CN115576041B - Crystal alignment method - Google Patents

Abstract

The method for precisely aligning the crystal orientation provided by the application is used for positioning the crystal orientation of the silicon wafer; acquiring a reference grating parallel to the crystal direction of a silicon wafer; placing a grating substrate to be exposed with a reference grating on a precise turntable; moving the precise turntable to enable the left and right exposure beams positioned on the precise turntable to generate diffraction light in the normal direction of the grating substrate; rotating the precise turntable to enable the two beams of diffracted light to coincide and obtain an interference pattern; the precise turntable is adjusted to make the interference fringe period of the interference pattern reach the maximum value, and the static alignment is completed, the method for precisely aligning the crystal orientation provided by the application introduces a reference grating with a grating period matched with the interference field period of the SBIL system as an intermediate process, the method avoids introducing extra elements into the SBIL system, transfers a long-time-consuming process into ultraviolet lithography equipment, and improves the use efficiency of the SBIL system.

Description

A method for crystal alignment

Technical Field

The present application relates to the technical field of micro-nano structure processing, and in particular to a method for crystal orientation alignment.

Background Art

High aspect ratio silicon grating (HARSG) is an important short-wave optical device with wide applications in X-ray imaging and spectral detection systems. Among them, high aspect ratio silicon gratings with high line density (greater than 3000gr/mm) are key components of soft X-ray band energy spectrum detection systems. At present, the production technology of high aspect ratio silicon grating can be divided into three types: anisotropic wet etching of single crystal silicon in alkaline solution, deep reactive ion etching based on etching-passivation process (Bosch process), and metal-assisted chemical etching. In the first two technical routes, due to the requirements of aspect ratio and sidewall roughness, it is a necessary technology to keep the <111> crystal direction of the silicon substrate precisely parallel to the grating line direction. Metal-assisted chemical etching can get rid of the limitation of crystal direction, but the existing process is still difficult to produce high aspect ratio silicon gratings with high line density and large area (greater than cm level). Therefore, the precise alignment of the high line density grating line direction with the <111> crystal direction of the silicon wafer is an important technical difficulty.

High-line density grating masks can be prepared by scanning beam interference lithography (SBIL) technology. In this process, the stripe direction of the interference field in the SBIL system needs to be aligned with the <111> crystal direction of the substrate. The existing technical solution is a method proposed by M.Ahn to implant a microscopic imaging system into the SBIL system: first, through the fan-shaped mask pre-etching technology, a specific narrow rectangular silicon structure is used to characterize the <111> crystal direction of the wafer; then the wafer is placed on the workbench of the SBIL system, and the workbench is moved in the scanning direction. Through the relative movement of the narrow rectangle and the microscope collimator, the direction of the wafer can be gradually adjusted until the microscope collimator remains inside the rectangle during the movement. Finally, exposure is performed. At this time, the <111> crystal direction is consistent with the grating stripe direction obtained after photolithography, and the alignment error is within 0.05°.

The above-mentioned M.Ahn method can make the grating mask produced by the SBIL system consistent with the <111> crystal orientation of the silicon wafer. However, this requires adding the optical elements of the microscopic imaging system to the already complex SBIL system, which will increase the complexity of the system and increase the difficulty of optical path design and adjustment. In addition, it is difficult to align the narrow rectangular silicon structure representing the <111> crystal orientation with the microscope collimator. Since adjustments need to be made repeatedly during alignment and continuous observation is required during the movement, the alignment process takes a long time, which will reduce the efficiency of the SBIL system.

Summary of the invention

In view of this, it is necessary to provide a method for achieving high-precision alignment while improving alignment efficiency and avoiding the introduction of crystal orientation precise alignment of other components in the SBIL system in view of the defects existing in the prior art.

To solve the above problems, this application adopts the following technical solutions:

One of the purposes of the present application is to provide a method for precise crystal alignment, comprising the following steps:

Perform crystal orientation positioning on silicon wafers;

Acquiring a reference grating parallel to the crystal direction of the silicon wafer;

Placing the grating substrate to be exposed and carrying the reference grating on a precision turntable;

Moving the precision turntable so that the two exposure light beams on the left and right of the precision turntable both generate diffracted light in the normal direction of the grating substrate;

Rotating the precision turntable to make the two diffracted light beams overlap and obtain an interference pattern;

The precision turntable is adjusted so that the interference fringe period of the interference pattern reaches a maximum value, and the static alignment is completed.

