Mask and wafer leveling method

Abstract

The invention relates to a mask and wafer leveling method, which comprises the following steps of: vertically irradiating a leveling grating positioned on the surface of a mask by using a light source to generate a square moire fringe pattern; determining a first observation area in the lower side part of the right side area, and calculating a fringe rotation angle and an actual fringe frequency by extracting a moire fringe phase of the first observation area; calculating the angle offset of the wafer in the space when the cross section inclination and the longitudinal section inclination respectively occur relative to the mask; and performing feedback adjustment according to the measured angle offset. By measuring the phase change of the first observation area in the square Moire fringe pattern and then through formula conversion, the offset of the wafer in the space when the cross section inclination and the longitudinal section inclination respectively occur relative to the mask can be accurately calculated. The problem that an existing mask and wafer leveling method cannot achieve high-precision detection of the multi-interface inclination angle through single-point measurement is solved, and the measurement efficiency and the measurement precision are improved.

Description

Technical Field

[0001] The present application relates to the field of photolithography technology, and in particular to a method for leveling a mask and a wafer. Background Art

[0002] Mask-wafer leveling is a key step in the photolithography process. Its core is to adjust the gap consistency between the wafer and the mask to ensure the accurate transfer of the pattern. The leveling accuracy directly affects the accuracy of feature size, pattern quality and production yield, especially in high-resolution advanced processes, where the leveling accuracy requirements are particularly stringent.

[0003] The traditional multi-point gap measurement method achieves leveling by measuring the gap at multiple points and calculating the tilt state of the wafer. However, this method has a complex system, low measurement efficiency, and insufficient real-time performance. It can only indirectly obtain the tilt state of the wafer and is difficult to achieve high-precision detection of multi-interface tilt angles. This has become the main bottleneck restricting the accuracy of lithography leveling. Although the zero-difference and heterodyne interference methods have a certain sensitivity, their accuracy is limited and they are easily affected by environmental interference. In addition, it is difficult to compensate for the tilt angle between the wafer and the mask through single-point measurement. There is currently no effective solution to the problem that the existing mask-wafer leveling method cannot achieve high-precision detection of multi-interface tilt angles through single-point measurement. Summary of the invention

[0004] The present invention provides a mask and wafer leveling method to solve the problem that the existing mask and wafer leveling method cannot achieve high-precision detection of multi-interface tilt angles through single-point measurement.

[0005] In this embodiment, a method for leveling a mask and a wafer is provided, comprising:

[0006] A light source is used to vertically illuminate a leveling grating, the leveling grating is located on the mask surface, and is divided into four quadrants according to quadrants, each quadrant includes a plurality of L-shaped light-shielding lines with equal spacing, and the two sides of each L-shaped light-shielding line are equal in length and are respectively perpendicular to the boundaries of two quadrants, the spacing of the L-shaped light-shielding lines in the first quadrant and the third quadrant is a first spacing, and the spacing of the L-shaped light-shielding lines in the second quadrant and the fourth quadrant is a second spacing, the first spacing is greater than the second spacing, and the duty ratio of the plurality of L-shaped light-shielding lines in each quadrant is 1 / 2, and the incident light of the light source is transmitted through the first quadrant and the third quadrant of the leveling grating and is reflected by the wafer to generate a first diffraction beam, and is transmitted through the second quadrant and the fourth quadrant of the leveling grating and is reflected by the wafer to generate a second diffraction beam, and the first diffraction beam and the second diffraction beam interfere with each other and generate a square moiré fringe pattern;

[0007] The square moiré fringe pattern is divided by diagonal lines to obtain four isosceles triangle regions, and each region is divided into two parts by its own perpendicular midline;

[0008] Determine a first observation area in the lower part of the area on the right, and determine a fringe rotation angle and an actual fringe frequency of the first observation area;

