the second half-wave plate is split into two paths using the third polarization beam splitter. One path is split into beam measurement signals corresponding to four wavelengths by the first beam splitting system, and the other path is split into beam reference signals corresponding to four wavelengths by the second beam splitting system. The first multi-channel photodetector and the second multi-channel photodetector (506) are then used for synchronous detection, and the detection signals are transmitted to the software module.

[0013] In the second self-reference interferometer module, the beam passing through the third half-wave plate is split into two paths by the fourth polarization beam splitter. One beam passes through the third quarter-wave plate and the second mirror in sequence, while the other beam passes through the fourth quarter-wave plate and the second prism in sequence to achieve the flipping of the light field. The two beams are then combined by the fourth polarization beam splitter and enter the second normalized signal detection module.

[0014] In the second normalized signal detection module, the beam passing through the fourth half-wave plate is split into two paths using the fifth polarization beam splitter. One path is split into beam measurement signals corresponding to four wavelengths by the fourth beam splitting system, and the other path is split into beam reference signals corresponding to four wavelengths by the third beam splitting system. Then, the fourth multi-channel photodetector and the third multi-channel photodetector are used for synchronous detection, and the detection signals are transmitted to the software module.

[0015] In the software module, the beam measurement signals and beam reference signals corresponding to the four wavelengths transmitted by the first normalized signal detection module and the second normalized signal detection module are normalized respectively. The alignment signal intensity of each wavelength is the ratio of the beam measurement signal intensity of the corresponding wavelength to the sum of the beam measurement signal intensity and the beam reference signal intensity.

[0016] Furthermore, the first, second, third, and fourth lasers can be solid-state lasers or semiconductor lasers, or a combined system of solid-state lasers and semiconductor lasers, and the laser beams emitted from the four wavelengths corresponding to the four-channel beam combiner have the same polarization state.

[0017] Furthermore, the optical modulator can be an amplitude modulator or a phase modulator, or a combined system of amplitude modulator and phase modulator, and the optical polarization controller changes the polarization state of the beam output by the optical modulator to a circular polarization state.

[0018] Furthermore, the focusing lens can be a single lens or a lens group composed of multiple lenses of different types. The measurement grating mark is located on the object-side focal plane of the focusing lens, and the function of the spatial filter is to filter the diffracted beam generated by the surface of the measurement grating mark, allowing only specific order diffracted beams to pass through. It can be a spatial light modulator or a slit array composed of multiple adjustable slits.

[0019] Furthermore, the first prism can be a right-angle prism or a Dove prism. The two beams split by the second polarization beam splitter have the same optical path. After being combined by the second polarization beam splitter, the complementary superposition of the light fields of the two beams can be achieved, thereby forming a multi-order aliasing diffraction signal.

[0020] Furthermore, the function of the first and second beam splitting systems is to decompose the two beams generated by the third polarizing beam splitter into beam signals corresponding to four wavelengths. These systems can be composed of multiple dichroic mirrors and lenses, multiple filters and lenses, or a combined system of multiple dichroic mirrors, filters and lenses, with the optical plane centers of all optical elements coinciding with the incident optical axis.

[0021] Furthermore, the second prism can be a right-angle prism or a Dove prism. The two beams split by the fourth polarization beam splitter have the same optical path. After being combined by the fourth polarization beam splitter, the complementary superposition of the light fields of the two beams can be achieved, thereby forming a multi-order aliasing diffraction signal.

[0022] Furthermore, the function of the third and fourth beam splitting systems is to decompose the two beams generated by the fifth polarizing beam splitter into beam signals corresponding to four wavelengths. These systems can be composed of multiple dichroic mirrors and lenses, multiple filters and lenses, or a combination of multiple dichroic mirrors, filters and lenses, with the optical plane centers of all optical elements coinciding with the incident optical axis.