In some of the embodiments, the step of performing crystal orientation positioning on the silicon wafer specifically includes the following step: performing <111> crystal orientation positioning on the silicon wafer by using a fan-shaped mask pre-etching technology.

In some of the embodiments, the step of obtaining a reference grating parallel to the crystal direction of the silicon wafer specifically includes the following steps: making a reference grating parallel to the crystal direction by ultraviolet contact lithography equipment.

In some of the embodiments, in the step of placing the silicon wafer to be exposed with the reference grating and the photoresist on a precision turntable, the precision turntable is a two-dimensional motion worktable.

In some of the embodiments, the two-dimensional motion workbench is pulled by a linear motor and moves along a scanning direction and a stepping direction respectively, and the scanning direction and the stepping direction are perpendicular to each other.

In some embodiments, the ruling direction of the reference grating is parallel to the scanning direction.

In some embodiments, in the step of moving the precision turntable, both the left and right exposure light beams on the precision turntable will generate diffracted light in the normal direction; specifically including the following steps:

The precision turntable is moved so that the interference field is located on the reference grating, and the left and right exposure beams located on the precision turntable overlap on the surface of the reference grating, and both the left and right exposure beams generate diffraction light in the normal direction of the grating base.

In some embodiments, the step of rotating the precision turntable to make the two diffracted light beams overlap and obtain the interference pattern specifically includes the following steps:

Two beams of diffracted light generated in the normal direction of the grating substrate are incident on the CCD on one side through the upper plane mirror, and then a real-time light intensity distribution image on the CCD is obtained by a computer.

In some embodiments, the step of adjusting the precision turntable so that the interference fringe period of the interference pattern reaches a maximum value and the static alignment is completed specifically includes the following steps:

By adjusting the precision turntable, interference fringes appear in the spot image, and then slowly adjusting the precision turntable to make the period of the interference fringes reach a maximum value, the static alignment is completed at this time, the period reaches the maximum value, that is, the period is greater than the diameter of the spot, and no complete periodic fringes can be observed within the spot range.

In some embodiments, the step of adjusting the precision turntable so that the interference fringe period of the interference pattern reaches a maximum value and the static alignment is completed specifically includes the following steps:

The precision turntable is adjusted to move at a uniform speed in the scanning direction. The reference grating and the left and right exposure beams produce relative movement, and a phase difference is generated between the two diffracted beams that changes linearly with the moving distance, thereby producing a periodic change in light intensity at each point on the light spot of the interference pattern, and the change period is inversely proportional to the alignment angle error.

In some embodiments, in the step of adjusting the precision turntable so that the interference fringe period of the interference pattern reaches a maximum value and the static alignment is completed, the following steps are also included:

After each movement of the precision turntable is completed, the angle of the precision turntable is adjusted, and then the precision turntable is adjusted to move in the opposite direction, and the above process is repeated until the turntable position with the largest change cycle is found. At this time, the position of the precision turntable is kept unchanged to complete the dynamic alignment process.

After the dynamic alignment process is completed, the following steps are also included: the remaining area of the grating substrate is exposed by moving the precision turntable, and after the development is completed, a high-line density grating mask that is precisely parallel to the direction of the silicon wafer can be obtained.

This application adopts the above technical solution, and its beneficial effects are as follows:

The present application provides a method for precise crystal alignment, which includes positioning the crystal orientation of a silicon wafer; obtaining a reference grating parallel to the crystal orientation of the silicon wafer; placing a grating substrate to be exposed with the reference grating on a precision turntable; moving the precision turntable so that the two exposure light beams on the left and right of the precision turntable both generate diffracted light in the normal direction of the grating substrate; rotating the precision turntable so that the two diffracted light beams overlap and obtain an interference pattern; adjusting the precision turntable so that the interference fringe period of the interference pattern reaches a maximum value, and static alignment is completed. The present application provides a method for precise crystal alignment, which introduces a reference grating whose grating period matches the interference field period of the SBIL system as an intermediate process, thereby avoiding the introduction of additional components in the SBIL system, and transferring the time-consuming process to the ultraviolet lithography equipment, thereby improving the use efficiency of the SBIL system, and enabling the interference fringes of the SBIL system to be precisely aligned with the <111> crystal orientation on the (110) silicon wafer surface, thereby obtaining an ultra-high etching rate ratio in the wet etching process, and preparing high-quality, high-line-density, high-aspect-ratio single-crystal silicon gratings.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments of the present application or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