[0009] The first angle offset ε when the wafer is tilted in the longitudinal section relative to the mask in space is determined by the ideal fringe frequency and the actual fringe frequency of the first observation area. x , according to the first conversion formula, determine the second angle offset ε when the wafer is tilted in space relative to the mask cross section y , the first conversion formula is:

[0010]

[0011] Among them, θ 1 is the first diffraction angle, θ 2 is the second diffraction angle, θ 1 is the stripe rotation angle;

[0012] When the wafer and the mask are parallel to each other, the angle between the incident light of the light source and the first diffracted light beam is the first diffraction angle, the angle between the incident light of the light source and the second diffracted light beam is the second diffraction angle, and the fringe frequency of the square moiré fringe pattern is the ideal fringe frequency;

[0013] According to ε x and ε y Level the wafer and mask.

[0014] In some embodiments, the first pitch is 1.1 times the second pitch.

[0015] In some of the embodiments, the first diffraction angle, the second diffraction angle and the ideal fringe frequency are determined by an angle formula, and the angle formula is:

[0016] θ 1 =sin -1 (λ / P 1 )

[0017] θ 2 =sin -1 (λ / P 2 )

[0018] f 0 =(sinθ 1 -sinθ 2 ) / λ=1 / P 1 -1 / P 2

[0019] Where λ is the wavelength of the incident light, P 2 is the first spacing, P 1 is the second spacing, θ 1 is the first diffraction angle, θ 2 is the second diffraction angle, f 0 is the ideal fringe frequency.

[0020] In some embodiments, determining the fringe rotation angle and the actual fringe frequency of the first observation area includes:

[0021] Determine the phases of three non-collinear phase points A, B, and C in the first observation area and calculate the phase difference between phase points A and B And the phase difference between phase points A and C

[0022] according to and Determine the fringe rotation angle and actual fringe frequency of the first observation area.

[0023] In some of the embodiments, according to and Determining the fringe rotation angle and the actual fringe frequency of the first observation area includes:

[0024] The fringe rotation angle and actual fringe frequency of the first observation area are determined by the phase formula, which is:

[0025]

[0026]

[0027] in, and are the phase differences between A and B, A and C, θ l and f l are the fringe rotation angle and actual fringe frequency of the first observation area respectively, and points is the number of phase points.

[0028] In some embodiments, a first angular offset ε when the wafer is tilted in a longitudinal section relative to the mask in space is determined. x include:

[0029] Determine the first angle offset ε when the wafer is tilted in the longitudinal section relative to the mask in space according to the first frequency formula x , the first frequency formula is:

[0030] f l =f 0 +2ε x cosθ 1 / λ

[0031] Among them, f 0 is the ideal fringe frequency, f l is the actual fringe frequency, and λ is the wavelength of the incident light.

[0032] In some of the embodiments, the phase formula is obtained by unwrapping the Moire fringe intensity formula of the first observation area.

[0033] In some embodiments, the formula for the intensity of the moiré fringe in the first observation area is:

[0034]

[0035] Among them, I 2 is the Moire fringe intensity of the first observation area, I B1 ,I B2 are the intensities of the first diffracted beam and the second diffracted beam, respectively, is the initial phase difference.

[0036] In some of the embodiments, the method for collecting the generated square moiré fringe pattern is to collect it in real time through a CCD camera.

[0037] In some of the embodiments, according to ε x and ε y Leveling the wafer and mask involves moving the ε x and ε y Feedback is input to the leveling stage of the lithography machine, and the leveling stage is used to level the wafer and mask.

