A multi-wavelength echelette fringe array mark alignment levelling system and method

Abstract

The application discloses a kind of multi-wavelength grating stripe array mark alignment leveling system and method, including scanning motion platform, mask table, laser light source, coupler, collimating expander, mask alignment mark grating, substrate alignment mark grating, beam splitter prism, camera.Laser light source controls to emit parallel light source, pass through coupler and carry out beam coupling, then again after collimating expander carries out the adjustment of incident spot size, then vertically incident to mask alignment mark grating and diffract;Through the diffracted light of mask alignment mark grating, substrate alignment mark grating again occurs diffraction and reflection, after three grating modulation, each harmonic occurs moiré interference after harmonic, is received by objective, then by camera moiré interference stripe is recorded;After combining, multi-wavelength light source is superimposed integral according to weight proportion by different waveband;By the received moiré stripe image is preprocessed, in phase extraction and analysis, finally solve out alignment offset.

Description

Technical Field

[0001] The embodiments of the present invention relate to photolithography technology, and more particularly to a multi-wavelength stacked grating array marking alignment and leveling system and method. Background Technology

[0002] Photolithography, the most critical process in the manufacturing of large-scale integrated circuits, uses lasers to image mask patterns onto substrates such as wafers. The fabrication of a single chip requires hundreds of exposures, and the misalignment between the current layer's pattern and the previous reference layer's pattern after each exposure is called overlay error. According to predictions from the International Relationship Data Center (IRDS), by 2023, the overlay error requirement for chip manufacturing will be less than 2 nanometers, posing a significant challenge to alignment systems.

[0003] Currently, the mainstream alignment methods include alignment measurement methods based on geometric patterns, alignment methods based on light intensity signal analysis, alignment measurement methods based on zone plates, alignment measurement methods based on grating diffraction interference, and alignment measurement methods based on moiré fringes.

[0004] Traditional moiré fringe alignment methods are all image-processing-based, resulting in high computational costs, low alignment accuracy, and difficulty in handling rotational errors introduced by the deflection of alignment marks. Since the formation of moiré interference fringes is limited by the Talbot principle, the alignment process requires precise control of the spacing between mask and substrate marks, which significantly reduces the adaptability of photolithography processes. Therefore, there is an urgent need for a photolithography alignment method that expands the limitations of moiré interference fringe alignment in terms of gap control. Summary of the Invention

[0005] The purpose of this invention is to provide a multi-wavelength stacked grating array marking alignment and leveling system and method for monitoring the tilt between the substrate and the mask, as well as the positional deviation between the substrate pattern and the mask pattern.

[0006] This invention utilizes a multi-wavelength light source through a mask alignment mark grating. The multiple wavelengths create an ultra-long Talbot distance behind the grating. When the substrate alignment mark is located within this Talbot distance, clear moiré fringe imaging is achieved, thereby extending the distance between the substrate and the mask and improving process adaptability. To address the issue of resolving the mask-substrate misalignment, image filtering, averaging, and rotation angle compensation are used to reduce introduced errors and improve alignment accuracy.

[0007] The technical solution of this invention is as follows: a multi-wavelength grating stripe array marking alignment and leveling system, comprising a workpiece stage, a scanning motion stage, an alignment and leveling detection system, a mask, a substrate, and an imaging system. The imaging system includes a beam splitter, an objective lens group, and a CCD camera. The alignment and leveling detection system further includes a mask stage, a first laser source, a second laser source, a third laser source, a fourth laser source, a coupler, and a collimator and beam expander. The first, second, third, and fourth mask alignment marks and the first, second, third, and fourth substrate alignment marks are located on the mask and the substrate, respectively. The scanning motion stage is at the top of the system, and there are two alignment and leveling detection systems on the left and right sides, respectively. The two systems have the same structure but different positions. The imaging system is connected by screws. Fixed on the scanning stage, the positions of the two imaging systems are symmetrical about the central axis of the scanning stage. Four laser sources, along with couplers and collimators / expanders, are connected by optical fibers to the beam splitter of the imaging system on the side of the scanning stage. Below the beam splitter of the imaging system are the mask stage and the workpiece stage. The substrate is placed on the upper surface of the workpiece stage, and a mask is placed on the mask stage above the substrate. The laser sources enter the imaging system through the couplers and collimators / expanders, and after passing through the beam splitter, they are incident on the mask alignment mark grating and the substrate alignment mark grating, causing diffraction. The reflected light re-enters the objective lens group and forms an image at the CCD camera. By performing phase extraction and analysis on the fringe image received by the CCD camera, the offset is derived to compensate for the alignment position deviation.