FIG. 1 is a flow chart of the steps of the method for precise crystal alignment provided in the present application.

FIG2 is a schematic diagram of the interference fringe alignment between the reference grating and the scanning interference field exposure system used in the present application;

FIG3 is a schematic diagram of the alignment method based on the reference grating and the SBIL system used in the present application;

FIG. 4 is a schematic diagram of the dynamic alignment process of the relative movement between the reference grating and the exposure field in the x direction provided by the application.

DETAILED DESCRIPTION

Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present application, and should not be construed as limiting the present application.

In the description of the present application, it should be understood that the terms "upper", "lower", "horizontal", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

In order to make the objectives, technical solutions and advantages of the present application more clearly understood, the present application is further described in detail below in conjunction with the accompanying drawings and embodiments.

Please refer to FIG. 1 , which is a flow chart of the steps of a method for precise crystal alignment provided in the present embodiment 1, including the following steps S110 to S160 . The implementation method of each step is described in detail below.

Step S110: performing crystal orientation positioning on the silicon wafer.

In some of the embodiments, the step of performing crystal orientation positioning on the silicon wafer specifically includes the following step: performing <111> crystal orientation positioning on the silicon wafer by using a fan-shaped mask pre-etching technology.

It can be understood that in the step of crystal orientation positioning of the silicon wafer, the same method as the prior art is adopted, and the substrate used is a (110) single crystal silicon wafer, and the surface is covered with a 40nm thick silicon nitride layer. A fan-shaped spoke-type photoresist mask is made near the <111> crystal orientation by ultraviolet contact lithography, and the angle interval between the spokes is 0.03°, and then the mask is transferred to the silicon nitride layer by reactive ion etching. The wafer is etched in potassium hydroxide, and the lateral etching width of each spoke is positively correlated with the angle between it and the <111> crystal orientation. The lateral etching width of each spoke is measured under a microscope, and the spoke with the shortest lateral etching is considered to be parallel to the <111> crystal orientation, and its maximum error is half of the angle interval, that is, 0.015°.

Step S120: Acquire a reference grating parallel to the crystal direction of the silicon wafer.

In this embodiment, the step of obtaining a reference grating parallel to the crystal direction of the silicon wafer specifically includes the following steps: manufacturing a reference grating parallel to the crystal direction by using ultraviolet contact lithography equipment.

Specifically, the reference grating is made by ultraviolet contact lithography equipment, and the pattern on the mask used includes a reference grating pattern and a slit parallel to the reference grating. First, Shipley 1805 photoresist is spin-coated on the surface of the wafer, and the slits on the mask are aligned with the spokes selected in step one through a contact lithography system with a microscope, and the area near the edge of the substrate is exposed, and developed in a sodium hydroxide solution to obtain a reference grating mask. The period of the grating pattern on the mask should be an even multiple of the period of the interference field fringes in the scanning interference field exposure system to achieve diffraction in the normal direction. After the development is completed, the reference grating pattern is transferred to the substrate by a dry etching device. After cleaning, Shipley 1805 photoresist is spin-coated again, and pre-baked to prepare for alignment and exposure.

Step S130: placing the grating substrate to be exposed with the reference grating on a precision turntable.

In some embodiments, the precision turntable is a two-dimensional motion worktable. The double guide rails in the scanning motion direction of the two-dimensional motion worktable are perpendicular to the double guide rails in the stepping motion direction. The worktable is pulled by a linear motor and can move in the scanning direction and the stepping direction respectively, and the scanning direction is strictly parallel to the direction of the interference field stripes. When placing the substrate to be exposed, the direction of the lines of the reference grating should be roughly parallel to the scanning direction.