[0023] Furthermore, the software module normalizes the beam measurement signals and beam reference signals corresponding to each wavelength under different polarization states to obtain the alignment signals of each wavelength under different polarization states. At the same time, by analyzing the phase information of the alignment signals of each wavelength under different polarization states, the mark position deviation information is calculated.

[0024] The beneficial effects of this invention are that it combines four different wavelength laser beams using a four-channel beam combiner to illuminate the grating mark, thereby improving process adaptability. Furthermore, by introducing a beam control module, two sets of self-reference interferometers, and a normalized signal detection module into the system, the influence of factors such as laser beam polarization state, intensity fluctuations, and stray beams within the system on the alignment signal quality is suppressed, thereby improving the system's signal detection accuracy and stability. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the off-axis alignment measurement device for grating diffraction beam interference according to an embodiment of the present invention.

[0026] The components are: 1-Light source module, 101-First laser, 102-Second laser, 103-Third laser, 104-Fourth laser, 105-Four-channel beam combiner, 2-Beam control module, 201-Optical modulator, 202-Optical polarization controller, 203-Optical collimator, 3-Signal generation module, 301-Micro mirror, 302-Focusing lens, 303-Measurement grating mark, 304-Spatial filter, 305-First polarization beam splitter, 4-First self-reference interferometer module, 401-First half-wave plate, 402-Second polarization beam splitter, 403-First quarter-wave plate, 404-First mirror, 405-Second quarter-wave plate, 406-First prism, 5-First normalized signal detection module, 5 01-Second half-wave plate, 502-Third polarization beam splitter, 503-First beam splitting system, 504-First multi-channel photodetector, 505-Second beam splitting system, 506-Second multi-channel photodetector, 6-Second self-reference interferometer module, 601-Third half-wave plate, 602-Fourth polarization beam splitter, 603-Third quarter-wave plate, 604-Second mirror, 605-Fourth quarter-wave plate, 606-Second prism, 7-Second normalized signal detection module, 701-Fourth half-wave plate, 702-Fifth polarization beam splitter, 703-Third beam splitting system, 704-Third multi-channel photodetector, 705-Fourth beam splitting system, 706-Fourth multi-channel photodetector, 8-Software module. Detailed Implementation

[0027] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0028] A schematic diagram of an off-axis alignment measurement device for grating diffraction beam interference according to an embodiment of the present invention is shown below. Figure 1As shown. The device includes a light source module (1), a beam control module (2), a signal generation module (3), a first self-reference interferometer mirror group module (4), a first normalized signal detection module (5), a second self-reference interferometer mirror group module (6), a second normalized signal detection module (7), and a software module (8).

[0029] In the light source module (1): the first laser (101), the second laser (102), the third laser (103) and the fourth laser (104) output four different wavelengths of linearly polarized laser beams. The laser beams output by the first laser (101), the second laser (102), the third laser (103) and the fourth laser (104) are combined using a four-channel beam combiner (105) and guided to the beam control module (2) through an optical fiber.

[0030] In the beam control module (2): by setting the modulation parameters of the optical modulator (201), the amplitude or phase of the laser beam output by the four-channel beam combiner (105) is modulated. The modulated laser beam is guided by the optical fiber to the optical polarization controller (202). The optical polarization controller (202) changes the linear polarization state of the beam output by the optical modulator (201) to the circular polarization state. Then, the optical collimator (203) collimates the beam output by the optical polarization controller (202) and guides it to the surface of the micro-mirror (301).

[0031] In the signal generation module (3): the circularly polarized light output from the optical collimator (203) is reflected by the micro-mirror (301) to the focusing lens (302) and converged to the surface of the measurement grating mark (303). The focusing lens (302) with a large numerical aperture collects the multi-order diffraction beam generated by the surface of the measurement grating mark (303). The collected diffraction beam is filtered by the spatial filter (304) to allow only specific order diffraction beams to pass through. Then, the first polarization beam splitter (305) splits the filtered circularly polarized light into two paths of S-polarized light and P-polarized light, and guides them to the first self-reference interferometer module (4) and the second self-reference interferometer module (6), respectively.

