Preparation method of grating
By controlling the exposure of photoresist and interference exposure through thickness and duty cycle grayscale masks, the problems of low efficiency and high cost in grating fabrication in existing technologies have been solved, and efficient and low-cost fabrication of diversified grating structures has been achieved.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- APPOTRONICS CORP LTD
- Filing Date
- 2024-10-25
- Publication Date
- 2026-04-28
AI Technical Summary
Existing technologies for fabricating high-performance diffraction gratings suffer from low processing efficiency and high costs due to repeated eclipsing during the etching process. Furthermore, these technologies struggle to meet the precision requirements of tightly connected gradient regions, increasing the probability of defects.
By using grayscale masks with varying thickness and duty cycle to control photoresist exposure, and combining this with interference exposure technology, grating structures with different heights and duty cycles can be formed through two exposures, reducing the number of exposures, improving yield, and lowering costs.
By creating grating structures with different heights and duty cycles through two exposures, production efficiency and yield are significantly improved, manufacturing costs are reduced, and diverse grating design requirements are met.
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Figure CN121934199A_ABST
Abstract
Description
Technical Field
[0001] This application relates to the field of optical technology, specifically to a method for fabricating a grating. Background Technology
[0002] A grating is a diffractive optical element with a periodic spatial structure or optical properties. Its most prominent characteristic is dispersion, which separates incident polychromatic light according to its wavelength along the direction of spatial propagation to form a spectrum. In addition, gratings also possess properties such as phase matching, beam splitting, and polarization. With the development of technology, the application of gratings is no longer limited to spectral analysis; they have also found wide application in information processing fields such as optical waveguides, optical communication, metrology, and astronomy.
[0003] Currently, high-performance diffraction gratings generally require grating structures with different height partitions. The main method for creating these partitions is etching, which involves sequentially masking the different height partitions during the etching process using step-by-step physical masking. However, this method has several drawbacks. First, it increases processing steps, leading to reduced efficiency and higher costs. Second, for tightly connected gradient regions, the stitching accuracy of step-by-step physical masking may not meet design requirements, and multiple masking etching steps increase the probability of introducing defects. Summary of the Invention
[0004] This application provides a method for fabricating a grating to at least partially improve the above-mentioned technical problems.
[0005] The embodiments of this application are implemented through the following technical solutions.
[0006] This application provides a method for fabricating a grating. The grating has multiple partitions, at least two of which have different heights. The method includes: providing a substrate; forming a photoresist layer on the surface of the substrate; providing a thickness grayscale mask, the grayscale distribution of which corresponds one-to-one with the height distribution of the multiple partitions; exposing the photoresist layer to a light beam that can pass through the thickness grayscale mask; performing a first development on the exposed photoresist layer; exposing the photoresist layer after the first development to two coherent light beams for interference exposure; and performing a second development on the photoresist layer after the interference exposure to form the grating.
[0007] In some implementations, the period of the interference fringes formed by the two coherent beams is Where λ is the wavelength of the coherent light, and θ is the angle between the two coherent beams.
[0008] In some embodiments, the thickness grayscale mask is prepared by: establishing a mapping relationship between grayscale values and the amount of photoresist thinning per unit time by a beam; determining the grayscale distribution of the thickness grayscale mask based on the mapping relationship and the height distribution of multiple partitions; and preparing the thickness grayscale mask based on the grayscale distribution of the thickness grayscale mask.
[0009] In some implementations, establishing a mapping relationship between grayscale and the amount of photoresist thinning per unit time under ultraviolet light includes: dividing grayscale values into n levels to form a layout containing a grayscale level, where a≤n; exposing the photoresist to a light beam environment that transmits through the layout to obtain the photoresist thinning amount corresponding to the layout; and establishing a mapping relationship between grayscale and the amount of photoresist thinning per unit dose of ultraviolet light based on the photoresist thinning amount.
[0010] In some implementations, the grayscale distribution of the grayscale mask is such that the grayscale values gradually increase or decrease along a predetermined direction.
