Method for preparing wafer-level nanoimprint photoresist based on molecular layer deposition technology

Abstract

The invention discloses a method for preparing wafer-level nanoimprint photoresist based on a molecular layer deposition technology, and relates to the field of nanoimprint technology and imprint photoresist preparation. The method mainly comprises the following steps that the surface of a substrate is cleaned through oxygen-argon mixed plasma, the substrate is placed in a reaction cavity of MLD equipment, a metal source and an organic source are preheated, the reaction cavity and a gas pipeline are preheated to the reaction temperature, and each MLD cycle comprises the steps of metal source introduction and nitrogen purging, organic source introduction and nitrogen purging. The thickness of the deposited nanoimprint glue is controlled by the number of cycles, after deposition is finished, cooling and taking out the silicon wafer, putting the silicon wafer into nanoimprint equipment, heating the carrying table to 100-180 DEG C, and carrying out ultraviolet light-assisted nanoimprint. By accurately controlling the deposition process of the molecular level, the nanoimprint adhesive with high uniformity, controllable thickness and excellent molecular structure is prepared by using the MLD technology, so that the film forming uniformity is improved, the film thickness is accurately controlled, and the imprint defect is reduced.

Description

Technical Field

[0001] The invention relates to the technical field of nanoimprinting, and in particular to a method for preparing wafer-level nanoimprinting photoresist by using molecular layer deposition technology. Background Art

[0002] As a precise thin film deposition method, molecular layer deposition (MLD) has received extensive attention in the field of nanotechnology in recent years. By precisely controlling the deposition process of a single molecular layer, it can achieve the preparation of ultra-thin, uniform, and structure-controlled thin films, and has great potential in nanoimprint lithography (NIL), which requires high precision. Nanoimprint lithography has gradually become one of the important means of high-precision nanomanufacturing due to its manufacturing capabilities within the sub-10 nanometer resolution range.

[0003] Nanoimprint photoresist is a key factor in improving the resolution and fidelity of the pattern. In the existing technical path, nanoimprint glue is usually an organic polymer material, and is formed into a film by methods such as solution spin coating (for example, the published patents CN118853064A and CN117539125B). However, these methods often have certain problems in the control of molecular-level film thickness accuracy and film thickness consistency. For example, the film thickness uniformity is poor, and it is necessary to determine the spin coating curve through repeated experiments to control the film thickness. The tiny bubbles generated during the spin coating process are difficult to eliminate, which affects the morphology of the final imprinted pattern and causes defects. At present, the optimization of such problems mainly involves changing the imprint glue formula, treating the glue before dripping the imprint glue, and improving the cleanliness of the laboratory. The present invention proposes a different technical route, that is, to achieve dry preparation of nanoimprint photoresist by MLD.

[0004] MLD, with its precise control at the molecular level, can deposit and construct materials at the molecular scale, providing a new idea for the preparation of nanoimprint adhesives. MLD can also effectively adjust the physical and chemical properties of the adhesive film, such as adhesion, optical transparency and mechanical strength, which are crucial to the accuracy of the imprinting process, the repeatability of the mold and the quality of the finished product. In addition, with the continuous improvement of nanoimprint resolution, how to reduce pattern defects has become a key issue in the application. MLD growth of nanoimprint photoresist effectively avoids the wet process of traditional spin coating photoresist, which can significantly reduce the generation of defects such as bubbles and particles during the imprinting process, and improve the repeatability and imprinting accuracy of the mold. Based on the currently proposed technical path, it is expected that MLD and nanoimprint vacuum interconnection equipment will be further developed in the future, so that the entire process of MLD and imprinting can be completed in a vacuum chamber without contact with the outside air, so as to further reduce defects. Summary of the invention

[0005] The object of the present invention is to provide a method for preparing a nanoimprint resist based on the MLD technology. This method precisely controls the deposition process at the molecular level and uses the MLD technology to prepare a nanoimprint resist with high uniformity, controllable thickness, and excellent molecular structure, aiming to improve the film-forming uniformity, precise film thickness control, and reduce imprint defects.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A method for preparing a nanoimprint resist based on the MLD technology, comprising the following steps:

[0008] 1. Place the substrate material in a plasma etching machine and clean the surface of the substrate material with an oxygen-argon mixed plasma.

[0009] 2. Place the cleaned substrate material in the reaction chamber of the MLD equipment, evacuate the air and introduce 10 - 50 sccm of high-purity inert gas to purge the reaction chamber, heat the metal source to 25 - 160 °C, heat the organic source to 25 - 150 °C, and heat the reaction chamber to 100 - 240 °C; in this step, the preheating temperature of the metal source and the organic source depends on the specific physical and chemical properties of the source.

[0010] 3. When the reaction sources and the chamber are heated to the specified temperature and the system pressure reaches 0 - 20 Pa, maintain for 30 - 50 min until the temperature field is stable.

[0011] 4. Each MLD cycle is: introducing the metal source, purging with the carrier gas, introducing the organic source, and purging with nitrogen; this step is a set of reaction cycles, that is, growing a molecular layer of nanoimprint resist, and the thickness of the deposited nanoimprint resist is controlled by the number of cycles.

[0012] 5. After the deposition is completed, wait for the chamber to cool to room temperature, take out the substrate material, and place it in the nanoimprint equipment.

[0013] 6. Heat the stage to 100 - 180 °C and perform ultraviolet-assisted nanoimprinting.

