Preparation method of exposure pattern and metasurface structure

Abstract

The invention provides a preparation method of an exposure pattern and a metasurface structure. The preparation method comprises the following steps: S10, coating a substrate slice with a bottom layer photoresist and curing the bottom layer photoresist; s20, coating the cured bottom layer photoresist with a top layer photoresist and curing the top layer photoresist; s30, exposing the substrate sheet coated with the bottom photoresist and the top photoresist through an interference exposure process; s40, developing the exposed substrate slice, and transferring a preset pattern to the photoresist on the surface of the substrate; wherein the top layer photoresist and the bottom layer photoresist have different exposure sensitivities. According to the invention, a double-layer glue structure is adopted for interference exposure, so that the photoresist in a place with small exposure field intensity is sensitive to light as little as possible or not sensitive to light, and the photoresist in a place with large exposure field intensity is sensitive to light as much as possible or completely sensitive to light, thereby achieving the effect of enhancing contrast; the defects that in the super-surface structure preparation process, the light field intensity interfering exposure changes in a sine curve mode, so that the contrast ratio of a photoresist pattern is low, and the side wall is inclined are overcome, and the photoetching process quality is improved.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor processes in microelectronic processes, and particularly relates to a method for preparing an exposure pattern and a metasurface structure. Background Art

[0002] With the development of optoelectronic technologies, microscale metasurface structures (hereinafter referred to as metasurface structures) are increasingly applied to semiconductor optoelectronic devices. A metasurface structure is a large-area micro-nano structure composed of sub-wavelength small-sized structures, and has the characteristics of miniaturization and high integration. Compared with traditional refractive or diffractive optical systems, metasurface structures exhibit excellent properties in light field regulation and can achieve complex functions. For example, the polarization, spectrum, and phase of the light field can be regulated to detect higher-dimensional information of the light field; or the reflection or refraction properties of the light field can be changed to greatly improve the performance of optoelectronic devices. Combining metasurface structures with traditional optoelectronic detectors (such as infrared detectors) to expand the functions and application ranges of optoelectronic detectors has gradually become one of the development directions of next-generation optoelectronic detectors.

[0003] The metasurface structure capable of realizing the light field regulation function needs to reach the sub-wavelength scale line width. The exposure equipment capable of preparing such low-line-width patterns is expensive, and generally takes a long time to complete the exposure process of the metasurface structure. These factors make the preparation of metasurface structures difficult and limit the use range of metasurface structures. The interference exposure technology can obtain an exposure pattern with a lower line width without using a complex projection optical system, and does not require the preparation of an expensive low-line-width structure mask plate, and the exposure speed is also relatively fast, so that a lower manufacturing cost can be achieved.

[0004] However, the principle of the interference exposure technology determines that the light intensity of the interference exposure changes according to a sine curve. As Figure 1 and Figure 2 shown, there is a large transition region (incomplete exposure region) between the exposure region and the non-exposure region, resulting in the side wall of the finally formed photoresist pattern being inclined, with poor morphology compared with the traditional lithography process, affecting the subsequent etching or stripping process and reducing the process effect. Summary of the Invention

[0005] The technical problem to be solved by the present invention is how to improve the preparation effect of the exposure pattern of the metasurface structure at low cost. The present invention proposes a method for preparing an exposure pattern and a metasurface structure.

[0006] According to an embodiment of the present invention, a method for preparing an exposure pattern of a metasurface structure includes: S10, coating a bottom photoresist on a substrate wafer and curing it; S20, coating a top photoresist on the cured bottom photoresist and curing it; S30, expose the substrate wafer coated with the bottom photoresist and the top photoresist through an interference exposure process; S40, develop the exposed substrate wafer to transfer the preset pattern to the photoresist on the substrate surface; Wherein, the top photoresist and the bottom photoresist have different exposure sensitivities.

[0007] According to the method for preparing an exposure pattern of a metasurface structure according to an embodiment of the present invention, by using a double-layer photoresist with different exposure sensitivities for interference exposure, the problems of low contrast of the photoresist pattern and inclined sidewalls caused by the sinusoidal change of the light field intensity in the interference exposure during the preparation process of the metasurface structure can be effectively improved, and the quality of the lithography process can be enhanced.