[0038] Compared with the related art, the present invention has the following beneficial effects:

[0039] The invention provides a mask and wafer leveling method, wherein a light source is used to vertically illuminate a leveling grating located on a mask surface, and incident light from the light source passes through each quadrant of the leveling grating to generate two groups of intersecting diffraction light beams, and the two groups of light beams respectively generate interference effects with grating periodic structures in horizontal and vertical directions, and finally form a square interference field and generate a square moiré fringe pattern. Moreover, due to the structural particularity of the square moiré fringe pattern, the interference effects of four areas in the pattern are intertwined with each other, and the interference fringes displayed can not only respond to the lateral tilt of the wafer, but also respond to the longitudinal tilt of the wafer. Therefore, it is only necessary to measure the phase change of any area in the square moiré fringe pattern, and then accurately calculate the angular offset of the wafer in space when the cross-sectional tilt and the longitudinal section tilt occur respectively relative to the mask through formula conversion, thereby solving the problem that the existing mask and wafer leveling method cannot realize high-precision detection of multi-interface tilt angles through single-point measurement, and improving the measurement efficiency and measurement accuracy.

[0040] Details of one or more embodiments of the present application are set forth in the following drawings and description to make other features, objects, and advantages of the present application more readily apparent. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is a schematic diagram of the longitudinal cross-section structure of the mask and wafer leveling system;

[0042] Figure 2 It is a schematic diagram of the structure of the leveling grating;

[0043] Figure 3 It is the center-symmetrical square moiré fringe pattern when leveled;

[0044] Figure 4 It is the moiré fringe pattern when the wafer is tilted in the longitudinal section;

[0045] Figure 5 is a schematic diagram of the cross-sectional structure of the mask and wafer leveling system;

[0046] Figure 6 It is the moiré fringe pattern when the wafer is tilted in cross section;

[0047] Figure 7 It is a flowchart of the specific steps for leveling the mask and wafer. DETAILED DESCRIPTION

[0048] In order to more clearly understand the purpose, technical solutions and advantages of the present application, the present application is described and illustrated below in conjunction with the accompanying drawings and embodiments.

[0049] In this embodiment, a method for leveling a mask and a wafer is provided. Figure 7 As shown, the method comprises steps S1, S2, S3, S4 and S5.

[0050] Step S1, refer to Figure 1 As shown, the leveling grating is illuminated vertically with a light source. The leveling grating is located on the mask surface and is divided into four quadrants according to the quadrants. Figure 2As shown, each quadrant part includes a plurality of L-shaped shading lines with equal spacing, and the two sides of each L-shaped shading line are equal in length and are respectively perpendicular to the boundaries of the two quadrants. The spacing of the L-shaped shading lines in the first quadrant part and the third quadrant part is a first spacing, and the spacing of the L-shaped shading lines in the second quadrant part and the fourth quadrant part is a second spacing, the first spacing is greater than the second spacing, and the duty ratio of the plurality of L-shaped shading lines in each quadrant part is 1 / 2. The incident light of the light source passes through the first quadrant part and the third quadrant part of the leveling grating and is reflected by the wafer to generate a first diffraction beam, and passes through the second quadrant part and the fourth quadrant part of the leveling grating and is reflected by the wafer to generate a second diffraction beam. The first diffraction beam and the second diffraction beam interfere with each other and generate a square moiré fringe pattern.

[0051] In this embodiment, the incident light of the light source passes through each quadrant of the leveling grating to generate two groups of intersecting diffracted light beams, and these two groups of light beams respectively produce interference effects with the grating periodic structures in the horizontal and vertical directions, and finally form a square interference field and generate a square moiré fringe pattern. Furthermore, making the grating duty cycle in the two grating marks 1 / 2 can maximize the light intensity contrast of the moiré fringes, improve the detection signal-to-noise ratio, thereby enhancing the recognizability of the moiré fringes, and also help generate a diffracted light field, ensuring the generation of a high-quality moiré fringe interference image, and then more accurately measuring the tilt angle between the mask and the wafer, thereby improving the leveling accuracy of the mask and the wafer.