[0008] The beneficial effects of this invention are:

[0009] This invention features a simple and clear structure. Compared to traditional moiré fringe alignment techniques, the reflective device employed in this invention improves the integration of the equipment and reduces its space occupancy. The use of multiple wavelength lasers for coupling increases the usable depth of focus between the mask alignment mark grating and the substrate alignment mark grating, while significantly enhancing the signal strength of the moiré interference fringes. This invention is highly practical. In near-field lithography alignment applications, no additional components are required; simply changing the light source type effectively relaxes the gap restriction between the mask alignment grating and the substrate alignment grating, greatly improving the applicability and flexibility of near-field lithography alignment technology. In the fine alignment section, errors introduced by image rotation angles are considered and compensated for, as are errors introduced by noise and defects, significantly improving the alignment accuracy between the substrate and the mask. Attached Figure Description

[0010] The specific structural form of the multi-wavelength stacked grating array marker alignment and leveling method described in this invention is further illustrated in the accompanying drawings:

[0011] Figure 1 A structural diagram of a multi-wavelength stacked grating stripe array marker alignment and leveling system provided by the present invention;

[0012] Figure 2 This is a distribution diagram of mask alignment marks on the mask plate;

[0013] Figure 3 This is a distribution diagram of substrate alignment marks on the substrate;

[0014] Figure 4 Diagram of the grating structure for mask alignment marks;

[0015] Figure 5 Diagram of the substrate alignment mark grating structure;

[0016] Figure 6 Flowchart for substrate leveling and alignment;

[0017] Figure 7 This is a flowchart of the alignment signal processing.

[0018] In the figure, the reference numerals are as follows: 1.1-Left side alignment and leveling detection system, 1.2-Right side alignment and leveling detection system, 2-Imaging system, 3-Scanning stage, 4-Mask stage, 5-Mask plate, 6-Substrate, 7-Workpiece stage, 8-First laser source, 9-Second laser source, 10-Third laser source, 11-Fourth laser source, 12-Coupler, 13-Collimator and beam expander, 14-Beam splitter, 15-Objective lens group, 16-CCD camera, 171-First mask alignment mark, 172-Second mask alignment mark, 173-Third mask alignment mark, 174-Fourth mask alignment mark, 181-First substrate alignment mark, 182-Second substrate alignment mark, 183-Third substrate alignment mark, 184-Fourth substrate alignment mark, 191-Upper grating of the first X-direction fine alignment mark of the mask, 192-Lower grating of the first X-direction fine alignment mark of the mask, 20 1 - Left grating of the first Y-direction fine alignment mark of the mask; 202 - Right grating of the first Y-direction fine alignment mark of the mask; 211 - Upper grating of the second X-direction fine alignment mark of the mask; 212 - Lower grating of the second X-direction fine alignment mark of the mask; 221 - Left grating of the second Y-direction fine alignment mark of the mask; 222 - Right grating of the second Y-direction fine alignment mark of the mask; 231 - Coarse alignment mark of the mask; 193 - Upper grating of the first X-direction fine alignment mark of the substrate; 194 - Lower grating of the first X-direction fine alignment mark of the substrate; 203 - Left grating of the first Y-direction fine alignment mark of the substrate; 204 - Right grating of the first Y-direction fine alignment mark of the substrate; 213 - Upper grating of the second X-direction fine alignment mark of the substrate; 214 - Lower grating of the second X-direction fine alignment mark of the substrate; 223 - Left grating of the second Y-direction fine alignment mark of the substrate; 224 - Right grating of the second Y-direction fine alignment mark of the substrate; 232 - Coarse alignment mark of the substrate. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention. Furthermore, the technical features involved in the various embodiments of this invention described below can be combined with each other as long as they do not conflict with each other. To achieve the above objectives, this invention adopts the following technical solution.