[0032] In the first self-reference interferometer module (4): the polarization direction of the S-linearly polarized light generated by the first polarization beam splitter (305) is changed by 45° using the first half-wave plate (401). The second polarization beam splitter (402) splits the linearly polarized light passing through the first half-wave plate (401) into two paths. One beam passes through the first quarter-wave plate (403) and the first reflector (404) in sequence, and the other beam passes through the second quarter-wave plate (405) and the first prism (406) in sequence to achieve the reversal of the light field. The second polarization beam splitter (402) then combines the two beams. The combined beam is formed by the superposition of two beams whose polarization states are orthogonal to each other and whose wavefronts are 180° rotationally symmetrical. The combined beam then enters the first normalized signal detection module (5).

[0033] In the first normalized signal detection module (5): the polarization direction of the two linearly polarized beams emitted from the second polarization beam splitter (402) is changed by 45° using the second half-wave plate (501). The beam transmitted through the second half-wave plate (501) is split into two paths using the third polarization beam splitter (502). One path is split into four wavelength-corresponding beam measurement signals by the first beam splitting system (503), and the other path is split into four wavelength-corresponding beam reference signals by the second beam splitting system (505). The first multi-channel photodetector (504) and the second multi-channel photodetector (506) are used for synchronous detection, and the detection signals are transmitted to the software module (8).

[0034] In the second self-reference interferometer module (6): the polarization direction of the P-linearly polarized light generated by the first polarization beam splitter (305) is changed by 45° using the third half-wave plate (601). The linearly polarized light passing through the third half-wave plate (601) is split into two paths using the fourth polarization beam splitter (602). One beam passes through the third quarter-wave plate (603) and the second mirror (604) in sequence, and the other beam passes through the fourth quarter-wave plate (605) and the second prism (606) in sequence to achieve the reversal of the light field. The two beams are then combined by the fourth polarization beam splitter (602). The combined beam is formed by the superposition of two beams whose polarization states are orthogonal to each other and whose wavefronts are 180° rotationally symmetrical. The beam then enters the second normalized signal detection module (7).

[0035] In the second normalized signal detection module (7): the polarization direction of the two linearly polarized beams emitted from the fourth polarization beam splitter (602) is changed by 45° using the fourth half-wave plate (701). The beam transmitted through the fourth half-wave plate (701) is split into two paths using the fifth polarization beam splitter (702). One path is split into four wavelength-corresponding beam measurement signals by the third beam splitting system (703), and the other path is split into four wavelength-corresponding beam reference signals by the fourth beam splitting system (705). Then, the third multi-channel photodetector (704) and the fourth multi-channel photodetector (706) are used for synchronous detection, and the detection signals are transmitted to the software module (8).

[0036] In software module (8): the data acquisition and processing system is used to normalize the beam measurement signals and beam reference signals corresponding to the four wavelengths transmitted by the first normalized signal detection module (5) and the second normalized signal detection module (7) under different polarization states, so as to obtain the alignment signals of each wavelength under different polarization states. The alignment signal intensity of each wavelength under different polarization states is the ratio of the beam measurement signal intensity of the corresponding wavelength to the sum of the beam measurement signal intensity and the beam reference signal intensity. By analyzing the phase information of the alignment signal of each wavelength under different polarization states, the mark position deviation information is calculated.