Step S140: moving the precision turntable so that the two exposure light beams on the left and right of the precision turntable both generate diffraction light in the normal direction of the grating substrate.

Please refer to Figure 2, which is a schematic diagram of the interference fringe alignment between the reference grating and the scanning interference field exposure system provided in this embodiment, wherein there are a left exposure beam 1, a right exposure beam 2, mirrors 4, 5, 6, 7, 8, 9, a substrate 10 with a reference grating, a precision turntable 11, a two-dimensional workbench 12, diffraction beams 13, 14 of the reference grating, and a CCD 15.

It can be understood that the precision turntable 11 is moved so that the interference field is located on the reference grating, and the left and right exposure light beams 1, 2 pass through the reflecting mirrors 3, 4, 5, 6, 7, 8 and overlap on the substrate 10 with the reference grating to form an exposure field. Since the reference period is an even multiple of the interference field fringe period, the left and right exposure light beams 1, 2 will both generate diffraction light in the normal direction.

Step S150: Rotate the precision turntable to make the two diffracted light beams overlap and obtain an interference pattern.

In some of the embodiments, the step of rotating the precision turntable to make the two diffracted light beams overlap and obtain the interference pattern specifically includes the following steps: the two diffracted light beams generated in the normal direction of the grating substrate are incident on the CCD on one side through the upper plane mirror, and then the real-time light intensity distribution image on the CCD is obtained by a computer.

It should be pointed out that the plane mirror 7 is not an additional element introduced to realize the present invention. Its original function in the SBIL system is to make the scanning direction of the workbench strictly parallel to the direction of the interference fringes during system construction and debugging.

Please refer to Figure 3, which is a schematic diagram of the alignment method based on the reference grating and the SBIL system provided in this embodiment, wherein: interference field exposure beams 1, 2; grating area 3 to be exposed; reference grating area 4; interference light field 5 formed by diffracted light in the normal direction; interference light fields 6, 7 formed by other orders of diffracted light in non-normal directions.

In the SBIL system, the two beams 1 and 2 of the exposure light field are incident on the reference grating area 4 of the wafer, and the diffracted light 8 of the two exposure beams is received by the CCD detector through the mirror reflection above the wafer. Due to the difference in diffraction efficiency of different orders, the interference fringes 5 produced by the ±m-order diffracted light have the best contrast. The period of the reference grating 4 is set to an even multiple of the interference field period. When the two coherent light beams of the exposure system are located in the main plane of the grating, ideally two overlapping diffracted light beams will be generated in the normal direction 4 of the reference grating surface. If there is a deviation between the grating line direction of the reference grating 4 and the direction of the interference field fringes, the left and right light beams 1 and 2 will undergo conical diffraction on the reference grating, causing the two diffracted light beams 1 and 2 to deviate from the normal 8 direction, thereby generating interference and fringes in the coherent area of the diffracted light beams on the detector.

Step S160: adjusting the precision turntable so that the interference fringe period of the interference pattern reaches a maximum value, and the static alignment is completed.

It can be understood that since the period of the interference fringes generated by the diffracted light is inversely proportional to the deflection angle, a precision turntable is used to finely adjust the direction of the wafer in the SBIL system to maximize the period of the interference fringes. After the interference field is moved to the reference grating area 4, the alignment operation is performed by adjusting the turntable. When the maximum period of the interference fringes is observed, the exposure process is directly performed through the relative movement between the interference field and the wafer. In some embodiments, the step of adjusting the precision turntable so that the period of the interference fringes appearing in the interference pattern reaches the maximum value and the static alignment is completed specifically includes the following steps:

By adjusting the precision turntable, interference fringes appear in the spot image, and then slowly adjusting the precision turntable to make the period of the interference fringes reach a maximum value, the static alignment is completed at this time, the period reaches the maximum value, that is, the period is greater than the diameter of the spot, and no complete periodic fringes can be observed within the spot range.

Please refer to Figure 4, which is a schematic diagram of the dynamic alignment process of the relative movement between the reference grating and the exposure field in the x-direction provided in this embodiment, wherein: interference field exposure beams 1, 2 before movement; interference field exposure beams 3, 4 after movement; interference pattern 5 before movement; interference pattern 6 after movement.

