A method for leveling a mask and a wafer

Abstract

The application relates to a mask and wafer leveling method, wherein the method comprises the following steps: vertically irradiating a leveling grating on a mask surface with a light source to generate a square moire fringe pattern; determining a first observation area in the lower part of the right region, calculating a fringe rotation angle and an actual fringe frequency by extracting the moire fringe phase of the first observation area; calculating the angle offset amount of the wafer in space relative to the mask when cross-section tilting and longitudinal section tilting occur respectively; and performing feedback adjustment according to the measured angle offset amount. The phase change of the first observation area in the square moire fringe pattern is measured, and then the offset amount of the wafer in space relative to the mask when cross-section tilting and longitudinal section tilting occur respectively can be accurately calculated through formula conversion, thereby solving the problem that the existing mask and wafer leveling method cannot realize high-precision detection of multi-interface tilting angles through single-point measurement, and improving the measurement efficiency and measurement precision.

Description

TECHNICAL FIELD

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

[0002] Mask-wafer leveling is a key link in the photolithography process, and its core is to adjust the gap consistency between the wafer and the mask, so as 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 the advanced process of high resolution, the accuracy requirement of leveling is particularly harsh.

[0003] The traditional multi-point gap measurement method realizes leveling by measuring the gap at multiple points and calculating the tilt state of the wafer, but this method is complex, low in measurement efficiency and real-time, and can only indirectly obtain the tilt state of the wafer, which is difficult to realize high-precision detection of multi-interface tilt angle, and has become the main bottleneck restricting the photolithography leveling accuracy. Although the homodyne and heterodyne interference methods have certain sensitivity, the precision is limited and easily affected by the environment, and it is difficult to compensate for the tilt angle between the wafer and the mask through single-point measurement. In view of the problem that the existing mask and wafer leveling method cannot realize high-precision detection of multi-interface tilt angle through single-point measurement, there is no effective solution at present. SUMMARY

[0004] A mask and wafer leveling method is provided in the present application to solve the problem that the existing mask and wafer leveling method cannot realize high-precision detection of multi-interface tilt angle through single-point measurement.

[0005] A mask and wafer leveling method is provided in the present embodiment, comprising:

[0006] The leveling grating is vertically irradiated by a light source, the leveling grating is located on the surface of the mask, and it is divided into four quadrant parts according to the quadrant, each quadrant part includes multiple L-shaped light blocking lines at equal intervals, the two sides of each L-shaped light blocking line are equal in length and perpendicular to two quadrant boundaries respectively, the interval of the L-shaped light blocking lines in the first and third quadrant parts is the first interval, and the interval of the L-shaped light blocking lines in the second and fourth quadrant parts is the second interval, the first interval is greater than the second interval, and the duty cycle of the multiple L-shaped light blocking lines in each quadrant part is 1 / 2, the incident light of the light source transmits through the first and third quadrant parts of the leveling grating and generates a first diffracted light beam after being reflected by the wafer, and the incident light of the light source transmits through the second and fourth quadrant parts of the leveling grating and generates a second diffracted light beam after being reflected by the wafer, the first and second diffracted light beams interfere with each other and generate a square Moire 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 median.

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

[0009] The first angle offset ε when the wafer is tilted relative to the mask in the longitudinal section 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, the second angle offset ε when the wafer is tilted relative to the mask in space is determined y , the first conversion formula is:

[0010]

[0011] Among them, θ1 is the first diffraction angle, θ2 is the second diffraction angle, θ l 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 beam is the first diffraction angle, the angle between the incident light of the light source and the second diffracted 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 spacing is 1.1 times the second spacing.

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

[0016] θ1=sin -1 (λ / P1)

[0017] θ2=sin -1 (λ / P2)

[0018] f0=(sinθ1-sinθ2) / λ=1 / P1-1 / P2

[0019] 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.

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

[0021] determining phases of three non-collinear phase points A, B, C in the first observation area and calculating a phase difference between phase points A and B and a phase difference between phase points A and C

[0022] According to and determining a fringe rotation angle and an actual fringe frequency of the first observation area.

