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CN-115981121-B - Grating diffraction light beam interference off-axis alignment measuring device

CN115981121BCN 115981121 BCN115981121 BCN 115981121BCN-115981121-B

Abstract

The invention relates to a grating diffraction beam interference off-axis alignment measuring device used between a silicon wafer and a workpiece table, belonging to the technical field of photoetching; the four-channel beam combiner is used for combining four laser beams with different wavelengths, the beam regulation and control module is used for processing the beams output by the four-channel beam combiner, the self-reference interference lens group is used for generating grating multi-order aliasing diffraction signals, the normalization signal detection module is used for collecting multi-order alignment signals, and finally the software module is used for analyzing and processing the collected alignment signals, so that the process adaptability of the system is improved. The invention combines the beam regulation module, the two self-reference interference lens groups and the normalized signal detection module, solves the problem that factors such as the polarization state of the laser beam, the fluctuation of the light intensity, the scattered light inside the system and the like influence the quality of the alignment signal, thereby improving the signal detection precision and the stability of the system.

Inventors

  • WANG WEIBO
  • HUANG KANGSHENG
  • SONG PEIYU
  • TAN JIUBIN

Assignees

  • 哈尔滨工业大学

Dates

Publication Date
20260505
Application Date
20230301

Claims (9)

  1. 1. The device is characterized by comprising a light source module (1), a light beam regulating and controlling module (2), a signal generating module (3), a first self-reference interference lens group module (4), a first normalization signal detection module (5), a second self-reference interference lens group module (6), a second normalization signal detection module (7) and a software module (8); the light source module (1) comprises a first laser (101), a second laser (102), a third laser (103), a fourth laser (104) and a four-channel beam combiner (105), and laser beams emitted by the first laser (101), the second laser (102), the third laser (103) and the fourth laser (104) are combined by the four-channel beam combiner (105) and guided to the light beam regulating module (2); the light beam regulation and control module (2) comprises a light modulator (201), a light polarization controller (202) and a light collimator (203), the light modulator (201) is used for modulating the laser beam output by the light source module (1), the polarization state of the light beam output by the light modulator (201) is changed by the light polarization controller (202), and the light beam output by the light polarization controller (202) is collimated by the light collimator (203) and guided to the signal generation module (3); the signal generation module (3) comprises a micro-mirror (301), a focusing lens (302), a measuring grating mark (303), a spatial filter (304) and a first polarization beam splitter (305), laser beams output by the beam regulation module (2) are sequentially converged on the surface of the measuring grating mark (303) through the micro-mirror (301) and the focusing lens (302), diffraction beams generated by the surface of the measuring grating mark (303) are collected through the focusing lens (302) with a large numerical aperture, the collected diffraction beams are filtered through the spatial filter (304), and the filtered beams are split into two paths through the first polarization beam splitter (305) and are respectively guided to the first self-reference interference lens group module (4) and the second self-reference interference lens group module (6); The first self-reference interference mirror group module (4) comprises a first half wave plate (401), a second polarization beam splitter (402), a first quarter wave plate (403), a first reflecting mirror (404), a second quarter wave plate (405) and a first prism (406), the second polarization beam splitter (402) is used for dividing the light beam transmitted through the first half wave plate (401) into two paths, one path of light beam sequentially passes through the first quarter wave plate (403) and the first reflecting mirror (404), the other path of light beam sequentially passes through the second quarter wave plate (405) and the first prism (406) to realize the overturn of the light field, and the second polarization beam splitter (402) is used for combining the two paths of light beams to enter the first normalization signal detection module (5); The first normalization signal detection module (5) comprises a second half wave plate (501), a third polarization beam splitter (502), a first beam splitting system (503), a first multi-channel photoelectric detector (504), a second beam splitting system (505) and a second multi-channel photoelectric detector (506), the third polarization beam splitter (502) is used for splitting the light beam transmitted through the second half wave plate (501) into two paths, one path of the light beam is split into light beam measurement signals corresponding to four wavelengths through the first beam splitting system (503), the other path of the light beam is split into light beam reference signals corresponding to four wavelengths through the second beam splitting system (505), the first multi-channel photoelectric detector (504) and the second multi-channel photoelectric detector (506) are used for synchronous detection, and the detection signals are transmitted to the software module (8); The second self-reference interference lens group module (6) comprises a third half wave plate (601), a fourth polarization beam splitter (602), a third quarter wave plate (603), a second reflecting mirror (604), a fourth quarter wave plate (605) and a second prism (606), the fourth polarization beam splitter (602) is used for dividing the light beam transmitted through the third half wave plate (601) into two paths, one path of light beam sequentially