[0020] like Figure 1 As shown, a multi-wavelength grating stripe array marking alignment and leveling system is disclosed. It includes: a left alignment and leveling detection system 1.1, a right alignment and leveling detection system 1.2, a scanning stage 3, a mask 5, a substrate 6, and a workpiece stage 7. The alignment and leveling detection system includes: an imaging system 2, a mask stage 4, a first laser source 8, a second laser source 9, a third laser source 10, a fourth laser source 11, a coupler 12, and a collimator and beam expander 13. First, second, third, and fourth mask alignment marks 171, 172, 173, and 174, and first, second, third, and fourth substrate alignment marks 181, 182, 183, and 184 are located on the mask 5 and substrate 6, respectively. The imaging system 2 includes: a beam splitter prism 14, an objective lens group 15, and a CCD camera 16. The scanning stage 3 is located at the top of the entire system, with a left alignment and leveling detection system 1.1 and a right alignment and leveling detection system 1.2 positioned on its left and right sides respectively. The left and right alignment and leveling detection systems 1.1 and 1.2 have identical structures but are positioned differently. The entire imaging system 2 is fixed to the scanning stage 3 with screws, and the positions of the two imaging systems 2 are symmetrical about the central axis of the scanning stage 3. A first laser source 8, a second laser source 9, a third laser source 10, a fourth laser source 11, a coupler 12, and a collimator / expander 13 are connected via optical fibers to the beam splitter 14 of the imaging system 2 from the side of the scanning stage 3. A mask stage 4 and a workpiece stage 7 are located at a certain distance below the imaging system 2. The laser source emits a parallel light source, which is coupled through coupler 12, and then the incident light spot size is adjusted by collimator expander 13. The light is then perpendicularly incident on the grating in the mask alignment mark of the mask plate 5 and diffracted. The diffracted light through the grating in the mask alignment mark is diffracted and reflected again by the alignment mark grating on the substrate 6. After being modulated by the third grating, the harmonics of each order undergo moiré interference and are received by the objective lens group 15. The moiré interference fringes are then recorded by CCD camera 16. The multi-wavelength light source after beam combining enhances the light intensity of the moiré interference fringes by superimposing and integrating different wavelengths according to weight ratios, thus expanding the effective formation range of the moiré interference fringes. The moiré fringe image is preprocessed, and then phase extraction and analysis are performed to finally calculate the alignment offset. The CCD camera 16 is a high-sensitivity CCD camera.

[0021] The parallel light source consists of four single-wavelength laser sources combined into a single parallel light source with adjustable intensity and beam size via coupler 12 and collimator 13. The laser sources include first, second, third, and fourth laser sources 8, 9, 10, and 11. The objective lens 15 has an adjustable magnification of 2 to 9 times. The first, second, third, and fourth mask alignment marks 171, 172, 173, and 174, and the first, second, third, and fourth substrate alignment marks 181, 182, 183, and 184 are four-quadrant phase gratings made of quartz material covered with Cr metal.

[0022] like Figure 2 As shown, the mask alignment marks on the mask plate 5 are phase gratings made of quartz material, and there are four of them, namely the first mask alignment mark 171, the second mask alignment mark 172, the third mask alignment mark 173, and the fourth mask alignment mark 174.