[0011] In some implementations, the grayscale mask includes multiple partitions, each partition having the same grayscale value, while adjacent partitions have different grayscale values.
[0012] In some implementations, the areas of two adjacent partitions may be equal or unequal.
[0013] In some embodiments, the photoresist layer after the first development is exposed to two coherent beams for interference exposure, including: providing a duty cycle grayscale mask, the grayscale distribution of which corresponds one-to-one with the duty cycle distribution of multiple partitions; and exposing the photoresist layer after the first development to two coherent beams of light that can pass through the duty cycle grayscale mask for interference exposure.
[0014] In some embodiments, the duty cycle grayscale mask is prepared by: establishing a mapping relationship between grayscale values and the amount of photoresist thinning per unit time by the light beam; determining the grayscale distribution of the duty cycle grayscale mask based on the mapping relationship and the height distribution of multiple partitions; and preparing the duty cycle grayscale mask based on the grayscale distribution of the duty cycle grayscale mask.
[0015] In some embodiments, the multiple partitions of the duty cycle grayscale mask include at least a first partition and a second partition, wherein the grayscale of the first partition is less than the grayscale of the second partition, and the duty cycle of the duty cycle grayscale mask in the region corresponding to the first partition is greater than or less than the duty cycle in the region corresponding to the second partition.
[0016] The grating fabrication method provided in this application involves providing a thickness grayscale mask with a grayscale distribution that corresponds one-to-one with the height distribution of the multiple partitions. During exposure, the light beam is controlled to regulate the thinning of the photoresist layer. After development, a photoresist layer thickness distribution matching the height distribution of the grating is obtained. Then, the grating structure is directly formed on the photoresist layer using interference exposure. Grating structures with different height partitions can be formed through two exposures. Compared to existing technologies, this reduces the number of exposures, significantly improves yield, lowers manufacturing costs, and allows for the fabrication of grating structures with various height designs. Attached Figure Description
[0017] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.
[0018] Figure 1 This is a schematic diagram of a grating structure shown in an embodiment of this application.
[0019] Figure 2 This is a flowchart of a grating fabrication method proposed in an embodiment of this application.
[0020] Figure 3 This is a schematic diagram of the process state of a grating fabrication method proposed in an embodiment of this application.
[0021] Figure 4 This is a flowchart of step S120 in a grating fabrication method proposed in an embodiment of this application.
[0022] Figure 5 This is a schematic diagram of a layout structure shown in a method for fabricating a grating according to an embodiment of this application.
[0023] Figure 6 This is a graph showing the relationship between the grayscale value obtained in a grating fabrication method proposed in this application and the remaining photoresist thickness after photoresist etching by the light beam per unit time.
[0024] Figure 7 This is a schematic diagram of another grating structure shown in an embodiment of this application.
[0025] Figure 8 This is a flowchart of another method for fabricating a grating proposed in an embodiment of this application.
[0026] Figure 9 This is a schematic diagram of the process state of another grating fabrication method proposed in the embodiments of this application.
[0027] Figure 10 This is a flowchart of step S240 in another grating fabrication method proposed in the embodiments of this application. Detailed Implementation
[0028] To enable those skilled in the art to better understand the present invention, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of them. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are within the scope of protection of the present invention.
[0029] Figure 1 A grating structure 10 is shown, which has multiple partitions, which can be two or more. At least two of the partitions contain partitions of different heights, and each partition can have the same or different area or width; this embodiment does not limit this. This is merely an example. Figure 1 The raster structure 10 shown contains three partitions, namely the first partition 11, the second partition 12, and the third partition 13. The heights of the first partition 11, the second partition 12, and the third partition 13 are all different, and the widths of the first partition 11, the second partition 12, and the third partition 13 are also different.
[0030] In the existing technology, if you want to prepare Figure 1 The grating structure 10 shown requires that during exposure, the second partition 12 and the third partition 13 are first blocked, and the first partition 11 is exposed separately. Then, the first partition 11 and the third partition 13 are blocked, and the second partition 12 is exposed separately. Finally, the first partition 11 and the second partition 12 are blocked, and the third partition 13 is exposed separately. When the number of partitions exceeds three, the number of exposures will increase further. This preparation method has a serious problem with product yield due to the large number of exposures, and multiple exposures will lead to a significant increase in manufacturing costs.