passes through the third quarter wave plate (603) and the second reflecting mirror (604), the other path of light beam sequentially passes through the fourth quarter wave plate (605) and the second prism (606) to realize the overturn of the light field, and the fourth polarization beam splitter (602) is used for combining the two paths of light beams to enter the second normalization signal detection module (7); The second normalization signal detection module (7) comprises a fourth half wave plate (701), a fifth polarization beam splitter (702), a third beam splitting system (703), a third multi-channel photoelectric detector (704), a fourth beam splitting system (705) and a fourth multi-channel photoelectric detector (706), the fifth polarization beam splitter (702) is used for splitting the light beam transmitted through the fourth half wave plate (701) into two paths, one path of the light beam is split into light beam measurement signals corresponding to four wavelengths through the fourth beam splitting system (705), the other path of the light beam is split into light beam reference signals corresponding to four wavelengths through the third beam splitting system (703), and then the fourth multi-channel photoelectric detector (706) and the third multi-channel photoelectric detector (704) are used for synchronous detection, and detection signals are transmitted to the software module (8); The software module (8) comprises a data acquisition and processing system, and performs normalization processing on the light beam measurement signals and the light beam reference signals corresponding to the four wavelengths transmitted by the first normalization signal detection module (5) and the second normalization signal detection module (7), wherein the alignment signal intensities of the various wavelengths are the ratio of the light beam measurement signal intensities of the corresponding wavelengths to the sum of the light beam measurement signal intensities and the light beam reference signal intensities.
  2. 2. The device according to claim 1, wherein 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 polarization states of the laser beams emitted from the lasers having four wavelengths corresponding to the four-channel beam combiner (105) are the same.
  3. 3. The device according to claim 1, wherein the light modulator (201) is an amplitude modulator or a phase modulator, or a combination system of an amplitude modulator and a phase modulator, and the light polarization controller (202) changes the polarization state of the light beam output by the light modulator (201) into a circular polarization state.
  4. 4. The grating-diffracted-beam interference off-axis alignment measuring apparatus according to claim 1, characterized in that the focusing lens (302) is a single lens or a lens group composed of a plurality of different types of lenses, the measuring grating mark (303) is located on an object-side focal plane of the focusing lens (302), and the spatial filter (304) functions to filter the diffracted beam generated by the surface of the measuring grating mark (303) to allow only a specific order of diffracted beam to pass, and is a spatial light modulator or a slit array composed of a plurality of adjustable slits.
  5. 5. The grating-diffracted-beam interference off-axis alignment measurement device according to claim 1, wherein the first prism (406) is a right-angle prism or a dove prism, the optical paths of the two light beams split by the second polarizing beam splitter (402) are the same, and after the two light beams are combined by the second polarizing beam splitter (402), complementary superposition of light fields of the two light beams is realized, so as to form a multi-order aliasing diffraction signal.
  6. 6. The grating-diffracted-beam interference off-axis alignment measurement apparatus according to claim 1, wherein the first beam splitting system (503) and the second beam splitting system (505) function to split two paths of light generated by the third polarizing beam splitter (502) into four beam signals corresponding to four wavelengths, respectively, and are composed of a plurality of dichroic mirrors and lenses or a plurality of filters and lenses, or a combination system composed of a plurality of dichroic mirrors, filters and lenses, and the optical plane centers of all optical elements coincide with the incident optical axis.
  7. 7. The grating-diffracted-beam interference off-axis alignment measurement device according to claim 1, wherein the second prism (606) is a right-angle prism or a dove prism, the optical paths of the two light beams split by the fourth polarizing beam splitter (602) are the same, and after the light beams are combined by the fourth polarizing beam splitter (602), complementary superposition of light fields of the two light beams is realized, so that a multi-order aliasing diffraction signal is formed.
  8. 8. The grating-diffracted-beam interference off-axis alignment measurement apparatus according to claim 1, wherein the third beam splitting system (703) and the fourth beam splitting system (705) function to split two paths of light generated by the fifth polarizing beam splitter (702) into four beam signals corresponding to four wavelengths, respectively, are composed of a plurality of dichroic mirrors and lenses or composed of a plurality of filters and lenses, or are combined systems composed of a plurality of dichroic mirrors, filters and lenses, and the optical plane centers of all optical elements coincide with the incident optical axis.
  9. 9. The device for off-axis alignment measurement of grating diffraction beam interferometry according to claim 1, wherein the software module (8) is configured to normalize the beam measurement signals corresponding to each wavelength in different polarization states with the beam reference signal to obtain alignment signals of each wavelength in different polarization states, and calculate the mark position deviation information by analyzing phase information of the alignment signals of each wavelength in different polarization states.