[0037] The foregoing has provided a detailed description of the grating diffraction beam interference off-axis alignment measurement device proposed in this invention. This document elucidates the principle and implementation methods of this invention. The descriptions of the embodiments above are merely for the purpose of helping to understand the core idea of ​​this invention. Furthermore, those skilled in the art will recognize that, based on the concept of this invention, there will be changes in specific implementation methods and application scope. These changes should all fall within the protection scope of the appended claims. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A grating diffraction beam interference off-axis alignment measurement device, characterized in that... The device includes: a light source module (1), a beam control module (2), a signal generation module (3), a first self-reference interferometer mirror group module (4), a first normalized signal detection module (5), a second self-reference interferometer mirror group module (6), a second normalized signal detection module (7), and a software module (8). The light source module (1) includes a first laser (101), a second laser (102), a third laser (103), a fourth laser (104), and a four-channel beam combiner (105). The four-channel beam combiner (105) combines the lasers emitted by the first laser (101), the second laser (102), the third laser (103), and the fourth laser (104) and guides them to the beam control module (2). The beam control module (2) includes an optical modulator (201), an optical polarization controller (202), and an optical collimator (203). The optical modulator (201) modulates the laser beam output from the light source module (1), the optical polarization controller (202) changes the polarization state of the beam output from the optical modulator (201), and the optical collimator (203) collimates the beam output from the optical polarization controller (202) and guides it to the signal generation module (3). The signal generation module (3) includes a micro-mirror (301), a focusing lens (302), a measurement grating mark (303), a spatial filter (304), and a first polarization beam splitter (305). The laser beam output by the beam control module (2) passes through the micro-mirror (301) and the focusing lens (302) in sequence and is focused onto the surface of the measurement grating mark (303). The focusing lens (302) with a large numerical aperture collects the diffracted beam generated by the surface of the measurement grating mark (303). The spatial filter (304) filters the collected diffracted beam. The first polarization beam splitter (305) splits the filtered beam into two paths and guides them to the first self-reference interferometer module (4) and the second self-reference interferometer module (6), respectively. The first self-reference interferometer module (4) includes a first half-wave plate (401), a second polarization beam splitter (402), a first quarter-wave plate (403), a first reflector (404), a second quarter-wave plate (405), and a first prism (406). The second polarization beam splitter (402) splits the light beam passing through the first half-wave plate (401) into two paths. One path passes through the first quarter-wave plate (403) and the first reflector (404) in sequence, while the other path passes through the second quarter-wave plate (405) and the first prism (406) in sequence to achieve the flipping of the light field. The second polarization beam splitter (402) then combines the two beams and enters the first normalized signal detection module (5). The first normalized signal detection module (5) includes a second half-wave plate (501), a third polarization beam splitter (502), a first beam splitting system (503), a first multi-channel photodetector (504), a second beam splitting system (505), and a second multi-channel photodetector (506). The third polarization beam splitter (502) splits the beam passing through the second half-wave plate (501) into two paths. One path is split into beam measurement signals corresponding to four wavelengths by the first beam splitting system (503), and the other path is split into beam reference signals corresponding to four wavelengths by the second beam splitting system (505). The first multi-channel photodetector (504) and the second multi-channel photodetector (506) are then used for synchronous detection, and the detection signals are transmitted to the software module (8). The second self-reference interferometer module (6) includes a third half-wave plate (601), a fourth polarization beam splitter (602), a third quarter-wave plate (603), a second mirror (604), a fourth quarter-wave plate (605), and a second prism (606). The fourth polarization beam splitter (602) splits the light beam passing through the third half-wave plate (601) into two paths. One path passes through the third quarter-wave plate (603) and the second mirror (604) in sequence, while the other path passes through the fourth quarter-wave plate (605) and the second prism (606) in sequence to achieve the flipping of the light field. The fourth polarization beam splitter (602) then combines the two beams and enters the second normalized signal detection module (7). The second normalized signal detection module (7) includes a fourth half-wave plate (701), a fifth polarization beam splitter (702), a third beam splitting system (703), a third multi-channel photodetector (704), a fourth beam splitting system (705), and a fourth multi-channel photodetector (706). The fifth polarization beam splitter (702) splits the beam passing through the fourth half-wave plate (701) into two paths. One path is split into beam measurement signals corresponding to four wavelengths by the fourth beam splitting system (705), and the other path is split into beam reference signals corresponding to four wavelengths by the third beam splitting system (703). The fourth multi-channel photodetector (706) and the third multi-channel photodetector (704) are then used for synchronous detection, and the detection signals are transmitted to the software module (8). The software module (8) includes a data acquisition and processing system, which performs normalization processing on the beam measurement signals and beam reference signals corresponding to the four wavelengths transmitted by the first normalized signal detection module (5) and the second normalized signal detection module (7), respectively. The alignment signal intensity of each wavelength is the ratio of the beam measurement signal intensity of the corresponding wavelength to the sum of the beam measurement signal intensity and the beam reference signal intensity.