[0031] Please refer to the following: Figure 2 and Figure 3 This embodiment provides a method for fabricating a grating, including steps S110-S150.
[0032] Step S110: Provide a substrate and form a photoresist layer on the surface of the substrate.
[0033] Depending on the application requirements, the substrate 20 can be selected from silicon (Si), sapphire, silicon carbide (SiC), gallium nitride (GaN), aluminum nitride (AlN), etc., and this embodiment does not limit it.
[0034] The substrate 20 is typically a planar substrate with two opposing surfaces, such as Figure 3 As shown in (A), the photoresist layer 30 can be formed on one of the surfaces of the substrate 20. The photoresist layer 30 can be uniformly formed on the surface of the substrate 20, for example, the photoresist layer 30 has the same thickness at all points on the substrate 20. Of course, in some embodiments, the photoresist layer 30 may also have uneven thickness. In addition, the thickness of the photoresist layer 30 should be at least greater than the maximum thickness of the grating structure to be fabricated. The method of forming the photoresist layer 30 on the surface of the substrate 20 can be spin coating or the like, and this embodiment is not limited to this.
[0035] Step S120: Provide a thick grayscale mask and expose the photoresist layer to a light beam that can pass through the thick grayscale mask for exposure.
[0036] The thickness grayscale mask 40 is a device used for controlling the light dose of exposure. The grayscale distribution of the thickness grayscale mask 40 corresponds one-to-one with the height distribution of multiple zones. The thickness grayscale mask 40 can be pre-designed, and the grayscale values correspond one-to-one with the thickness distribution of the grating to be fabricated. Figure 1 Taking the grating shown as an example, the grating includes a first partition, a second partition, and a third partition. The thickness grayscale mask 40 corresponding to the grating may also include three partitions. The three partitions correspond one-to-one with the first partition, the second partition, and the third partition. The grayscale values of the three partitions are not equal, so that the transmittance of the light beam is not equal when passing through the three partitions.
[0037] like Figure 3 As shown in (B), when the light beam passes through the thick grayscale mask 40, the transmittance of the light beam is different depending on the grayscale value at the current position. As a result, the amount of etching of the photoresist layer 30 after the light beam passes through the thick grayscale mask 40 is not equal, resulting in different thickness distributions of the photoresist layer 30.
[0038] The light beam can be a laser beam, which has advantages such as high collimation, strong monochromaticity, high precision, and easy control. It also avoids wetting the surface of the photoresist layer 30 during exposure. More specifically, the light beam can be an ultraviolet light beam. Ultraviolet light has a short wavelength, allowing for accurate focusing and the creation of very fine structures. Simultaneously, it has high photon energy, resulting in high etching efficiency. Furthermore, ultraviolet light exhibits less thermal deposition and light attenuation during processing, leading to less damage to the material. Of course, in other embodiments, the light beam can be other types, such as blue light, and this embodiment does not limit this.
[0039] In one implementation, see [reference] Figure 4 The preparation method of the thickness grayscale mask 4 may include steps S121-S123:
[0040] Step S121: Establish the mapping relationship between grayscale value and the amount of photoresist thinning per unit dose of light beam.
[0041] The mapping relationship between grayscale values and the amount of photoresist thinning per unit time refers to the amount of photoresist thinning per unit time corresponding to different grayscale values. The corresponding photoresist beam is the same as the beam used during exposure. In some implementations, grayscale values can be digitally divided to more accurately establish the mapping relationship between grayscale values and the amount of photoresist thinning per unit time. For example, grayscale values can be divided into n levels, each level corresponding to a different grayscale value. A grayscale value of 0 represents a transmittance of 0, and a grayscale value of n represents a transmittance of 100%. To improve etching accuracy, n can be set larger; in one implementation, n can be 255, resulting in 256 grayscale levels from 0 to 255.