[0052] Further, in this embodiment, the first spacing is 1.1 times the second spacing. 2 , the second spacing is P 1 , that is, P 2 =1.1P 1 , due to the moiré fringe period P m =(P 2 P 1 ) / (P 2 -P 1 ), when the grating period satisfies P 2 =1.1P 1 When the denominator (P 2 -P 1 ), which can significantly enhance the displacement amplification effect of the moiré fringes and improve the leveling accuracy of the mask and wafer. At the same time, because the period P of the moiré fringes m Significantly larger than a single grating period, a tiny tilt can cause a noticeable fringe displacement, thus improving the measurement resolution.

[0053] Exemplarily, in this embodiment, the method for collecting the generated square moiré fringe image is to collect it in real time through a CCD camera. The CCD camera has the characteristics of high resolution and high sensitivity, and can accurately capture the details of the moiré fringe. The phase change of the moiré fringe is closely related to the displacement or deformation of the object being measured, and the leveling stage is driven by a real-time feedback mechanism, which can quickly respond to the tilt change of the wafer and meet the high requirements for real-time leveling in the lithography process.

[0054] Reference Figure 3 As shown, in an ideal state, when the mask and the wafer are parallel to each other, the fringes in the square moiré fringe pattern generated by them will not be misaligned. When the wafer and the mask are parallel to each other, the angle between the incident light of the light source and the first diffraction beam is the first diffraction angle, the angle between the incident light of the light source and the second diffraction beam is the second diffraction angle, and the fringe frequency of the square moiré fringe pattern is the ideal fringe frequency. Among them, the first diffraction angle, the second diffraction angle and the ideal fringe frequency are determined by the angle formula.

[0055] Specifically, in this embodiment, the angle formula is:

[0056] θ 1 =sin -1 (λ / P 1 )

[0057] θ 2 =sin -1 (λ / P 2 )

[0058] f 0 =(sinθ 1 -sinθ 2 ) / λ=1 / P 1 -1 / P 2

[0059] Where λ is the wavelength of the incident light, P 2 is the first spacing, P 1 is the second spacing, θ 1 is the first diffraction angle, θ 2 is the second diffraction angle, f 0 is the ideal fringe frequency.

[0060] Step S2, the square moiré fringe pattern is divided by diagonal lines to obtain four isosceles triangle regions, each region is divided into two parts by its own perpendicular midline as a dividing line. The four regions are the upper region (I 3 ), lower area (I 4 ), Left Area(I 1 ) and the right area (I 2 ).

[0061] Exemplarily, due to the structural characteristics of the square moiré fringe pattern, refer to Figure 1 and Figure 4 As shown, the changes in the moiré fringes in the left and right areas of the square moiré fringe image correspond to the situation where the wafer is tilted in the longitudinal section relative to the mask in space. At the same time, the changes in the moiré fringes in the upper and lower areas of the square moiré fringe image also correspond to the situation where the wafer is tilted in the cross section relative to the mask in space, and vice versa.

[0062] Step S3, determining a first observation area in the lower part of the right area, and determining a fringe rotation angle and an actual fringe frequency of the first observation area.

[0063] In this embodiment, determining the fringe rotation angle and the actual fringe frequency of the first observation area includes: determining the phases of three non-collinear phase points A, B, and C in the first observation area and calculating the phase difference between phase points A and B. And the phase difference between phase points A and C according to and Determine the fringe rotation angle and actual fringe frequency of the first observation area. and Determining the fringe rotation angle and the actual fringe frequency of the first observation area includes: determining the fringe rotation angle and the actual fringe frequency of the first observation area by a phase formula.

[0064] Specifically, after determining the first observation area, a continuous phase diagram of the first observation area is obtained, referring to Figure 5 and Figure 6 As shown, Figure 6 (a) is the fringe pattern when the wafer is tilted; Figure 6 (b) is the local fringe pattern corresponding to the lower part of the right area. Figure 6 (c) is an enlarged view of the stripes in (b). Figure 6 (d) Yes Figure 6 (c) The corresponding continuous phase diagram, the phase points of the continuous phase diagram include A, B and C, and the phase differences between A and B, A and C are respectively extracted and substituted into the phase formula to calculate the fringe rotation angle and the actual fringe frequency of the first observation area. In this embodiment, the first observation area is the right area (I 2 ), in other embodiments, the first observation area may also be other areas (I 1 ,I 3 ,I 4 ) on either side of the

[0065] Specifically, in this embodiment, the phase formula is:

[0066]

[0067] in, and are the phase differences between A and B, A and C, θ l and f l The fringe rotation angle and actual fringe frequency of the lower part of the right area are shown respectively, and points is the number of phase points.