[0023] In some embodiments thereof, determining a fringe rotation angle and an actual fringe frequency of the first observation area according to and comprises:

[0024] determining a fringe rotation angle and an actual fringe frequency of the first observation area by a phase formula, the phase formula being:

[0025]

[0026]

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

[0028] In some embodiments thereof, determining a first angular displacement ε x of the wafer in space relative to the mask when a longitudinal cross-section tilt occurs comprises:

[0029] determining a first angular displacement ε x of the wafer in space relative to the mask when a longitudinal cross-section tilt occurs according to a first frequency formula, the first frequency formula being:

[0030] f l = f0+ 2ε x cos θ1 / λ

[0031] wherein f0is an ideal fringe frequency, f l is an actual fringe frequency, and λ is a wavelength of the incident light.

[0032] In some embodiments thereof, the phase formula is unwrapped from a Moiré fringe intensity formula of the first observation area.

[0033] In some embodiments thereof, the Moiré fringe intensity formula of the first observation area is:

[0034]

[0035] wherein I2 is the intensity of the Moire fringe of the first observation area, I B1 , I B2 are the intensity of the first diffraction beam and the second diffraction beam respectively, is the initial phase difference.

[0036] In some embodiments, the method for collecting the generated square Moire fringe pattern is real-time collection by a CCD camera.

[0037] In some embodiments, according to ε x and ε y , the leveling of the wafer and the mask includes inputting ε x and ε y to the leveling displacement table of the photolithography machine for feedback, and leveling the wafer and the mask by the leveling displacement table.

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

[0039] The present application provides a leveling method for a mask and a wafer, which vertically irradiates a leveling grating on the surface of the mask with a light source. The incident light of the light source transmits through each quadrant of the leveling grating to generate two groups of intersecting diffraction beams. The two groups of beams respectively generate interference effects with the grating period structure in the horizontal and vertical directions, and finally form a square interference field and generate a square Moire fringe pattern. Due to the special structure of the square Moire fringe pattern, the interference effects of the four regions in the pattern are interwoven with each other, and the interference fringes displayed can respond not only to the lateral tilt of the wafer, but also to the longitudinal tilt of the wafer. Therefore, only the phase change of any region in the square Moire fringe pattern needs to be measured, and then the angle offset amount of the wafer in space relative to the mask when the cross-section tilt and the longitudinal tilt occur is accurately calculated through formula conversion. The problem that the existing leveling method for the mask and the wafer cannot realize high-precision detection of the tilt angle of multiple interfaces through single-point measurement is solved, and the measurement efficiency and accuracy are improved.

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

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

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

[0043] Figure 3 is a center-symmetric square Moire fringe pattern during leveling;

[0044] Figure 4 is a Moiré fringe diagram of the wafer when the wafer is tilted in the longitudinal cross section;

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

[0046] Figure 6 is a Moiré fringe diagram of the wafer when the wafer is tilted in the cross section;

[0047] Figure 7 is a specific step flow chart of mask and wafer leveling. 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 explained below in conjunction with the drawings and examples.

[0049] In the present embodiment, a mask and wafer leveling method is provided, as shown in Figure 7 the method steps include steps S1, S2, S3, S4 and S5.

[0050] Step S1, as shown in Figure 1 a light source is used to vertically irradiate a leveling grating, the leveling grating is located on the surface of the mask, and it is divided into four quadrant parts according to the quadrants, as shown in Figure 2 each quadrant part includes a plurality of L-shaped light blocking lines at equal intervals, each L-shaped light blocking line has two equal sides that are perpendicular to two quadrant boundaries, the interval of the L-shaped light blocking lines in the first and third quadrant parts is a first interval, and the interval of the L-shaped light blocking lines in the second and fourth quadrant parts is a second interval, the first interval is greater than the second interval, and the duty cycle of the plurality of L-shaped light blocking lines in each quadrant part is 1 / 2, the incident light of the light source passes through the first and third quadrant parts of the leveling grating, is reflected by the wafer to generate a first diffracted light beam, and passes through the second and fourth quadrant parts of the leveling grating, is reflected by the wafer to generate a second diffracted light beam, the first and second diffracted light beams interfere with each other to generate a square Moiré fringe diagram.