[0042] When obtaining the mapping relationship between grayscale values and the amount of photoresist thinning per unit time by the light beam, a grayscale pattern of order a can be formed (e.g., ...). Figure 5 As shown in the figure, where a≤n, it can be understood that the number of layouts can be one or more. In one embodiment, a can be, for example, 16. The photoresist is exposed under a light beam that passes through the layout. After exposure, the remaining photoresist thickness is measured using a profilometer. Based on the initial thickness of the photoresist layer 30, the photoresist thinning amount corresponding to the layout can be obtained. During measurement, multiple layouts can be measured sequentially to obtain a sufficient sample size, so that the subsequent mapping relationship is more accurate. To further improve the measurement accuracy, multiple measurements can be performed on the same layout, and the average value of the photoresist thinning amount is taken as the measurement value.
[0043] Based on the mapping relationship between the obtained grayscale value and the amount of photoresist thinning per unit time of the light beam, a corresponding curve was plotted. Figure 6 A graph showing the relationship between grayscale value and the remaining photoresist thickness after photoresist etching by a light beam per unit time is presented. The horizontal axis represents the grayscale value, and the vertical axis represents the residual photoresist thickness. The graph shows that a smaller grayscale value indicates lower light transmittance, less photoresist etching, and a larger residual photoresist thickness. Conversely, an increase in grayscale value results in a smaller residual photoresist thickness. Based on the grayscale value, the remaining amount of photoresist can be obtained, and the photoresist thinning amount can be calculated. The corresponding grayscale value can then be determined based on the remaining or thinned amount of photoresist.
[0044] Step S122: Determine the grayscale distribution of the thickness grayscale mask based on the mapping relationship and the height distribution of multiple partitions.
[0045] Based on the height distribution of different partitions and the thickness of the initial photoresist layer 30, the amount of photoresist thinning or remaining amount in different partitions can be determined. Based on the mapping relationship obtained in step S121, the gray level of each partition in the thickness gray level mask 40 can be determined, thereby obtaining the gray level distribution.
[0046] Step S123: Prepare a thickness grayscale mask based on the grayscale distribution of the thickness grayscale mask.
[0047] The thickness grayscale mask 40 obtained by the above method has a grayscale distribution that corresponds one-to-one with the height distribution of multiple partitions. Only one exposure is needed to form a thickness distribution that matches the grating structure, which significantly improves production efficiency and yield and saves manufacturing costs.
[0048] The grayscale mask 40 prepared in the above manner, depending on the design parameters of the grating to be prepared, can, in one possible implementation, exhibit a gradual grayscale distribution along a predetermined direction. This gradual distribution can involve a gradual increase or decrease in grayscale values. The predetermined direction can be any direction on a plane, or a radial direction outward from the center, etc. In another possible implementation, the grayscale distribution can include multiple partitions, each with the same grayscale value. Adjacent partitions may have different grayscale values; however, non-adjacent partitions may have the same or different grayscale values. Furthermore, the area of each partition can be equal or unequal, and the width of each partition can also be equal or unequal.
[0049] Step S130: Perform the first development on the exposed photoresist layer.
[0050] During exposure, the exposed photoresist layer 30 undergoes a chemical change that makes it dissolvable. The exposed photoresist layer 30 is then placed in a developing solution for development. Figure 3 As shown in (C), the developer can dissolve the exposed photoresist layer 30, forming a photoresist layer 30 with a thickness distribution matching the grating. The developer can be, for example, a positive developer, such as an aqueous solution of tetramethylammonium hydroxide (TMAH), sodium hydroxide, or potassium hydroxide; or a negative developer, such as an organic solvent like xylene. After the first development, a photoresist layer 30 with a thickness distribution matching the grating is obtained.
[0051] Step S140: Expose the photoresist layer after the first development to two coherent beams for interference exposure.