[0068] Furthermore, the phase formula is obtained by unwrapping the Moire fringe intensity formula of the lower part of the right area. Figure 1 and Figure 5 As shown, when the wafer is tilted at a certain angle ε in the longitudinal section and cross section relative to the mask in space x and ε y When the reflected beam B 1 Corresponding to the deflection of 2ε in the two sections x and 2ε y Form B 1 ', the interference angle becomes θ 1 +2ε x and θ 2 +2ε y , the intensity field of the moiré fringe is modulated, and the moiré fringe intensity formula of the lower part of the right area can be rewritten as:

[0069]

[0070] Among them, I 2 is the moiré fringe intensity of the lower part of the right area, I B1 ,I B2 are the intensities of the first diffracted beam and the second diffracted beam, respectively, The beam intensity and initial phase difference can be directly measured and extracted by the machine.

[0071] Step S4, determining a first angle offset ε when the wafer is tilted in the longitudinal section relative to the mask in space by using the ideal fringe frequency and the actual fringe frequency of the first observation area. x , according to the first conversion formula, determine the second angle offset ε when the wafer is tilted in space relative to the mask cross section y .

[0072] Specifically, the actual fringe frequency, the ideal fringe frequency, and the first diffraction angle of the first observation area are substituted into the first frequency formula to calculate the first angle offset ε when the wafer is tilted in the longitudinal section relative to the mask in space. x , the first angle offset ε x , the first diffraction angle, the second diffraction angle and the fringe rotation angle are substituted into the first conversion formula to calculate the second angle offset ε when the wafer is tilted relative to the mask in space. y .

[0073] Furthermore, in this embodiment, the first frequency formula is:

[0074] f l =f 0 +2ε x1 cosθ 1 / λ

[0075] Among them, f 0 is the ideal fringe frequency, f l is the actual fringe frequency, and λ is the wavelength of the incident light.

[0076] The first conversion formula is:

[0077]

[0078] Among them, θ 1 is the first diffraction angle, θ 2 is the second diffraction angle, θ l is the fringe rotation angle, ε y An offset is selected for a second angle at which the wafer is tilted in cross section relative to the mask in space.

[0079] Step S5: according to the first angle offset ε x and the second angular offset ε y Level the wafer and mask.

[0080] Among them, ε can be calculated x and ε y Directly input the leveling stage of the lithography machine for feedback, and the leveling stage will level the wafer and mask. x and ε y Verification is carried out, and after verification, it is input into the leveling stage of the lithography machine for feedback, and the leveling stage is used to level the wafer and mask.

[0081] Specifically, the upper part of the right area is determined as the second observation area. Similarly, the phases of the three non-collinear phase points D, E, and F in the second observation area are determined and the phase difference between the phase points D and E is calculated. And the phase difference between phase points D and F Will and Substitute into the second phase formula to find the fringe rotation angle θ of the second observation area u and the actual fringe frequency f u , the second phase formula is:

[0082]

[0083] The second diffraction angle θ 2and the ideal fringe frequency f 0 Substitute into the second frequency formula to find the third angle offset ε x ′, the second frequency formula is:

[0084] f u =f 0 -2ε x ′cosθ 2 / λ

[0085] The first diffraction angle θ 1 , the second diffraction angle θ 2 and ε x Substitute into the second conversion formula to find the fourth angle offset ε of the upper part of the right area y ', the second conversion formula is:

[0086]

[0087] ε x and ε y As the first set of data, ε x ′ and ε y ′ is used as the second set of data. The two sets of data are compared to verify the accuracy of the measurement. If there is no error or the error is small (this can be judged by setting a threshold), it means that the measurement data is accurate. If the error is large, it means that the measurement data is inaccurate. The two sets of data are discarded and remeasured.