[0008] According to some embodiments of the present invention, the bottom photoresist and the top photoresist are both positive photoresists or both negative photoresists at the same time.

[0009] In some embodiments of the present invention, the thickness ratio of the top photoresist to the bottom photoresist is not greater than 1.

[0010] According to some embodiments of the present invention, the exposure sensitivity of the top photoresist is greater than that of the bottom photoresist.

[0011] In some embodiments of the present invention, the exposure pattern is a grating pattern or a dot matrix pattern formed by interference exposure.

[0012] According to some embodiments of the present invention, the metasurface structure is a micro-scale metasurface structure, and the line width of the exposure pattern is a sub-wavelength scale line width.

[0013] In some embodiments of the present invention, the line width of the exposure pattern does not exceed 1 μm.

[0014] In some embodiments of the present invention, the curing processes in steps S10 and S20 both adopt a baking curing process.

[0015] According to the method for preparing a metasurface structure according to an embodiment of the present invention, the method includes: A10, adopt the method for preparing an exposure pattern of a metasurface structure as described above to form a photoresist with a preset pattern on the metasurface structure; A20, based on the photoresist with a preset pattern, perform an etching and stripping process on the surface of the substrate wafer to prepare a metasurface with a preset structure.

[0016] The preparation method of the metasurface structure according to the embodiment of the present invention uses a double-layer resist structure with a higher sensitivity of the top-layer photoresist than that of the bottom-layer photoresist for interference exposure, which can minimize or avoid the exposure of the photoresist in areas with low exposure field intensity, while maximizing the exposure of the photoresist in areas with high exposure field intensity, achieving the effect of enhancing the contrast and improving the disadvantages of low photoresist pattern contrast and sidewall inclination caused by the sinusoidal variation of the light field intensity in the interference exposure during the preparation process of the metasurface structure, thereby improving the quality of the lithography process.

[0017] According to some embodiments of the present invention, the metasurface structure is applied to an optical detector. Brief Description of the Drawings

[0018] Figure 1 It is a schematic diagram of the light field intensity distribution of interference exposure; Figure 2 It is a schematic diagram of the photoresist morphology of interference exposure; Figure 3 It is a schematic diagram of coating a double-layer photoresist on a substrate wafer according to an embodiment of the present invention; Figure 4 It is a schematic diagram of the interference exposure effect after using a double-layer photoresist according to an embodiment of the present invention; Figure 5 It is a schematic diagram of the morphology of interference exposure with a double-layer photoresist according to an embodiment of the present invention; Figure 6 It is a schematic diagram of the exposure pattern of the metasurface structure prepared by interference exposure according to an embodiment of the present invention. Detailed Embodiments

[0019] To further elaborate on the technical means and effects adopted by the present invention to achieve the predetermined purpose, the present invention will be described in detail as follows in combination with the accompanying drawings and preferred embodiments.

[0020] In the present invention, the description of the method flow in the specification and the steps in the flow chart in the accompanying drawings of the present invention do not necessarily need to be strictly executed according to the step numbers. The execution order of the method steps can be changed. Moreover, certain steps can be omitted, multiple steps can be combined into one step for execution, and / or one step can be decomposed into multiple steps for execution.

[0021] The present invention proposes a metasurface structure interference exposure process, which improves the lithography contrast of the interference exposure process by improving the process, greatly improves the quality of the photoresist morphology after lithography development, and realizes a high-quality preparation process for the metasurface structure.

[0022] The preparation method of the exposure pattern of the metasurface structure according to the embodiment of the present invention includes: S10, coating a bottom-layer photoresist on a substrate wafer and curing it; S20, coat the top photoresist on the cured bottom photoresist and cure it; the substrate wafer after curing the top photoresist is as Figure 3 shown.

[0023] S30, expose the substrate wafer coated with the bottom photoresist and the top photoresist through an interference exposure process; S40, develop the exposed substrate wafer to transfer the preset pattern to the photoresist on the substrate surface. The superstructure surface after completing the preparation of the exposed pattern is as Figure 5 and Figure 6 shown; wherein, the top photoresist and the bottom photoresist have different exposure sensitivities.

