Photoetching method for preparing pattern edge frame structure in one step

Abstract

The invention belongs to the technical field of micro-nano machining and photoetching, and particularly relates to a photoetching method for preparing a pattern edge frame structure in one step. After a photoresist containing a photoacid generator, a polymer and a solvent is coated to form a film, single exposure is performed through a mask, and three characteristic areas are spontaneously formed in the film according to acid concentration distribution: the acid concentration in the exposure area is the highest, the polymer is triggered to be crosslinked and then hydrolyzed, and the polymer is soluble during development; in the edge region influenced by acid diffusion in the unexposed region, the polymer is only crosslinked and is insoluble during development; the core area, which is not influenced by acid diffusion, in the unexposed area is soluble during development. And after developing, synchronously removing the soluble region and retaining the insoluble region, thereby directly forming the pattern edge frame structure in one step. The method is simple in process, does not need multi-step exposure or complex post-processing, can regulate and control the structure morphology in a programmed manner, and is suitable for the fields of micro electro mechanical systems, photonic devices, programmable photoetching and the like.

Description

Technical Field

[0001] This application belongs to the field of microelectronic device fabrication technology, and more specifically, relates to a photolithography method for preparing patterned edge frame structures in one step. Background Technology

[0002] Fine patterning at the micro- and nanoscale is fundamental to fields such as semiconductors, microelectromechanical systems (MEMS), photonic devices, and advanced packaging. Photolithography, as the core method of patterning, uses photoresist (photoresist as its key material), which is mainly classified into positive and negative photoresists based on the relationship between the pattern and the photomask after development.

[0003] In recent years, to improve process flexibility, "positive-negative reversal" or "dual-tone" photoresists have emerged. These materials can obtain positive or negative patterns on the same coating layer by changing exposure or post-processing conditions. However, most existing reversal techniques still follow the mask pattern replication model and typically rely on complex multi-step processes. For example, low-dose exposure and baking to form a latent image, followed by full exposure and differential development, requires precisely controlled multiple exposures and additional post-exposure baking steps. These numerous process steps and sensitive control parameters (such as baking temperature and time) increase process complexity and cost, impose additional requirements on equipment, and limit processing efficiency and stability.

[0004] Of particular note is the need to obtain mask pattern edge framework structures that go beyond simple geometric replication in the fabrication of functional micro / nano devices (such as optical resonators, sensors, and metamaterial units). These include isolated ring-shaped, frame-like, or dam-like edge structures. Fabricating such pattern edge framework structures using traditional photolithography presents fundamental challenges: conventional positive or negative photoresist processes require the design and fabrication of complex masks that perfectly correspond to the geometry, resulting in high costs; attempting to combine multiple masks through multiple photolithography and overlay processes leads to low process integration and extremely high overlay precision, making yield difficult to guarantee; while grayscale masks or electron beam direct writing techniques can achieve this, the equipment is expensive and inefficient.

[0005] Therefore, there is an urgent need in this field for a photolithography method that does not require complex masks or multi-step overlay processes, is simple and efficient, requires no complicated post-processing steps, and can directly form the edge framework structure of a pattern from a basic mask pattern in one step. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the purpose of this application is to provide a one-step photolithography method for fabricating patterned edge frame structures. This method aims to solve the problems of existing positive and negative reversal photolithography being limited by mask replication mode and unable to realize the transformation from mask pattern to patterned edge frame structure, as well as the complex process of fabricating patterned edge frame structures, which requires multiple photolithography, etching or complex grayscale mask techniques, and has low process integration and high overlay accuracy requirements.