[0023] like Figure 4 As shown, the first, second, third, and fourth mask alignment marks 171, 172, 173, and 174 all include a coarse alignment mark 231 and four pairs of fine alignment marks: an upper grating 191 for the first X-direction fine alignment mark, a lower grating 192 for the first X-direction fine alignment mark, a left grating 201 for the first Y-direction fine alignment mark, a right grating 202 for the first Y-direction fine alignment mark, an upper grating 211 for the second X-direction fine alignment mark, a lower grating 212 for the second X-direction fine alignment mark, a left grating 221 for the second Y-direction fine alignment mark, and a right grating 222 for the second Y-direction fine alignment mark. The period of the upper row of gratings is 4µm, and the period of the lower row of gratings is 4.4µm.

[0024] like Figure 3 As shown, the substrate alignment marks on substrate 6 are also phase gratings made of quartz material, and there are four of them: the first substrate alignment mark 181, the second substrate alignment mark 182, the third substrate alignment mark 183, and the fourth substrate alignment mark 184.

[0025] like Figure 5 As shown, the first, second, third, and fourth substrate alignment marks 181, 182, 183, and 184 all include a coarse alignment mark 232 and four pairs of fine alignment marks: an upper grating 193 for the first X-direction fine alignment mark, a lower grating 194 for the first X-direction fine alignment mark, a left grating 203 for the first Y-direction fine alignment mark, a right grating 204 for the first Y-direction fine alignment mark, an upper grating 213 for the second X-direction fine alignment mark, a lower grating 214 for the second X-direction fine alignment mark, a left grating 223 for the second Y-direction fine alignment mark, and a right grating 224 for the second Y-direction fine alignment mark. The upper row of gratings has a period of 4.4 μm, and the lower row of gratings has a period of 4 μm.

[0026] like Figure 6 As shown, a method for aligning and leveling multi-wavelength stacked grating array markers according to the present invention includes the following steps:

[0027] Step 1: The light source, after being combined by the coupler 12 and the collimator expander 13, is incident perpendicularly on the mask alignment mark and the substrate alignment mark and then reflected back. The light, after being modulated three times, enters the imaging system 2 and is captured by the CCD camera 16. By observing the mask coarse alignment mark 231 in the mask alignment mark of the CCD camera 16, it is roughly nested in the center of the substrate coarse alignment mark 232 in the substrate alignment mark, thus completing the coarse alignment.

[0028] Since the numerical aperture of the detection system is small, and the mask's two diffraction orders, being of the same order, have the same emission direction after interacting with the same diffraction order of the substrate, the influence of the first diffraction by the mask is ignored. Only the effects of substrate diffraction and the second diffraction by the mask are considered. The complex amplitude of the moiré fringes received by the CCD camera 16 can be simplified to the expression for the complex amplitude of the moiré fringes when the light source undergoes n diffractions at the grating in the substrate alignment mark and m diffractions at the grating in the mask alignment mark:

[0029] ,

[0030] In the formula, m is the diffraction order of the diffracted beam in the mask alignment mark grating;

[0031] n—the diffraction order of the diffracted beam on the substrate aligned with the marking grating;

[0032] —The frequency of the alignment marks in the mask alignment mark grating. , It is the period of the mask alignment mark;

[0033] —The frequency of the alignment marks in the mask alignment mark grating. , It is the period of the substrate alignment marks;

[0034] (x,y) — represents the complex amplitude distribution in the xy coordinate system. The amplitude representing the complex amplitude distribution;

[0035] Phase information representing complex amplitude;

[0036] Due to limitations in system numerical aperture and light intensity, only the most easily distinguishable (1, -1), (0, 0), and (1, -1) moiré fringes formed on CCD camera 16 are accepted and analyzed to obtain the relative offset between the mask and the substrate. The distance between the grating mark and the target surface of CCD camera 16 is not constant. The z-axis distance expression is introduced into the complex amplitude of the moiré fringes as follows:

[0037] ,

[0038] In the formula, The constant phase delay in the nonlinear phase factor;

[0039] z is the distance the light source travels along the z-axis;

[0040] This refers to the frequency-dependent phase shift in the nonlinear phase factor.