[0024] According to the method for preparing an exposed pattern of a metasurface structure according to an embodiment of the present invention, by using a double-layer photoresist with different exposure sensitivities for interference exposure, the problems of low contrast of the photoresist pattern and inclined sidewalls caused by the sinusoidal change of the light field intensity in the interference exposure in the metasurface structure preparation process can be effectively improved, and the quality of the lithography process can be enhanced.

[0025] According to some embodiments of the present invention, the exposure sensitivity of the top layer photoresist is greater than that of the bottom layer photoresist. It should be noted that the greater the exposure sensitivity, the smaller the minimum light energy or the minimum charge amount (for electron beam photoresist) incident per unit area that causes all the photoresist to react. As Figure 5 shown, by using a double-layer resist structure with a higher sensitivity of the top photoresist than that of the bottom photoresist for interference exposure, between the fully exposed area and the non-exposed area, the top photoresist has a large exposure sensitivity and requires less light energy to react, forming a side with a greater inclination; the bottom photoresist has a small exposure sensitivity and requires more light energy to react, forming a side nearly perpendicular to the substrate wafer. Thus, the photoresist in the area with a small exposure field intensity can be made to be less sensitive or not sensitive as much as possible, while the photoresist in the area with a large exposure field intensity can be made to be more sensitive or fully sensitive as much as possible, achieving the effect of enhancing the contrast.

[0026] According to some embodiments of the present invention, both the bottom photoresist and the top photoresist are positive photoresists, or both are negative photoresists. It should be noted that when both the bottom photoresist and the top photoresist are positive photoresists, a positive lithography process can be selected; when both the bottom photoresist and the top photoresist are negative photoresists, a negative lithography process can be selected.

[0027] In some embodiments of the present invention, the thickness ratio of the top photoresist to the bottom photoresist is not greater than 1. That is to say, the thickness of the bottom photoresist is set to be greater than that of the top photoresist. Combining Figure 5As shown, the side of the bottom photoresist is nearly perpendicular to the substrate wafer, and the top photoresist forms a side with a larger inclination. Setting the thickness of the bottom photoresist to be large can make the regions on both sides of the gap of the obtained exposure pattern have a greater height perpendicular to the substrate wafer, thus facilitating subsequent processes such as etching.

[0028] In some embodiments of the present invention, the exposure pattern is a grating pattern or a dot matrix pattern formed by interference exposure. As Figure 6 shown, by using the method for preparing an exposure pattern of the metasurface structure of the present invention, it is possible to prepare a grating pattern as shown in Figure 6 (a), and it is also possible to prepare a dot matrix pattern as shown in Figure 6 (b). It can be understood that the exposure pattern is not limited to the above-mentioned grating pattern and dot matrix pattern, and can also be prepared into other exposure patterns of any shape according to actual needs.

[0029] According to some embodiments of the present invention, the metasurface structure is a microscale metasurface structure, and the line width of the exposure pattern is a sub-wavelength scale line width. In some embodiments of the present invention, the line width of the exposure pattern does not exceed 1 μm. It should be emphasized that when preparing an exposure pattern with a line width in the microscale sub-wavelength scale, the morphology of the photoresist after interference exposure has a great influence on the preparation of the superstructure surface. By using the method for preparing an exposure pattern of the metasurface structure of the present invention, a photoresist with a better morphology can be obtained after interference exposure, thereby effectively improving the preparation quality of the metasurface structure.

[0030] In some embodiments of the present invention, the curing processes in steps S10 and S20 both adopt a baking curing process. The baking curing process is simple, low-cost, and easy to implement.

[0031] According to the method for preparing a metasurface structure of an embodiment of the present invention, the method includes: A10, using the method for preparing an exposure pattern of the metasurface structure as above to prepare a photoresist with a preset pattern on the metasurface structure; A20, based on the photoresist with the preset pattern, performing etching and stripping processes on the surface of the substrate wafer to prepare a superstructure surface with a preset structure.