[0007] To achieve the above objectives, in a first aspect, this application provides a photolithography method for preparing a patterned edge framework structure in one step, comprising the following steps: S1. A photoetchant is applied to the substrate surface to form a thin film; The aforementioned photoresist includes a photoacid generator, a polymer, and a solvent; the aforementioned photoacid generator is a photoacid generator capable of producing protic acid under irradiation; the aforementioned polymer contains cationic crosslinking groups that can be initiated into a crosslinking reaction by the aforementioned protic acid, and the formed crosslinking structure can undergo hydrolytic cleavage under further catalysis of the protic acid; S2. Under the cover of a photomask, the above-mentioned thin film is subjected to a single exposure, the exposure dose being configured to cause the above-mentioned thin film to produce the following zoned chemical reactions: (a) In the exposed area, the protic acid generated by the photoacid generator initiates cross-linking of the polymer and subsequently undergoes acid-catalyzed hydrolysis, making the area soluble in subsequent development; (b) In the edge region of the unexposed region adjacent to the above-mentioned exposed region, the polymer in the edge region is affected by the protic acid diffused from the exposed region, and only cross-linking reaction occurs, making the region insoluble in subsequent development; (c) In the unexposed area far from the above-mentioned exposure area, the film material is not affected by the diffusion of protic acid and does not undergo a chemical reaction, making the area soluble in subsequent development; S3. The film exposed in step S2 is placed in a developing solution for a first development, which simultaneously dissolves the exposed area and the unexposed area that is not affected by the diffusion of protic acid, while retaining the edge area of ​​the unexposed area, thereby directly forming a pattern edge frame structure.

[0008] Preferably, the polymer is poly2,3-dihydrofuran with a number-average molecular weight of 100,000 to 300,000.

[0009] Preferably, the above-mentioned photoacid-generating agent is one or more of iodonium salt, sulfonium salt, o-nitrobenzyl sulfonate, iminosulfonate, and N-hydroxyiminosulfonate.

[0010] Preferably, the solvent is one or more of ethyl acetate, propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, tetrahydrofuran, cyclohexanone, toluene, dimethyl sulfoxide, ethyl lactate, n-heptane, butyl acetate, and γ-butyrolactone.

[0011] Preferably, the amount of the polymer used is 1 wt% to 10 wt% of the mass of the solvent.

[0012] Preferably, the amount of the above-mentioned photoacid-generating agent is 10wt% to 40wt% of the polymer mass.

[0013] Preferably, in step S2, before exposure, the film is baked at 90°C to 120°C for 1 min to 2 min.

[0014] Preferably, in step S2, the dose of a single exposure is 300 mJ / cm². 2 ~2000mJ / cm 2 .

[0015] Preferably, in step S3, the developing solution is ethyl acetate.

[0016] Secondly, this application provides a graphic edge frame structure, which is prepared using the above-mentioned photolithography method.

[0017] Thirdly, this application provides a micro / nano device comprising the above-described patterned edge frame structure.

[0018] In summary, the technical solutions conceived in this application have the following main technical advantages compared with the prior art: (1) Existing technologies for fabricating patterned edge framework structures typically rely on complex processes such as multiple photolithography, etching, or grayscale masking. This application utilizes a photoresist with specific components, requiring only a single exposure to spontaneously form three regionalized reactions within the thin film through acid diffusion: the exposed region: due to the high acid concentration, the polymer undergoes cross-linking followed by hydrolysis, making it soluble during development; the edge of the unexposed region adjacent to the exposed region: affected by the proton acid diffused from the exposed region, the polymer in this edge region only undergoes cross-linking, making it insoluble during development; the unexposed region far from the exposed region: not affected by proton acid diffusion, making it soluble during development. After development, the soluble region is simultaneously removed, leaving only the edge region of the insoluble unexposed region, thus directly forming the patterned edge framework structure in one step. This method avoids additional post-processing steps such as reverse baking, full exposure, or multiple developments after exposure, greatly simplifying the process flow and reducing integration difficulty, which is beneficial for reducing manufacturing costs and improving process stability.

[0019] (2) By adjusting parameters such as the molecular weight and amount of polymer in the photoresist, the type and concentration of photoacid generator, and the exposure dose, this application can precisely control the acid diffusion distance and reaction degree, thereby realizing flexible design and programmed customization of the line width, height and morphology of the pattern edge frame structure, and adapting to the manufacturing needs of various micro and nano devices.

[0020] (3) The patterned edge framework structure formed by the photolithography method provided in this application has the characteristics of clear edges, controllable linewidth (up to submicron scale), and high resolution, which can meet the manufacturing requirements of high-performance micro and nano devices. At the same time, the photoresist system used has good compatibility with existing semiconductor processes, and the high-quality patterned edge framework structure prepared has broad application potential in cutting-edge fields such as photonic crystals, integrated sensors, microfluidic chips, and radio frequency MEMS devices. Attached Figure Description

[0021] Figure 1 It is the pattern of the mask used in Embodiment 1 of this application; Figure 2 This is a metallographic microscope image of the graphic edge frame structure obtained in Embodiment 1 of this application; Figure 3 These are metallographic microscope images of the graphic edge frame structure obtained by changing the exposure time in embodiments 2-5 of this application. Detailed Implementation

[0022] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0023] In the description of this application, it should be understood that the term "and / or" describes a relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, or B existing alone. The symbol " / " in this document indicates that the related objects are in an "or" relationship; for example, A / B means A or B.