[0041] Let x be the spatial frequency of the incident light field along the x-axis. , It is the period of the mask alignment mark;

[0042] Let x be the spatial frequency of the incident light field along the x-axis. , It is the period of the substrate alignment marks;

[0043] Ignoring the constant phase delay in the nonlinear phase factor, the intensity of the moiré interference fringe signal... It can be represented as:

[0044] ,

[0045] In the formula, These are the spectral weighting coefficients (coefficients used to weight the light intensity of different wavelengths in spectral analysis); Wavelength; for The conjugate;

[0046] When the distance z satisfies the condition:

[0047] ,

[0048] When k=1, 2..., the moiré fringe image is clearest. This is called the Talbot distance; the depth of focus (DOF) is defined by the brightness field width, and the different wavelengths of the combined light spectrum are within the Talbot distance. The integral on the surface can extend the depth of focus, and the extended DOF is:

[0049] ,

[0050] In the formula, N is the multiple of the extended Tabor distance substrate alignment mark grating;

[0051] Step 2: Drive the scanning stage 3 to lift the workpiece stage 7 upwards until the substrate 6 and the mask 5 are tightly attached and hold for a few seconds, then return to the original position to complete the leveling.

[0052] Step 3: Observe and correct the tilt angles of the first, second, third, and fourth mask alignment marks 171, 172, 173, and 174 relative to the first, second, third, and fourth substrate alignment marks 181, 182, 183, and 184.

[0053] Step 4: Flowchart as follows Figure 7 As shown, the recorded moiré interference fringe signal is converted into a digital image for precise alignment. The effective range is cropped using an image preprocessing algorithm, and the phase difference of the moiré interference fringes is calculated using Fourier transform to resolve the phase, thereby adjusting the relative positional relationship between the mask alignment marks and the substrate alignment marks.

[0054] Specifically, when the grating 191 on the mask first X-direction fine alignment mark in the first mask alignment mark 171 and the grating 193 on the substrate first X-direction fine alignment mark in the first substrate alignment mark 181 are offset... When the moiré fringe complex amplitude expression is given (taking the (-1,1) order as an example), it is:

[0055] ,

[0056] ,

[0057] in , The grating frequency of the grating in the mask alignment mark and the grating in the substrate alignment mark.

[0058] The complex amplitude distribution of moiré fringes is formed by superimposing the grating 191 on the mask first X-direction fine alignment mark in the first mask alignment mark 171 and the grating 193 on the substrate first X-direction fine alignment mark in the first substrate alignment mark 181;

[0059] The complex amplitude distribution of moiré fringes is formed by superimposing the grating 192 under the mask first X-direction fine alignment mark in the first mask alignment mark 171 and the grating 194 under the substrate first X-direction fine alignment mark in the first substrate alignment mark 181.

[0060] The period is and The grating co-formation period is Calculate the phase difference between the two gratings that form the moiré fringes:

[0061] ,

[0062] ,

[0063] ,

[0064] The offset between the mask and the substrate alignment mark grating can be calculated:

[0065] ,

[0066] This embodiment enables the extension of the Tybe distance, the leveling of the parallelism between the mask and the substrate, and the calculation of the offset between the mask and the substrate.

[0067] The design examples detailed in this invention are only used to illustrate the advantages and rationality of this invention. Any examples of optimized designs based on the technical solutions of this invention fall within the scope of this invention. The techniques and principles not described in detail in this invention are well known to those skilled in the art.