It can be understood that when the fringe period is larger than the spot size of the receiving plane, the accuracy of the alignment process can be further improved by the additional phase change caused by the movement of the reference grating in the SBIL system. When the wafer moves along the scanning direction X, due to the angle deviation α between the grating lines and the exposure field fringes, the movement of the exposure field perpendicular to the grating lines in the Y direction will cause a phase difference between the two diffracted beams, resulting in periodic changes in the light intensity on the receiving surfaces 5 and 6. Therefore, ultra-high alignment accuracy between the reference grating and the interference fringes can be achieved through the dynamic alignment process.

In some embodiments, the step of adjusting the precision turntable so that the interference fringe period of the interference pattern reaches a maximum value and the static alignment is completed specifically includes the following steps:

The precision turntable is adjusted to move at a uniform speed in the scanning direction. The reference grating and the left and right exposure beams produce relative movement, and a phase difference is generated between the two diffracted beams that changes linearly with the moving distance, thereby producing a periodic change in light intensity at each point on the light spot of the interference pattern, and the change period is inversely proportional to the alignment angle error.

Step S160: After the step of adjusting the precision turntable so that the interference fringe period of the interference pattern reaches a maximum value and the static alignment is completed, the following steps are also included:

After each movement of the precision turntable is completed, the angle of the precision turntable is adjusted, and then the precision turntable is adjusted to move in the opposite direction, and the above process is repeated until the turntable position with the largest change cycle is found. At this time, the position of the precision turntable is kept unchanged, and the dynamic alignment process is completed.

Specifically, the workbench is moved 10 mm in the scanning direction of the workbench at a speed of 0.5 mm/s. At this time, the interference pattern observed by the CCD undergoes periodic changes in brightness, indicating that the reference grating is displaced in a direction perpendicular to the grating lines, that is, there is an angular error between the grating line direction and the scanning direction of the reference grating. The turntable is further adjusted until the interference pattern does not produce obvious changes in brightness during the movement. At this time, it indicates that the reference grating is consistent with the scanning direction, that is, the grating line direction of the reference grating is consistent with the interference fringe direction. The alignment accuracy of this process is limited by the size of the reference grating and the moving distance. For a moving distance of 10 mm, the angular alignment error can be controlled to 0.001°.

Step S180: After the dynamic alignment process is completed, the following steps are also included:

The remaining area of the grating substrate is exposed by moving the precision turntable, and after development is completed, a high-line density grating mask that is precisely parallel to the direction of the silicon wafer can be obtained.

It can be understood that after the adjustment is completed, the angle of the precision turntable is kept unchanged, and the worktable is controlled to move so that the interference field spot formed by the exposure beam moves out of the reference grating area and returns to the initial position. The worktable movement is controlled to perform the exposure process. After the exposure and development are completed, a high-line density grating mask parallel to the <111> crystal direction of the wafer can be obtained.

The method for precise crystal orientation alignment provided by the present application avoids the introduction of additional components into the SBIL system by introducing a reference grating whose grating period matches the interference field period of the SBIL system as an intermediate process, and transfers the time-consuming process to the ultraviolet lithography equipment, thereby improving the utilization efficiency of the SBIL system, and enabling the interference fringes of the SBIL system to be precisely aligned with the <111> crystal orientation on the (110) silicon wafer surface, thereby obtaining an ultra-high etching rate ratio in the wet etching process, and preparing high-quality, high-line-density, high-aspect-ratio single-crystal silicon gratings.

It can be understood that the technical features of the above-described embodiments can be arbitrarily combined. In order to make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

The above are only preferred embodiments of the present application, and only specifically describe the technical principles of the present application. These descriptions are only for explaining the principles of the present application and cannot be interpreted in any way as limiting the scope of protection of the present application. Based on the explanation here, any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application, and other specific implementation methods of the present application that can be associated with by technicians in this field without creative work, should be included in the scope of protection of the present application.