[0088] Furthermore, if the error between the two sets of data is less than the threshold, ε x and ε y Feedback is input to the leveling stage of the lithography machine, and the leveling stage is used to level the wafer and the mask.

[0089] It should be noted that this embodiment calculates the errors between the mask and the wafer in two directions based on the right area of ​​the square moiré fringe pattern. Correspondingly, the errors between the mask and the wafer in two directions can be obtained by the same calculation method based on other areas. For example, the first angle offset ε is calculated based on the left part of the upper area. x and the second angular offset ε y , and the third angle offset ε is calculated based on the right part of the upper area x ′ and the fourth angle offset ε y ′, and finally the first angle offset ε that passes the verification x and the second angular offset ε y Feedback is input to the leveling stage of the lithography machine, and the leveling stage is used to level the wafer and the mask.

[0090] In summary, a method for leveling a mask and a wafer is provided in this embodiment, wherein a light source is used to vertically illuminate a leveling grating located on the surface of the mask, and the incident light of the light source passes through each quadrant of the leveling grating to generate two groups of intersecting diffraction light beams, and the two groups of light beams respectively produce interference effects with the grating periodic structures in the horizontal and vertical directions, and finally form a square interference field and generate a square moiré fringe pattern. Moreover, due to the structural particularity of the square moiré fringe pattern, the interference effects of the four areas in the figure are intertwined with each other, and the interference fringes displayed can not only respond to the lateral tilt of the wafer, but also respond to the longitudinal tilt of the wafer. Therefore, it is only necessary to measure the phase change of any area in the square moiré fringe pattern, and then the angular offset of the wafer in space relative to the mask when the cross-sectional tilt and the longitudinal section tilt occur respectively can be accurately calculated through formula conversion, thereby solving the problem that the existing mask and wafer leveling method cannot achieve high-precision detection of multi-interface tilt angles through single-point measurement, thereby improving measurement efficiency and measurement accuracy.

[0091] It should be understood that the specific embodiments described herein are only used to explain the application, rather than to limit it. Based on the embodiments provided in this application, all other embodiments obtained by ordinary technicians in this field without creative work are within the protection scope of this application.

[0092] Obviously, the drawings are only some examples or embodiments of the present application. For ordinary technicians in the field, the present application can also be applied to other similar situations based on these drawings without creative work. In addition, it is understandable that although the work done in this development process may be complicated and lengthy, for ordinary technicians in the field, certain changes in design, manufacturing or production based on the technical content disclosed in this application are only conventional technical means and should not be regarded as insufficient content disclosed in this application.