2. The grating diffraction beam interference off-axis alignment measuring device according to claim 1, characterized in that... The first laser (101), the second laser (102), the third laser (103), and the fourth laser (104) are solid-state lasers or semiconductor lasers, or a combined system of solid-state lasers and semiconductor lasers, and the laser beams emitted from the four wavelengths corresponding to the four-channel beam combiner (105) have the same polarization state.

3. The grating diffraction beam interference off-axis alignment measuring device according to claim 1, characterized in that... The optical modulator (201) is an amplitude modulator or a phase modulator, or a combination of amplitude modulator and phase modulator. The optical polarization controller (202) changes the polarization state of the beam output by the optical modulator (201) to a circular polarization state.

4. The grating diffraction beam interference off-axis alignment measuring device according to claim 1, characterized in that... The focusing lens (302) is a single lens or a lens group composed of multiple lenses of different types. The measuring grating mark (303) is located on the object-side focal plane of the focusing lens (302), and the spatial filter (304) filters the diffracted beam generated by the surface of the measuring grating mark (303) and only allows specific order diffracted beams to pass through. It is a spatial light modulator or a slit array composed of multiple adjustable slits.

5. The grating diffraction beam interference off-axis alignment measuring device according to claim 1, characterized in that... The first prism (406) is a right-angle prism or a Dove prism. The two beams split by the second polarization beam splitter (402) have the same optical path. After being combined by the second polarization beam splitter (402), the complementary superposition of the light fields of the two beams is realized, thereby forming a multi-level aliasing diffraction signal.

6. The grating diffraction beam interference off-axis alignment measuring device according to claim 1, characterized in that... The function of the first beam splitting system (503) and the second beam splitting system (505) is to decompose the two beams generated by the third polarizing beam splitter (502) into beam signals corresponding to four wavelengths. They are composed of multiple dichroic mirrors and lenses, or multiple filters and lenses, or a combination of multiple dichroic mirrors, filters and lenses, and the optical plane center of all optical elements coincides with the incident optical axis.

7. The grating diffraction beam interference off-axis alignment measuring device according to claim 1, characterized in that... The second prism (606) is a right-angle prism or a Dove prism. The two beams split by the fourth polarization beam splitter (602) have the same optical path. After being combined by the fourth polarization beam splitter (602), the complementary superposition of the light fields of the two beams is realized, thereby forming a multi-level aliasing diffraction signal.

8. The grating diffraction beam interference off-axis alignment measuring device according to claim 1, characterized in that... The function of the third beam splitting system (703) and the fourth beam splitting system (705) is to decompose the two beams generated by the fifth polarization beam splitter (702) into beam signals corresponding to four wavelengths. They are composed of multiple dichroic mirrors and lenses, or multiple filters and lenses, or a combination of multiple dichroic mirrors, filters and lenses, and the optical plane center of all optical elements coincides with the incident optical axis.

9. The grating diffraction beam interference off-axis alignment measuring device according to claim 1, characterized in that... The software module (8) is used to normalize the beam measurement signal and the beam reference signal corresponding to each wavelength under different polarization states to obtain the alignment signal of each wavelength under different polarization states. At the same time, by analyzing the phase information of the alignment signal of each wavelength under different polarization states, the mark position deviation information is calculated.

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