[0024] In the description of the embodiments in this application, the words "exemplary" or "for example" are used to indicate that they are examples, illustrations, or descriptions. Any embodiment or design that is described as "exemplary" or "for example" in the embodiments of this application should not be construed as being more preferred or advantageous than other embodiments or design options. Specifically, the use of the words "exemplary" or "for example" is intended to present the relevant concepts in a specific manner.

[0025] In the description of the embodiments of this application, unless otherwise stated, "multiple" means two or more.

[0026] In this application, "graphic edge frame structure" refers to a hollow frame structure formed on a substrate after development using photolithography, consisting only of annular regions corresponding to the edges of the graphic entity in the photomask. This structure is a physical representation and representation of the edge portion of the graphic entity in the photomask. For example, the graphic edge frame structure can be annular, frame-shaped, etc.

[0027] This application provides a photolithography method for fabricating a patterned edge frame structure, comprising the following steps: S1. Apply the photoetching agent used in the above-mentioned applications to the substrate surface to form a thin film; The aforementioned photoresist includes a polymer, a photoacid generator, and a solvent; the aforementioned photoacid generator is a photoacid generator capable of producing protonic acid under irradiation; the aforementioned polymer contains cationic crosslinking groups that can be initiated by protonic acid to undergo crosslinking reactions, and the formed crosslinking structure can undergo hydrolytic cleavage under further catalysis of protonic acid; S2. Under the cover of a photomask, the above-mentioned thin film is subjected to a single exposure, the exposure dose being configured to cause the above-mentioned thin film to produce the following zoned chemical reactions: (a) In the exposed area, the protic acid generated by the photoacid generator in the photoetchant initiates cross-linking of the polymer in the photoetchant and subsequently undergoes acid-catalyzed hydrolysis, making the area soluble in subsequent development; (b) In the edge region of the unexposed region adjacent to the above-mentioned exposed region, the polymer in the edge region is affected by the protic acid diffused from the exposed region, and only cross-linking reaction occurs, making the region insoluble in subsequent development; (c) In the unexposed area far from the above-mentioned exposure area, the film material is not affected by the diffusion of protic acid and does not undergo a chemical reaction, making the area soluble in subsequent development; S3. The film exposed in step S2 is placed in a developing solution for a first development, which simultaneously dissolves the exposed area and the unexposed area that is not affected by the diffusion of protic acid, while retaining the edge area of ​​the unexposed area, thereby directly forming a pattern edge frame structure.

[0028] During the experiment, the inventors unexpectedly discovered that by subjecting the photoresist of the above-mentioned specific components to a single high-dose mask exposure, the spatial diffusion gradient of the acid generated by the exposure can be used to guide differentiated cross-linking and acid-catalyzed hydrolysis reactions within the region, thereby generating a graphic edge framework structure corresponding to the mask pattern in one go and directly.

[0029] In some embodiments, the polymer is poly2,3-dihydrofuran with a number average molecular weight of 100,000 to 300,000. In some embodiments, the amount of the polymer used is 1 wt% to 10 wt% of the solvent mass.

[0030] This application does not limit the source of the aforementioned poly2,3-dihydrofuran; it can be purchased from commercially available products or prepared in a laboratory. For example, the preparation method of the aforementioned poly2,3-dihydrofuran can be as follows: G3 catalyst and 2,3-dihydrofuran are mixed at room temperature and allowed to stand. Then, dichloromethane is added to completely dissolve the mixture. The completely dissolved mixture is then filtered and added dropwise to ethanol to obtain a precipitate, which is poly2,3-dihydrofuran. Those skilled in the art can obtain poly2,3-dihydrofurans with different number-average molecular weights by adjusting the ratio of the raw materials.