Claims

1. A multi-wavelength stacked grating array marker alignment and leveling system, characterized in that: The system includes a workpiece stage, a scanning motion stage, an alignment and leveling detection system, a mask, and a substrate. The alignment and leveling detection system includes an imaging system, which comprises a beam splitter, objective lens group, and CCD camera. The system also includes a mask stage, a first laser source, a second laser source, a third laser source, a fourth laser source, a coupler, and a collimator and beam expander. Alignment marks for the first, second, third, and fourth masks and the first, second, third, and fourth substrates are located on the mask and substrate, respectively. The scanning motion stage is at the top of the system, with two alignment and leveling detection systems on the left and right sides, respectively. These systems have the same structure but are positioned differently. The imaging systems are fixed to the scanning motion stage with screws. The system is symmetrical about the central axis of the scanning stage. Four laser sources, along with couplers and collimators / expanders, are connected by optical fibers to the side of the scanning stage and incident on the beam splitter of the imaging system. Below the beam splitter of the imaging system are the mask stage and the workpiece stage. The substrate is placed on the upper surface of the workpiece stage, and a mask is placed on the mask stage above the substrate. The laser sources enter the imaging system through the couplers and collimators / expanders, and after passing through the beam splitter, they are incident on the mask alignment mark grating and the substrate alignment mark grating, causing diffraction. The reflected light re-enters the objective lens group and forms an image at the CCD camera. By performing phase extraction and analysis on the fringe image received by the CCD camera, the offset is derived to compensate for the alignment position deviation. The laser source is coupled into a multi-wavelength light source with different weights for each band by a coupler; the collimator and beam expander are used to control the beam parallelism and beam spot size; the substrate and mask alignment mark grating is a four-quadrant phase grating made of quartz glass; the objective lens group is an adjustable magnifying objective lens used to receive the third diffracted beam; the CCD camera is used to record the image formed by the third diffracted beam.

2. The multi-wavelength stacked grating array marker alignment and leveling system according to claim 1, characterized in that: Place the substrate on the upper surface of the workpiece stage, place the mask on the mask stage, level it first, and then perform the alignment operation.

3. The multi-wavelength stacked grating array marker alignment and leveling system according to claim 1, characterized in that: The first, second, third, and fourth mask alignment marks all include coarse alignment marks and four pairs of fine alignment marks: the upper grating of the first X-direction fine alignment mark, the lower grating of the first X-direction fine alignment mark, the left grating of the first Y-direction fine alignment mark, the right grating of the first Y-direction fine alignment mark, the upper grating of the second X-direction fine alignment mark, the lower grating of the second X-direction fine alignment mark, the left grating of the second Y-direction fine alignment mark, and the right grating of the second Y-direction fine alignment mark. The period of the upper grating is 4µm, and the period of the lower grating is 4.4µm.

4. The multi-wavelength stacked grating array marker alignment and leveling system according to claim 3, characterized in that: The first, second, third, and fourth substrate alignment marks all include coarse alignment marks and four pairs of fine alignment marks: an upper grating for the first X-direction fine alignment mark, a lower grating for the first X-direction fine alignment mark, a left grating for the first Y-direction fine alignment mark, a right grating for the first Y-direction fine alignment mark, an upper grating for the second X-direction fine alignment mark, a lower grating for the second X-direction fine alignment mark, a left grating for the second Y-direction fine alignment mark, and a right grating for the second Y-direction fine alignment mark. The upper grating has a period of 4.4 μm, and the lower grating has a period of 4 μm.

5. An alignment and leveling method using a multi-wavelength stacked grating array marker alignment and leveling system according to any one of claims 1-4, characterized in that, Includes the following steps: Step 1: The laser light source, after being combined by the coupler and collimator, is incident perpendicularly on the mask alignment mark grating and the substrate alignment mark grating, and then reflected back. The light, after being modulated three times, enters the imaging system and is captured by the CCD camera. By observing the mask coarse alignment mark in the CCD camera mask alignment mark, it is nested in the center of the substrate coarse alignment mark of the substrate alignment mark, thus completing the coarse alignment. Step 2: Drive the motion table to lift the workpiece stage upwards until the substrate and the mask are tightly attached and hold for one second, then return to the original position to complete the leveling. Step 3: Correct the Rz rotation of the image. Here, rotation correction refers to the rotation correction of the substrate relative to the mask. Step 4: Fine alignment of mask and substrate; The image recorded by the CCD camera is preprocessed, including image filtering, image cropping, and image rotation correction. Then, Fourier transform is performed to extract phase information from the frequency domain. The phase difference between adjacent gratings at the same position after cropping is calculated, and the offset is obtained by solving the problem, thus completing the alignment operation between the mask and the substrate.