Claims

1. A method for leveling a mask and a wafer, characterized in that: include: A light source is used to vertically illuminate a leveling grating, the leveling grating is located on the mask surface, and is divided into four quadrants according to quadrants, each quadrant includes a plurality of L-shaped light-shielding lines with equal spacing, and the two sides of each L-shaped light-shielding line are equal in length and are respectively perpendicular to the boundaries of two quadrants, the spacing of the L-shaped light-shielding lines in the first quadrant and the third quadrant is a first spacing, and the spacing of the L-shaped light-shielding lines in the second quadrant and the fourth quadrant is a second spacing, the first spacing is greater than the second spacing, and the duty ratio of the plurality of L-shaped light-shielding lines in each quadrant is 1 / 2, and the incident light of the light source is transmitted through the first quadrant and the third quadrant of the leveling grating and is reflected by the wafer to generate a first diffraction beam, and is transmitted through the second quadrant and the fourth quadrant of the leveling grating and is reflected by the wafer to generate a second diffraction beam, and the first diffraction beam and the second diffraction beam interfere with each other and generate a square moiré fringe pattern; The square moiré fringe pattern is divided by diagonal lines to obtain four isosceles triangle regions, and each region is divided into two parts by its own perpendicular midline; Determine a first observation area in the lower part of the area on the right, and determine a fringe rotation angle and an actual fringe frequency of the first observation area; The first angle offset ε when the wafer is tilted in the longitudinal section relative to the mask in space is determined by the ideal fringe frequency and the actual fringe frequency of the first observation area. x , according to the first conversion formula, determine the second angle offset ε when the wafer is tilted in space relative to the mask cross section y , the first conversion formula is: Wherein, θ1 is the first diffraction angle, θ2 is the second diffraction angle, and θ1 is the fringe rotation angle; When the wafer and the mask are parallel to each other, the angle between the incident light of the light source and the first diffracted light beam is the first diffraction angle, the angle between the incident light of the light source and the second diffracted light beam is the second diffraction angle, and the fringe frequency of the square moiré fringe pattern is the ideal fringe frequency; According to ε x and ε y Level the wafer and mask.

2. The method for leveling a mask and a wafer according to claim 1, characterized in that: The first spacing is 1.1 times the second spacing.

3. The method for leveling a mask and a wafer according to claim 1, characterized in that: The first diffraction angle, the second diffraction angle and the ideal fringe frequency are determined by the angle formula, which is: θ1=sin -1 (l / P1) θ2=sin -1 (l / P2) f0=(sinθ1-sinθ2) / λ=1 / P1-1 / P2 Wherein, λ is the wavelength of the incident light, P2 is the first pitch, P1 is the second pitch, θ1 is the first diffraction angle, θ2 is the second diffraction angle, and f0 is the ideal fringe frequency.

4. The method for leveling a mask and a wafer according to claim 1, characterized in that: Determining the fringe rotation angle and the actual fringe frequency of the first observation area includes: Determine the phases of three non-collinear phase points A, B, and C in the first observation area and calculate the phase difference between phase points A and B And the phase difference between phase points A and C according to and Determine the fringe rotation angle and actual fringe frequency of the first observation area.

5. The method for leveling a mask and a wafer according to claim 4, characterized in that: according to and Determining the fringe rotation angle and the actual fringe frequency of the first observation area includes: The fringe rotation angle and actual fringe frequency of the first observation area are determined by the phase formula, which is: Among them, θ1 and f1 are the fringe rotation angle and actual fringe frequency of the first observation area, respectively, and points is the number of phase points.

6. The method for leveling a mask and a wafer according to claim 1, characterized in that: Determine the first angle offset ε when the wafer is tilted in the longitudinal section relative to the mask in space x include: Determine the first angle offset ε when the wafer is tilted in the longitudinal section relative to the mask in space according to the first frequency formula x , the first frequency formula is: f1=f0+2ε x cosθ1 / λ Among them, f0 is the ideal fringe frequency, f1 is the actual fringe frequency, and λ is the wavelength of the incident light.

7. The method for leveling a mask and a wafer according to claim 5, characterized in that: The phase formula is obtained by unwrapping the Moire fringe intensity formula of the first observation area.

8. The method for leveling a mask and a wafer according to claim 7, characterized in that: The formula for the Moire fringe intensity in the first observation area is: Where I2 is the Moire fringe intensity of the first observation area, I B1 ,I B2 are the intensities of the first diffracted beam and the second diffracted beam, respectively, is the initial phase difference.

9. The method for leveling a mask and a wafer according to claim 1, characterized in that: The method for collecting the generated square moiré fringe pattern is to collect it in real time through a CCD camera.

10. The method for leveling a mask and a wafer according to claim 1, characterized in that: According to ε x and ε y Leveling the wafer and mask involves moving the ε x and ε y Feedback is input to the leveling stage of the lithography machine, and the leveling stage is used to level the wafer and the mask.

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