[0052] like Figure 3 As shown in (D), interference exposure is a technique that utilizes the interference phenomenon of light to fabricate optical components or patterns. Its basic principle is to split a laser source into two or more beams, then synthesize them on a sample coated with photoresist, forming interference on the photoresist layer 30. For example... Figure 3As shown in (E), due to the interference phenomenon of light, regular interference fringes are generated on the sample. These fringes cause the sample to produce a regular wavy pattern after exposure. The grating has a concave-convex structure, so the grating structure can be directly formed on the photoresist layer 30 that has been matched with the thickness distribution of the grating through interference exposure.
[0053] The two coherent beams can be composed of two beams from different light sources, or they can be formed by separating beams from the same light source. This embodiment does not limit this. The coherent beams can also be ultraviolet light, and further, they can also be laser light.
[0054] During the interference exposure process, the parameters of the two coherent beams can be adjusted accordingly based on the grating parameters required for the fabricated grating. For example, the incident positions of the two coherent beams can be adjusted according to the duty cycle of the grating, thereby changing the period of the interference fringes formed by the two beams. This allows for the formation of grating structures with different widths. The period of the interference fringes formed by the two coherent beams is... Where λ is the wavelength of the coherent light, and θ is the angle between the two coherent beams. The larger θ is, the larger the period of the interference fringes formed by the two coherent beams; the smaller θ is, the smaller the period of the interference fringes formed by the two coherent beams.
[0055] Step S150: The photoresist layer after interference exposure is developed a second time to form a grating.
[0056] like Figure 3 As shown in (F), after interference exposure, the photoresist layer 30 undergoes a second development to obtain the grating, which has partitions of varying thicknesses. The second development process can be performed in the same manner as the first development process, and will not be described in detail here.
[0057] The grating fabrication method provided in this embodiment involves providing a thickness grayscale mask 40 with a grayscale distribution that corresponds one-to-one with the height distribution of multiple zones. During exposure, the light beam is controlled to regulate the thinning amount of the photoresist layer 30. After development, a photoresist layer 30 thickness distribution matching the height distribution of the grating is obtained. Then, the grating structure is directly formed on the photoresist layer 30 using interference exposure. By using only two exposures, grating structures with different height zones can be formed. Compared to existing technologies, this method reduces the number of exposures, significantly improves yield, lowers manufacturing costs, and allows for the fabrication of grating structures with various height designs.
[0058] In other embodiments, the grating structure 10 not only has varying height partitions, but the gratings within different partitions may also have varying duty cycles. Figure 7 A grating structure 10 is shown. Figure 7The raster structure 10 shown contains three partitions: a first partition 11, a second partition 12, and a third partition 13. The heights and widths of the three partitions are all different. Furthermore, the duty cycles of the raster structure 10 in the first partition 11, the second partition 12, and the third partition 13 are also different.
[0059] by Figure 7 Taking the grating structure 10 shown as an example, the grating includes a first partition 11, a second partition 12, and a third partition 13. The corresponding thickness grayscale mask can also include three partitions. The three partitions correspond one-to-one with the first partition 11, the second partition 12, and the third partition 13. The grayscale values of the three partitions are not equal, so that the transmittance of the light beam is not equal when passing through the three partitions. At the same time, the duty cycles of the first partition 11, the second partition 12, and the third partition 13 are all different.
[0060] At this point, this embodiment provides another method for fabricating the grating, please refer to it as well. Figure 8 and Figure 9 The method for fabricating the grating may include the following steps S210-S250. It should be noted that the same steps can be found in the content of the foregoing embodiments and will not be repeated here.
[0061] Step S210: Provide a substrate and form a photoresist layer on the surface of the substrate.
[0062] Step S220: Provide a thick grayscale mask and expose the photoresist layer to a light beam that can pass through the thick grayscale mask for exposure.
[0063] Step S230: Perform the first development on the exposed photoresist layer.
[0064] Step S240: Provide a duty cycle grayscale mask, the grayscale distribution of which corresponds one-to-one with the duty cycle distribution of multiple partitions.
[0065] The duty cycle of a grating refers to the ratio between the transparent and opaque areas in the grating, usually represented by f. The calculation formula is f = w / P, where w is the width of the transparent area (or ridge) and P is the grating period, which is the distance between two adjacent transparent areas (or ridges).