6. The method for aligning and leveling multi-wavelength stacked grating array markers according to claim 5, characterized in that: Step four is as follows: In the fine alignment step, first, the image is spatially filtered; then, the image tilt angle is corrected; the effective part of the image is cropped and the average value is taken along the X or Y direction; the image is Fourier transformed to extract the image phase in the frequency domain; the phase difference of the alignment mark is solved and converted into alignment deviation.

7. The method for aligning and leveling multi-wavelength stacked grating array markers according to claim 6, characterized in that, Step one is as follows: The complex amplitude of the moiré fringes received by the CCD camera, simplified to the complex amplitude of the moiré fringes after n diffractions at the substrate alignment mark grating and m diffractions at the mask alignment mark grating, is expressed as follows: ， In the formula, m is the diffraction order of the diffracted beam in the mask alignment mark grating; n—the diffraction order of the diffracted beam on the substrate aligned with the marking grating; —The frequency of the alignment marks in the mask alignment mark grating. , It is the period of the mask alignment mark; —The frequency of the alignment marks in the mask alignment mark grating. , It is the period of the substrate alignment marks; (x,y) — represents the complex amplitude distribution in the xy coordinate system. The amplitude representing the complex amplitude distribution; Phase information representing complex amplitude; The z-direction distance expression is introduced into the complex amplitude of the moiré fringes as follows: ， In the formula, The constant phase delay in the nonlinear phase factor; z is the distance the light source travels along the z-axis; This refers to the frequency-dependent phase shift in the nonlinear phase factor. Let be the spatial frequency of the incident light field along the x-axis. , It is the period of the mask alignment mark grating; Let x be the spatial frequency of the incident light field along the x-axis. , It is the period of the substrate alignment mark grating; Ignoring the constant phase delay in the nonlinear phase factor, the intensity of the moiré interference fringe signal... Represented as: ， In the formula, These are the spectral weighting coefficients; Wavelength; for Conjugate; When the distance z satisfies the condition: ， When k=1, 2..., the moiré fringe image is clearest. This is called the Talbot distance; the depth of focus is defined by the brightness field width, and the different wavelengths of the combined light spectrum are within the Talbot distance. The integral on the surface extends the depth of focus, and the extended depth of focus is: ， In the formula, N is the multiple of the extended Tabor distance substrate alignment mark grating.

8. The method for aligning and leveling multi-wavelength stacked grating array markers according to claim 7, characterized in that, Step four is as follows: The recorded moiré interference fringe signal is converted into a digital image for fine alignment. The effective range is cropped by image preprocessing algorithm, and the phase is analyzed by Fourier transform. The phase difference of the moiré interference fringes is calculated, thereby adjusting the relative positional relationship between the mask alignment mark grating and the substrate alignment mark grating. When the mask alignment mark grating and the substrate alignment mark grating are misaligned At that time, the expression for the complex amplitude of the moiré fringes is: ， ， in , The grating frequency of the mask alignment mark grating and the substrate alignment mark grating; The complex amplitude distribution of moiré fringes formed by superimposing the gratings on the mask alignment marks and the corresponding gratings on the substrate alignment marks; The complex amplitude distribution of moiré fringes formed by superimposing another grating for the mask alignment mark with the corresponding grating for the substrate alignment mark; The period is and The grating co-formation period is Calculate the phase difference between the two gratings that form the moiré fringes: ， ， ， Calculate the offset between the mask and the substrate alignment mark grating: 。

Images