Description

Grating diffraction light beam interference off-axis alignment measuring device Technical Field The invention belongs to the technical field of lithography, and mainly relates to a grating diffraction beam interference off-axis alignment measuring device for a lithography system. Background The integrated circuit industry is the core of the new generation information technology industry, the manufacturing process of the chip is extremely complex, the process flow is extremely demanding, and the integrated circuit industry mainly comprises multiple process flows of photoresist coating, photoetching exposure, development, etching, ion doping, photoresist removal, deposition and the like. In the process of manufacturing integrated circuit chips, the difficulty and key point is that the circuit pattern on the mask is printed on the photosensitive material of the silicon substrate, and the process needs to be realized through photoetching exposure. The fabrication of integrated circuit chips generally requires 25-40 repeated overlay exposures, and before each layer of circuit pattern is exposed, the corresponding mask plate needs to establish an accurate relative positional relationship with the circuit pattern exposed by the previous lithography, and simultaneously ensures the relative positional precision of each layer and the front and back layers of circuit patterns. For this reason, the lithography system is required to be equipped with an alignment measurement device to achieve high precision alignment between the mask and the silicon wafer. The alignment measurement mode of the mainstream photoetching system mainly comprises on-axis alignment and off-axis alignment. The coaxial alignment measurement mode is to realize the alignment between the mask and the workpiece table before the overlay exposure, namely, to measure the coordinates of the mask in a machine coordinate system and the coordinates of the workpiece table in the machine coordinate system, and to calculate the position relation of the mask relative to the workpiece table. The off-axis alignment measurement mode is to realize the alignment between the silicon wafer and the workpiece stage before the overlay exposure, namely, the coordinates of the silicon wafer in a machine coordinate system and the coordinates of the workpiece stage in the machine coordinate system are measured, and the position relation of the silicon wafer relative to the workpiece stage is calculated. And comparing the positions of the mask and the silicon wafer relative to the workpiece table, so as to obtain the relative position relationship between the mask and the silicon wafer, thereby meeting the requirement of overlay accuracy. Currently, an off-axis alignment measurement device adopted for a mainstream photoetching system is realized based on a grating diffraction beam interference principle, namely, a grating mark is used as a measurement reference, and position information of the grating mark is calculated by extracting an interference alignment signal phase difference value of a grating mark multi-level diffraction beam. Because the grating mark is etched on the surface of the silicon wafer, and the silicon wafer is required to be subjected to chemical mechanical polishing, gluing, oxidization and other technological processes, the grating mark can be subjected to asymmetric deformation, so that the strength of a detection signal is weakened, an additional phase difference can be added to the signal, the calculated position information has larger deviation, the performance of an alignment measuring device is finally influenced, and the technological adaptability of the device is reduced. Secondly, the grating mark size is close to the wavelength magnitude of the illumination beam, and factors such as the polarization state of the laser beam, light intensity fluctuation, stray light inside the system and the like can greatly influence the phase measurement precision of an alignment signal, and finally the alignment precision of the device can be reduced. Therefore, the technical problem that needs to be solved urgently by those skilled in the art is how to ensure that the system generates high enough signal intensity and effectively inhibit the influence of factors such as the polarization state of the laser beam, the fluctuation of the light intensity and the scattered light inside the system on the quality of the alignment signal when the size of the grating mark is continuously reduced to the wavelength level of the illumination beam and the grating mark is subjected to the processes such as chemical mechanical polishing, gluing and oxidization. Disclosure of Invention The invention aims to overcome the defects of the prior art and provides a grating diffraction beam interference off-axis alignment measuring device. The four-channel beam combiner is used for combining four laser beams with different wavelengths to realize illumination of grating marks, so tha