[0031] In some embodiments, the photoacid generator is one or more selected from iodonium salt, sulfonium salt, o-nitrobenzyl sulfonate, iminosulfonate, and N-hydroxyiminosulfonate. In some embodiments, the amount of the photoacid generator is 10wt% to 40wt% of the polymer mass.

[0032] In some embodiments, the solvent is any organic solvent capable of dissolving the polymer and the photoacid generator, including but not limited to one or more of ethyl acetate, propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, tetrahydrofuran, cyclohexanone, toluene, dimethyl sulfoxide, ethyl lactate, n-heptane, butyl acetate, and γ-butyrolactone.

[0033] In some embodiments, before exposure in step S2, the film is baked at 90°C to 120°C for 1 min to 2 min.

[0034] In some embodiments, in step S2, the exposure dose is 300 mJ / cm². 2 ~2000mJ / cm 2 .

[0035] In some embodiments, in step S3, the developing solution is ethyl acetate.

[0036] On the other hand, this application also provides a graphic edge frame structure, which is prepared by the above-mentioned photolithography method.

[0037] This application also provides a micro / nano device comprising the above-described patterned edge frame structure.

[0038] It should be understood that materials of the same or similar type, model, quality, properties, or function as the reagents and instruments used in the following embodiments can be used to implement this application. Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods. Unless otherwise specified, the materials and reagents used in the following embodiments are commercially available.

[0039] The following is an example: Example 1 The photolithography method for preparing a patterned edge framework structure in one step provided in this embodiment includes the following steps: (1) Preparation of photoresist A photoresist was obtained by uniformly mixing a polymer (poly-2,3-dihydrofuran with a number-average molecular weight of approximately 170,000), a photoacid generator (4,5-dimethoxy-2-nitrobenzyl p-toluenesulfonic acid), and a solvent (ethyl acetate). Specifically, the amount of poly-2,3-dihydrofuran in the photoresist was 1.5% of the solvent mass, and the amount of the photoacid generator was 30% of the poly-2,3-dihydrofuran mass.

[0040] The preparation method of the above-mentioned poly(2,3-dihydrofuran) is as follows: G3 catalyst (0.003 g, 0.0034 mmol) and 2,3-dihydrofuran (3 g, 42.8 mmol) are stirred and mixed at room temperature for 1 min, and then allowed to stand for 10 min to obtain a rubbery mixture. Next, 80 mL of dichloromethane is added, and the mixture is allowed to stand for 24 h to allow it to dissolve completely. The completely dissolved mixture is filtered through a 0.22 μm filter, and then added dropwise to ethanol to precipitate poly(2,3-dihydrofuran) with a number average molecular weight of approximately 170,000.

[0041] (2) Single high-dose exposure The aforementioned photoresist was spin-coated onto a clean silicon wafer and baked at 70°C for 30 seconds to obtain a photoresist film. Then, a single high-dose exposure was performed on the film using a 365nm lithography machine with a mask, wherein the mask pattern is as follows: Figure 1 As shown, the minimum feature size of a single pattern on the mask is 3 μm, and the exposure dose is 660 mJ / cm². 2 In the photoresist film of the exposed area, the photoacid generator produces protic acid under light irradiation, which induces cationic crosslinking of the double bond structure in the polymer. This causes partial crosslinking of the polymer in the exposed area, forming crosslinked products insoluble in the solvent, thus making the exposed area insoluble in the solvent. As the concentration of protic acid increases, on the one hand, the protic acid generated in the exposed area catalyzes the hydrolysis of the vinyl ether structure of the remaining unreacted polymer, causing the partially crosslinked polymer in the exposed area to hydrolyze and its polarity to increase, thus making the exposed area soluble in alcohol solvents. On the other hand, the protic acid generated in the exposed area diffuses from the exposed area to the unexposed area. In the edge regions of the unexposed area affected by acid diffusion, the polymer in these regions undergoes partial crosslinking, forming crosslinked products insoluble in the solvent. However, in the unexposed areas not affected by acid diffusion (far from the exposed area), the film material does not undergo chemical reaction, and the solubility in these regions remains unchanged, still soluble in the solvent.

[0042] (3) Development yields the edge frame structure of the graphic. The film, after high-dose exposure, is developed in ethyl acetate for 30 seconds, simultaneously dissolving the exposed and unexposed areas that are unaffected by acid diffusion, while retaining the edge areas in the unexposed areas affected by acid diffusion. This directly forms a pattern edge framework structure with a square ring topology corresponding to the mask pattern. Figure 2 As shown, the line width of the graphic edge frame structure is 6.6 μm.