Claims (12)

1. A method for crystal alignment, comprising the following steps: Perform crystal orientation positioning on silicon wafers; Acquiring a reference grating parallel to the crystal direction of the silicon wafer; Placing the grating substrate to be exposed and carrying the reference grating on a precision turntable; Moving the precision turntable so that the two exposure light beams on the left and right of the precision turntable both generate diffracted light in the normal direction of the grating substrate; Rotating the precision turntable to make the two diffracted light beams overlap and obtain an interference pattern; The precision turntable is adjusted so that the interference fringe period of the interference pattern reaches a maximum value, and the static alignment is completed. 2. The method for crystal orientation alignment as claimed in claim 1, characterized in that, in the step of performing crystal orientation positioning on the silicon wafer, the following step is specifically included: performing <111> crystal orientation positioning on the silicon wafer by using a fan-shaped mask pre-etching technology. 3. The method for crystal orientation alignment as described in claim 1 is characterized in that, in the step of obtaining a reference grating parallel to the crystal orientation of the silicon wafer, the following step is specifically included: making a reference grating parallel to the crystal orientation by ultraviolet contact lithography equipment. 4. The method for crystal alignment as described in claim 1 is characterized in that in the step of placing the silicon wafer to be exposed with the reference grating and the photoresist on a precision turntable, the precision turntable is a two-dimensional motion worktable. 5. The method for crystal alignment as described in claim 4 is characterized in that the two-dimensional motion workbench is pulled by a linear motor and moves along a scanning direction and a stepping direction respectively, and the scanning direction and the stepping direction are perpendicular to each other. 6 . The method for crystal alignment as claimed in claim 5 , wherein the direction of the lines of the reference grating is parallel to the scanning direction. 7. The method for crystal alignment according to claim 1, characterized in that, in the step of moving the precision turntable so that the two exposure light beams on the left and right of the precision turntable both generate diffracted light in the normal direction, the method specifically comprises the following steps: The precision turntable is moved so that the interference field is located on the reference grating, and the left and right exposure beams located on the precision turntable overlap on the surface of the reference grating, and both the left and right exposure beams generate diffraction light in the normal direction of the grating base. 8. The method for crystal alignment according to claim 1, characterized in that the step of rotating the precision turntable to make the two diffracted light beams overlap and obtain the interference pattern specifically comprises the following steps: Two beams of diffracted light generated in the normal direction of the grating substrate are incident on the CCD on one side through the upper plane mirror, and then a real-time light intensity distribution image on the CCD is obtained by a computer. 9. The method for crystal alignment according to claim 1, characterized in that, in the step of adjusting the precision turntable so that the interference fringe period of the interference pattern reaches a maximum value and static alignment is completed, the following steps are specifically included: By adjusting the precision turntable, interference fringes appear in the spot image, and then slowly adjusting the precision turntable to make the period of the interference fringes reach a maximum value, the static alignment is completed at this time, the period reaches the maximum value, that is, the period is greater than the diameter of the spot, and no complete periodic fringes can be observed within the spot range. 10. The method for crystal alignment according to claim 9, characterized in that the step of adjusting the precision turntable so that the interference fringe period of the interference pattern reaches a maximum value and the static alignment is completed specifically comprises the following steps: The precision turntable is adjusted to move at a uniform speed in the scanning direction. The reference grating and the left and right exposure beams produce relative movement, and a phase difference is generated between the two diffracted beams that changes linearly with the moving distance, thereby producing a periodic change in light intensity at each point on the light spot of the interference pattern, and the change period is inversely proportional to the alignment angle error. 11. The method for crystal alignment according to claim 10, characterized in that, in the step of adjusting the precision turntable so that the interference fringe period of the interference pattern reaches a maximum value and the static alignment is completed, the following step is also included: After each movement of the precision turntable is completed, the angle of the precision turntable is adjusted, and then the precision turntable is adjusted to move in the opposite direction, and the above process is repeated until the turntable position with the largest change cycle is found. At this time, the position of the precision turntable is kept unchanged to complete the dynamic alignment process. 12. The method for crystal alignment according to claim 11, characterized in that it further comprises the following steps after completing the dynamic alignment process: The remaining area of the grating substrate is exposed by moving the precision turntable, and after development is completed, a high-line density grating mask that is precisely parallel to the direction of the silicon wafer can be obtained.