[0066] To prepare gratings with different duty cycles in different partitions, the interference fringes irradiated by the photoresist layer 30 need to have different fringe periods in different partitions. However, the period of the interference fringes formed by the two coherent beams is fixed, so it is necessary to further modulate the interference fringes formed by the two coherent beams.
[0067] like Figure 9 As shown in (D), the duty cycle grayscale mask 50 is a device used for photodigestion control of the exposure light amount. The grayscale distribution of the duty cycle grayscale mask 50 corresponds one-to-one with the duty cycle distribution of multiple zones. The duty cycle grayscale mask 50 can be pre-designed, and the grayscale values correspond one-to-one with the duty cycle distribution of the grating to be prepared. The grayscale value distributions of the three zones are different, causing the interference fringes formed by the two coherent beams to have different duty cycle distributions when passing through the three zones.
[0068] When interference fringes pass through the duty cycle grayscale mask 50, the transmittance of the light beam is different depending on the grayscale value at the current position. As a result, the etched area of the photoresist layer 30 after the light beam passes through the duty cycle grayscale mask 50 is different, resulting in different duty cycle distributions of the photoresist layer 30.
[0069] In one implementation, see [reference] Figure 10 The preparation method of the thickness grayscale mask 40 may include steps S241-S243:
[0070] Step S241: Establish the mapping relationship between grayscale value and the amount of photoresist thinning per unit dose of light beam.
[0071] Step S242: Determine the grayscale distribution of the duty cycle grayscale mask based on the mapping relationship and the duty cycle distribution of multiple partitions.
[0072] Based on the duty cycle distribution of different partitions and the initial thickness of the photoresist layer 30, the amount of photoresist thinning or remaining amount in different partitions can be determined. Based on the mapping relationship obtained in step S241, the grayscale distribution of each partition in the duty cycle grayscale mask 50 can be determined, and thus the grayscale distribution can be obtained.
[0073] Step S243: Prepare a duty cycle grayscale mask based on the grayscale distribution of the duty cycle grayscale mask.
[0074] The duty cycle grayscale mask 50 obtained by the above method has a grayscale distribution that corresponds one-to-one with the duty cycle distribution of multiple partitions. Only one exposure is needed to form a duty cycle distribution that matches the grating structure, which significantly improves production efficiency and yield and saves manufacturing costs.
[0075] The above-described fabrication method can produce grayscale masks 50 with different duty cycles according to various duty cycle requirements. For example, the fabricated grayscale mask 50 may have multiple partitions, including at least a first partition and a second partition. The grayscale value of the first partition is less than that of the second partition. The duty cycle of the grayscale mask 50 in the region corresponding to the first partition is greater than that in the region corresponding to the second partition. In this case, the grating has a larger duty cycle where the thickness is smaller and a smaller duty cycle where the thickness is larger. In other embodiments, the grayscale value of the first partition is less than that of the second partition. The duty cycle of the grayscale mask 50 in the region corresponding to the first partition is less than that in the region corresponding to the second partition. In this case, the grating has a larger duty cycle where the thickness is larger and a smaller duty cycle where the thickness is smaller.
[0076] Step S250: Expose the photoresist layer after the first development to two coherent beams of light that can pass through the duty cycle grayscale mask for interference exposure.
[0077] like Figure 9 As shown in Figure (E), after the interference fringes formed by the two coherent beams pass through the duty cycle grayscale mask 50, the duty cycle of the interference fringes changes in different partitions, which in turn changes the etching position of the photoresist layer 30. The amount and position of the photoresist that undergoes chemical reaction after exposure are matched with the grating.
[0078] Step S260: Perform a second development on the photoresist layer after interference exposure to form a grating.
[0079] After interference exposure, the photoresist layer 30 is developed a second time to obtain the grating, which has partitions of different thicknesses and different duty cycles in different partitions.