[0051] In the present embodiment, the incident light of the light source passing through each quadrant of the leveling grating produces two groups of intersecting diffracted light beams, the two groups of light beams produce interference effects with the grating period structure in the horizontal and vertical directions, respectively, to finally form a square interference field and generate a square Moiré fringe diagram. Further, the duty cycle of the grating in the two grating marks is 1 / 2, which can maximize the light intensity contrast of the Moiré fringe, improve the signal-to-noise ratio of the detection, thereby enhancing the distinguishability of the Moiré fringe, also helping to generate the diffracted light field, ensuring the generation of high-quality Moiré fringe interference images, and further more accurately measuring the tilt angle between the mask and the wafer, thereby improving the leveling precision of the mask and the wafer.

[0052] Further, in the embodiment, the first interval is 1.1 times of the second interval. The first interval is P2, and the second interval is P1, that is, P2 = 1.1P1. Since the Moiré fringe period P m = (P2P1) / (P2-P1), when the grating period satisfies P2 = 1.1P1, the denominator (P2-P1) is reduced, which can significantly enhance the displacement amplification effect of the Moiré fringe, and improve the leveling accuracy of the mask and the wafer. At the same time, because the period P m of the Moiré fringe is significantly larger than the single grating period, a slight tilt can cause a significant fringe displacement, thereby improving the measurement resolution.

[0053] Exemplarily, in the embodiment, the method for collecting the generated square Moiré fringe image is real-time collection by 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 measured object, and the leveling displacement table is driven through a real-time feedback mechanism, which can quickly respond to the tilt change of the wafer and meet the high requirements of real-time leveling in the photolithography process.

[0054] Referring to Figure 3 , in an ideal state, when the mask and the wafer are parallel to each other, the fringes in the square Moiré fringe image generated thereby will not be misaligned. When the wafer and the mask are parallel to each other, the included angle between the incident light of the light source and the first diffracted beam is the first diffraction angle, the included angle between the incident light of the light source and the second diffracted beam is the second diffraction angle, and the fringe frequency of the square Moiré fringe image is the ideal fringe frequency. The first diffraction angle, the second diffraction angle and the ideal fringe frequency are determined by an angle formula.

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

[0056] θ1 = sin -1 (λ / P1)

[0057] θ2 = sin -1 (λ / P2)

[0058] f0 = (sinθ1-sinθ2) / λ = 1 / P1-1 / P2

[0059] Wherein, λ is the wavelength of the incident light, P2 is the first interval, P1 is the second interval, θ1 is the first diffraction angle, θ2 is the second diffraction angle, and f0 is the ideal fringe frequency.

[0060] Step S2, the square Moire fringe pattern is divided into four isosceles triangle regions by diagonal lines, each region is divided into two parts by the median line of the region. The four regions are upper region (I3), lower region (I4), left region (I1) and right region (I2).

[0061] As shown in the square Moire fringe pattern, the change of Moire fringe in the left region and the right region corresponds to the case that the wafer is tilted relative to the mask in the longitudinal cross section in space, while the change of Moire fringe in the upper region and the lower region also corresponds to the case that the wafer is tilted relative to the mask in the horizontal cross section in space, and vice versa. Figure 1 and Figure 4 As shown in the square Moire fringe pattern, the change of Moire fringe in the left region and the right region corresponds to the case that the wafer is tilted relative to the mask in the longitudinal cross section in space, while the change of Moire fringe in the upper region and the lower region also corresponds to the case that the wafer is tilted relative to the mask in the horizontal cross section in space, and vice versa.

[0062] Step S3, the first observation area is determined in the lower side part of the right region, and the fringe rotation angle and the actual fringe frequency of the first observation area are determined.