[0032] According to the method for preparing a metasurface structure of an embodiment of the present invention, by using a double-layer resist structure in which the sensitivity of the top photoresist is higher than that of the bottom photoresist for interference exposure, it is possible to make the photoresist in the place where the exposure field intensity is small less sensitive or not sensitive as much as possible, and at the same time make the photoresist in the place where the exposure field intensity is large more sensitive or fully sensitive as much as possible, achieving the effect of enhancing the contrast, improving the disadvantages of low contrast and inclined sidewalls of the photoresist pattern caused by the sinusoidal curve change of the light field intensity in the interference exposure in the metasurface structure preparation process, and improving the quality of the lithography process.

[0033] According to some embodiments of the present invention, the metasurface structure is applied to an optical detector. It can be understood that the metasurface prepared in the present invention can also be applied to any other optical device that requires a metasurface structure.

[0034] The solution of the present invention will be described in detail below with reference to the accompanying drawings in a specific embodiment. It can be understood that the following description is only an exemplary description and should not be construed as a specific limitation of the present invention. As Figures 3 - 6 shown, first, a low-sensitivity bottom layer of photoresist is coated on the surface of the substrate and baked. After the bottom layer of photoresist is cured, a high-sensitivity top layer of photoresist is coated and baked for curing. Then, interference exposure is used to perform pattern exposure of the metasurface structure on the surface of the substrate. Finally, the exposed photoresist is removed by development, and the metasurface structure pattern is transferred to the photoresist. Among them: The top layer of photoresist and the bottom layer of photoresist must both be positive photoresist or both be negative photoresist; The thickness ratio of the top layer of photoresist to the bottom layer of photoresist should not be greater than 1:1; The exposure sensitivity of the top layer of photoresist should be greater than the exposure sensitivity of the bottom layer of photoresist; The exposed pattern structure includes a grating pattern, a dot matrix pattern formed by interference exposure, and various other pattern structures that can be formed by interference exposure.

[0035] Through the description of the specific implementation manner, it should be possible to have a more in-depth and specific understanding of the technical means and effects adopted by the present invention to achieve the predetermined purpose. However, the accompanying drawings are only for reference and illustration, and are not used to limit the present invention.

Claims

1. A method for preparing an exposure pattern of a super surface structure, characterized in that: include: S10, coating a bottom layer photoresist on the substrate and curing the photoresist; S20, coating a top layer of photoresist on the cured bottom layer of photoresist and curing the top layer of photoresist; S30, exposing the substrate coated with the bottom layer photoresist and the top layer photoresist through an interference exposure process; S40, developing the exposed substrate to transfer the preset pattern to the photoresist on the substrate surface; The top layer photoresist and the bottom layer photoresist have different exposure sensitivities.

2. The method for preparing an exposure pattern of a super surface structure according to claim 1, characterized in that: The exposure sensitivity of the top layer of glue is greater than the exposure sensitivity of the bottom layer of glue.

3. The method for preparing an exposure pattern of a super surface structure according to claim 1, characterized in that: The bottom layer photoresist and the top layer photoresist are both positive photoresists or both negative photoresists.

4. The method for preparing an exposure pattern of a super surface structure according to claim 1, characterized in that: The ratio of the thickness of the top photoresist to the thickness of the bottom photoresist is not greater than 1.

5. The method for preparing an exposure pattern of a super surface structure according to claim 1, characterized in that: The exposure pattern is a grating pattern or a dot pattern formed by interference exposure.

6. The method for preparing an exposure pattern of a super surface structure according to claim 1, characterized in that: The supersurface structure is a microscale supersurface structure, and the line width of the exposure pattern is a sub-wavelength scale line width.

7. The method for preparing an exposure pattern of a super surface structure according to claim 6, characterized in that: The line width of the exposure pattern does not exceed 1 μm.

8. The method for preparing an exposure pattern of a super surface structure according to claim 1, characterized in that: The curing processes in step S10 and step S20 both adopt a baking curing process.

9. A method for preparing a super surface structure, characterized in that: The method comprises: A10, using the method for preparing an exposure pattern of a super surface structure according to any one of claims 1 to 8, preparing a photoresist of a preset pattern on the super surface structure; A20, based on the photoresist with a preset pattern, etching and stripping processes are performed on the surface of the substrate to prepare a superstructure surface with a preset structure.

10. The method for preparing a super surface structure according to claim 9, characterized in that: The metasurface structure is applied to optical detectors.

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