[0080] The grating fabrication method provided in this embodiment involves providing a thickness grayscale mask with a one-to-one grayscale distribution corresponding to the height distribution of the multiple partitions. During exposure, the light beam is controlled to regulate the thinning of the photoresist layer. After development, a photoresist layer thickness distribution matching the height distribution of the grating is obtained. Then, by providing a duty cycle grayscale mask, interference exposure is used to directly form grating structures with different duty cycle differences on the photoresist layer. Grating structures with different height partitions and different duty cycle partitions can be formed through two exposures. Compared to existing technologies, this method reduces the number of exposures, significantly improves yield, lowers manufacturing costs, and allows for the fabrication of grating structures with various height designs.
[0081] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included within the protection scope of the present invention.
Claims
1. A method for fabricating a grating, characterized in that, The grating has multiple partitions, and the multiple partitions include at least two partitions with different heights. The method includes: A substrate is provided, and a photoresist layer is formed on the surface of the substrate; A thick grayscale mask is provided, wherein the grayscale distribution of the thick grayscale mask corresponds one-to-one with the height distribution of the plurality of partitions, and the photoresist layer is exposed to a light beam that can pass through the thick grayscale mask for exposure. The exposed photoresist layer is then developed for the first time. The photoresist layer after the first development is exposed to two beams of coherent light for interference exposure; The photoresist layer after interference exposure is developed a second time to form the grating.
2. The method according to claim 1, characterized in that, The period of the interference fringes formed by the two coherent beams is Where λ is the wavelength of the coherent light, and θ is the angle between the two coherent beams.
3. The method according to claim 1 or 2, characterized in that, The thickness grayscale mask is prepared in the following manner: Establish the mapping relationship between grayscale values and the amount of photoresist thinning per unit time by the light beam; The grayscale distribution of the thickness grayscale mask is determined based on the mapping relationship and the height distribution of the multiple partitions. The thickness grayscale mask is prepared based on the grayscale distribution of the thickness grayscale mask.
4. The method according to claim 3, characterized in that, The establishment of the mapping relationship between grayscale and the amount of photoresist thinning per unit time by ultraviolet light includes: The grayscale values are divided into n levels to form a layout containing a grayscale level, where a≤n; The photoresist is exposed to a light beam that passes through the pattern to obtain the photoresist thinning amount corresponding to the pattern. Based on the amount of photoresist thinning, a mapping relationship is established between grayscale and the amount of photoresist thinning per unit dose of ultraviolet light.
5. The method according to claim 1 or 2, characterized in that, The grayscale distribution of the grayscale mask is such that the grayscale value gradually increases or gradually decreases along a predetermined direction.
6. The method according to claim 1 or 2, characterized in that, The grayscale mask comprises multiple partitions, each partition having the same grayscale value, while adjacent partitions have different grayscale values.
7. The method according to claim 6, characterized in that, The areas of two adjacent partitions may be equal or unequal.
8. The method according to claim 1, characterized in that, The process of exposing the photoresist layer after the first development to two beams of coherent light for interference exposure includes: A duty cycle grayscale mask is provided, wherein the grayscale distribution of the duty cycle grayscale mask corresponds one-to-one with the duty cycle distribution of the multiple partitions; The photoresist layer after the first development is exposed to two coherent beams of light that can pass through a duty cycle grayscale mask for interference exposure.
9. The method according to claim 8, characterized in that, The duty cycle grayscale mask is prepared in the following manner: Establish the mapping relationship between grayscale values and the amount of photoresist thinning per unit time by the light beam; The grayscale distribution of the duty cycle grayscale mask is determined based on the mapping relationship and the height distribution of the multiple partitions. The duty cycle grayscale mask is prepared based on the grayscale distribution of the duty cycle grayscale mask.
10. The method according to claim 8 or 9, characterized in that, The duty cycle grayscale mask comprises at least a first partition and a second partition, wherein the grayscale of the first partition is less than that of the second partition, and the duty cycle of the duty cycle grayscale mask in the region corresponding to the first partition is greater than or less than the duty cycle in the region corresponding to the second partition.