[0063] In the embodiment, the fringe rotation angle and the actual fringe frequency of the first observation area are determined by 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 the fringe rotation angle and the actual fringe frequency of the first observation area are determined. Further, according to and the fringe rotation angle and the actual fringe frequency of the first observation area are determined by determining the fringe rotation angle and the actual fringe frequency of the first observation area through the phase formula.

[0064] Specifically, after the first observation area is determined, the continuous phase pattern of the first observation area is obtained, as shown in Figure 5 and Figure 6 wherein Figure 6 (a) is the fringe pattern when the wafer is tilted; Figure 6 (b) is the local fringe pattern corresponding to the lower side part of the right region. Figure 6 (c) is the enlarged view of the fringe in figure (b), Figure 6 (d) is Figure 6 the continuous phase pattern corresponding to (c), the phase points of the continuous phase pattern include A, B and C, the phase difference between A and B and the phase difference between A and C are extracted respectively and substituted into the phase formula to calculate the fringe rotation angle and the actual fringe frequency of the first observation area. In the embodiment, the first observation area is the lower side part of the right region (I2), and in other embodiments, the first observation area can also be any side part of other regions (I1, I3, I4).

[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 and cross sections relative to the mask in space x and ε y When the reflected light beam B1 is deflected by 2ε in the two sections respectively x and 2ε y Forming B1', the interference angle becomes θ1+2ε x and θ2+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] Where I2 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 the first angle offset ε when the wafer is tilted relative to the mask in the longitudinal section 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, the second angle offset ε when the wafer is tilted relative to the mask in space is determined 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 relative to the longitudinal section of 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] Further, in the embodiment, the first frequency formula is:

[0074] f l = f0+ 2ε x1 cosθ1 / λ

[0075] wherein f0 is an ideal fringe frequency, f l is an actual fringe frequency, and λ is a wavelength of the incident light.

[0076] The first conversion formula is:

[0077]

[0078] wherein θ1 is a first diffraction angle, θ2 is a second diffraction angle, θ l is a fringe rotation angle, and ε y is a second angular offset of the wafer relative to the mask in the space.

[0079] In step S5, the wafer and the mask are leveled according to the first angular offset ε x and the second angular offset ε y .

[0080] wherein the calculated ε x and ε y may be directly input into a leveling displacement table of a photolithography machine for feedback, and the wafer and the mask are leveled by the leveling displacement table. Alternatively, the ε x and ε y may be verified first, and after verification, the wafer and the mask are leveled by the leveling displacement table of the photolithography machine through feedback.

[0081] Specifically, an upper portion of the right region is determined as the second observation area, and the phases of 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 and the phase difference between the phase points D and F are calculated. and are substituted into the second phase formula to obtain the fringe rotation angle θ u and the actual fringe frequency f u of the second observation area, and the second phase formula is:

[0082]

[0083] The second diffraction angle θ2 and the ideal fringe frequency f0 are substituted into the second frequency formula to obtain the third angular offset ε x ′, and the second frequency formula is:

[0084] f u = f0- 2ε x 'cosθ2 / λ

[0085] The first diffraction angle θ1, the second diffraction angle θ2 and ε x ' are substituted into the second conversion formula to obtain the fourth angle offset ε y ' of the upper side of the right region, and the second conversion formula is:

[0086]

[0087] ε x and ε y are taken as the first group of data, ε x ' and ε y ' are taken as the second group of data, and the two groups of data are compared to verify the accuracy of the measurement. If there is no error or the error is small (which can be determined by setting a threshold), it means that the measurement data is accurate, and if the error is large, it means that the measurement data is inaccurate, and the two groups of data are discarded and re-measured.

[0088] Further, if the error of the two groups of data is less than the threshold, ε x and ε y are input into the leveling displacement table of the lithography machine for feedback, and the wafer and the mask are leveled by the leveling displacement table.

[0089] It should be noted that the present embodiment is based on the right region of the square Moiré fringe pattern to calculate the error of the mask and the wafer in two directions. Correspondingly, the same calculation method can be used to obtain the error of the mask and the wafer in two directions based on other regions. For example, the first angle offset ε x and the second angle offset ε y are calculated based on the left part of the upper region, and the third angle offset ε x ' and the fourth angle offset ε y ' are calculated based on the right part of the upper region, and finally the verified first angle offset ε x and the second angle offset ε y are input into the leveling displacement table of the lithography machine for feedback, and the wafer and the mask are leveled by the leveling displacement table.