[0043] Examples 2-5 In Examples 2-5 of this application, the photolithography method of Example 1 is used to prepare the patterned edge framework structure in one step. The minimum feature size of a single pattern on the mask is 10 μm. The differences in the process are shown in Table 1. The resulting patterned edge framework structure is as follows: Figure 3 As shown (scale bar is 50μm).

[0044] Table 1. Process parameters for fabricating graphic edge frame structures and linewidths of the resulting graphic edge frame structures.

[0045] Experimental results show (Table 1, Figure 3 As the exposure dose increases, the line width of the resulting graphic edge frame structure gradually increases, indicating that this application can programmatically define the graphic edge frame structure obtained by adjusting the exposure dose.

[0046] The photolithography method provided in this application is applicable to grayscale / dose-encoded patterning, chemically programmable lithography, fabrication of microstructures / micro-optical devices, and other micro-nano fabrication fields requiring highly flexible pattern design, providing an important technical path for novel adaptive and programmable lithography materials and processes.

[0047] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A photolithographic method for fabricating a patterned edge framework structure in one step, characterized in that, Includes the following steps: S1. A photoetchant is applied to the substrate surface to form a thin film; The photoresist includes a photoacid generator, a polymer, and a solvent; the photoacid generator is a photoacid generator capable of producing protic acid under irradiation; the polymer contains cationic crosslinking groups that can be initiated by the protic acid to crosslink, and the formed crosslinking structure can undergo hydrolytic cleavage under further catalysis of the protic acid; S2. Under the cover of a photomask, the film is subjected to a single exposure, the exposure dose being configured to cause the film to undergo the following zoned chemical reactions: (a) In the exposed area, the protic acid generated by the photoacid generator initiates cross-linking of the polymer and subsequently undergoes acid-catalyzed hydrolysis, making the area soluble in subsequent development; (b) In the edge region of the unexposed region adjacent to the exposed region, the polymer in the edge region is affected by the protic acid diffused from the exposed region, and only cross-linking reaction occurs, making the region insoluble in subsequent development; (c) In the unexposed area far from the exposed area, the film material is not affected by the diffusion of protic acid and does not undergo a chemical reaction, making the area soluble in subsequent development; S3. The film exposed in step S2 is placed in a developing solution for a first development, which simultaneously dissolves the exposed area and the unexposed area that is not affected by the diffusion of proton acid, while retaining the edge area of ​​the unexposed area, thereby directly forming a graphic edge frame structure.

2. The photolithography method according to claim 1, characterized in that, In step S1, the polymer is poly2,3-dihydrofuran with a number-average molecular weight of 100,000 to 300,000.

3. The photolithography method according to claim 1, characterized in that, In step S1, the photoacid-generating agent is one or more of iodonium salt, sulfonium salt, o-nitrobenzyl sulfonate, iminosulfonate, and N-hydroxyiminosulfonate.

4. The photolithography method according to claim 1, characterized in that, In step S1, the solvent is one or more of ethyl acetate, propylene glycol monomethyl ether acetate, propylene glycol monomethyl ether, tetrahydrofuran, cyclohexanone, toluene, dimethyl sulfoxide, ethyl lactate, n-heptane, butyl acetate, and γ-butyrolactone.

5. The photolithography method according to any one of claims 1 to 4, characterized in that, In step S1, the amount of the polymer used is 1wt% to 10wt% of the solvent mass; the amount of the photoacid generator used is 10wt% to 40wt% of the polymer mass.

6. The photolithography method according to claim 1, characterized in that, In step S2, before exposure, the film is baked at 90°C to 120°C for 1 min to 2 min.

7. The photolithography method according to claim 1, characterized in that, In step S2, the dose of the single exposure is 300 mJ / cm². 2 ~2000mJ / cm 2 .

8. The photolithography method according to claim 1, characterized in that, In step S3, the developing solution is ethyl acetate.

9. A graphic edge frame structure, characterized in that, It is prepared using the photolithography method described in any one of claims 1 to 8.

10. A micro / nano device, characterized in that, It includes the graphic edge frame structure as described in claim 9.

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