[0090] To sum up, the leveling method of the mask and the wafer is provided in the embodiment, the leveling grating located on the surface of the mask is vertically irradiated by the light source, two groups of intersecting diffraction beams are generated by the incident light of the light source through each quadrant of the leveling grating, the two groups of beams respectively generate interference effects with the grating period structure in the horizontal and vertical directions, finally a square interference field is formed, and a square moire fringe pattern is generated, and due to the special structure of the square moire fringe pattern, the interference effects of the four regions in the pattern are interwoven with each other, the interference fringes exhibited can not only respond to the transverse tilt of the wafer, but also respond to the longitudinal tilt of the wafer, therefore, only the phase change of any region in the square moire fringe pattern needs to be measured, then the angle offset amount of the wafer in space relative to the mask when the cross-section tilt and the longitudinal section tilt occur is accurately calculated through formula conversion, the problem that the existing leveling method of the mask and the wafer cannot realize high-precision detection of the tilt angle of multiple interfaces through single-point measurement is solved, and the measurement efficiency and the measurement precision are improved.

[0091] It should be understood that the specific embodiments described herein are merely exemplary and not intended to limit the application. According to the embodiments provided in the present application, all other embodiments obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the present application.

[0092] Obviously, the drawings are only some examples or embodiments of the present application, and those skilled in the art can also apply the present application to other similar situations according to the drawings without creative labor. In addition, it can be understood that although the work done in the development process may be complex and long, certain design, manufacture or production changes made by those skilled in the art according to the technical content disclosed in the present application are only routine technical means and should not be regarded as insufficient disclosure of the present 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, where the leveling grating is located on a mask surface and is divided into four quadrants according to the quadrants. Each quadrant includes a plurality of L-shaped light-shielding lines at equal intervals, and the two sides of each L-shaped light-shielding line are equal in length and perpendicular to the boundaries of the two quadrants. The spacing between the L-shaped light-shielding lines in the first and third quadrants is a first spacing, and the spacing between the L-shaped light-shielding lines in the second and fourth quadrants is a second spacing, the first spacing is greater than the second spacing, and a duty ratio of the plurality of L-shaped light-shielding lines in each quadrant is 1 / 2. Incident light from the light source passes through the first and third quadrants of the leveling grating and is reflected by a wafer to generate a first diffracted beam, and passes through the second and fourth quadrants of the leveling grating and is reflected by the wafer to generate a second diffracted beam. The first diffracted beam and the second diffracted beam interfere with each other to 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 median. Determine a first observation area in the lower portion of the right area, and determine a fringe rotation angle and an actual fringe frequency in the first observation area; The first angle offset ε when the wafer is tilted relative to the mask in the longitudinal section 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, the second angle offset ε when the wafer is tilted relative to the mask in space is determined y , the first conversion formula is: Among them, θ1 is the first diffraction angle, θ2 is the second diffraction angle, θ l is the stripe 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 beam is the first diffraction angle, the angle between the incident light of the light source and the second diffracted 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, wherein: The first spacing is 1.1 times the second spacing.

3. The method for leveling a mask and a wafer according to claim 1, wherein: 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, wherein: Determining the fringe rotation angle and 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, wherein: according to and Determining the fringe rotation angle and 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. The phase formula is: Among them, 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.

6. The method for leveling a mask and a wafer according to claim 1, wherein: 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 relative to the mask in the longitudinal section in space according to the first frequency formula x , the first frequency formula is: f l =f0+2ε x cosθ1 / λ Where f0 is the ideal fringe frequency, f l 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, wherein: 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, wherein: 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, wherein: The method for collecting the generated square moiré fringe pattern is to collect it in real time using a CCD camera.

10. The method for leveling a mask and a wafer according to claim 1, wherein: According to ε x and ε y Leveling the wafer and mask involves 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.

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