[0014] The metal source in step 2 is one of metal aluminum, hafnium, zinc, tin, indium, bismuth metal precursors or yttrium, erbium rare earth metal precursors.

[0015] The organic source in step 2 is one or more of ethylene glycol, propylene glycol, glycerol, butylene glycol or its isomers, butenediol or its isomers, pentenediol or its isomers, hexenediol or its isomers, heptenediol or its isomers, octenediol or its isomers, phenol, dithiol.

[0016] The substrate material described in the present invention includes, but is not limited to, one of silicon, silicon oxide, quartz glass, soda-lime glass, silicon nitride, silicon carbide.

[0017] Step 4 only describes the MLD process used in the present invention. By replacing different types of metal sources and organic sources, and adjusting the growth process and cycle process, nanoimprint resists with different physical and chemical properties can be obtained.

[0018] The technical effects achieved by the present invention are as follows: Since the MLD technology can precisely control the molecular layer deposition, the precise stacking of each molecular unit enables the imprint resist to have the potential to achieve ultra-high-resolution patterns; the self-limiting deposition process ensures the uniform thickness of the imprint resist, and the molecular structure of each layer can be adjusted according to requirements, such as easily achieving a certain proportion of doping and periodic structures, improving the forming accuracy, flexibility, and stability. In the MLD technology of the present invention, a variety of precursor material combinations can be selected to flexibly adjust the physical and chemical properties of the resist material, so as to adapt to different imprinting requirements. By optimizing the deposition conditions and post-treatment processes, the whole process of the present invention realizes a fully dry process for nanoimprinting, without involving any wet process, which can effectively reduce the generation of defects such as bubbles and particles during the imprinting process, improve the repeatability of the mold and the imprinting accuracy, and at the same time has a supporting and reference significance for the research and development of subsequent vacuum-interconnected MLD nanoimprinting equipment. Description of the Drawings

[0019] Figure 1 is a flowchart of the process, where 1 and 2 are the schematics of the reaction sources used in the molecular layer deposition process, 3 is the nanoimprint lithography resist obtained by deposition, 4 is the substrate, 5 is the mold used in the imprinting process, and the up and down arrows indicate the imprinting and demolding processes. Specific Embodiment Method

[0021] The following further elaborates on the present invention in combination with specific embodiments, but the present invention includes but is not limited to the following embodiments. The methods are all conventional methods unless otherwise specified, and the raw materials are all available from public commercial channels unless otherwise specified. Referring to the attached Figure 1 , the present invention first grew a layer of nanoimprint lithography resist on the cleaned substrate by the MLD method, and then used thermal-assisted ultraviolet nanoimprinting to press the structure in the mold into the resist layer to achieve a fully dry process. The embodiments are as follows:

[0022] Example 1:

[0023] Put the silicon wafer cleaned by oxygen-argon mixed plasma into the MLD reaction chamber, evacuate the chamber, and introduce 25 sccm of high-purity nitrogen. At this time, the background pressure is about 20 Pa. Heat the reaction chamber to 105 °C for preheating. Keep the diethylzinc source at room temperature of 25 °C, heat the ethylene glycol source to 90 °C, and preheat for 50 minutes until the temperature field is stable. Then start deposition, and keep the carrier gas flowing in and the heating for heat preservation during the deposition process. The single cycle step of MLD is: introduce diethylzinc for 50 ms, purge with nitrogen for 30 s, introduce ethylene glycol for 3000 ms, and purge with nitrogen for 90 s. The deposition process is carried out at a chamber pressure of 15 Pa, and 600 cycles are deposited with a thickness of 15 nm. Put the silicon wafer with the grown nanoimprint resist into the imprinting equipment, heat the sample stage to 120 °C, set the ultraviolet light irradiation time to 150 s, and carry out imprinting. The selected imprinting mold is a grating structure with a period of 150 - 500 nm.

[0024] Example 2:

[0025] Put the quartz glass cleaned by oxygen-argon mixed plasma into the MLD reaction chamber, evacuate the chamber, and introduce 20 sccm of high-purity nitrogen. At this time, the background pressure is about 15 Pa. Heat the reaction chamber to 90 °C for preheating. Heat the trimethylaluminum source to room temperature of 25 °C, heat the 1,4-butanediol source to 85 °C, and preheat for 50 minutes until the temperature field is stable. Then start deposition, and keep nitrogen flowing in and the heating for heat preservation during the deposition process. The single cycle step of MLD is: introduce trimethylaluminum for 50 ms, purge with nitrogen for 25 s, introduce 1,4-butanediol for 125 ms, and purge with nitrogen for 25 s. 400 cycles are deposited with a thickness of 32 nm. Put the quartz glass with the grown nanoimprint resist into the imprinting equipment, heat the sample stage to 100 °C, set the ultraviolet light irradiation time to 180 s, and carry out imprinting. The selected imprinting mold is a grating structure with a period of 150 - 500 nm.

[0026] Example 3:

[0027] Put the silicon wafer cleaned by oxygen-argon mixed plasma into the MLD reaction chamber, evacuate the chamber, and introduce 25 sccm of high-purity nitrogen. At this time, the background pressure is about 20 Pa. Heat the reaction chamber to 100 °C for preheating. Heat the tetrakis(dimethylamino)tin source to 70 °C, heat the 1,4-butanediol source to 85 °C, heat the reaction chamber to 100 °C, and preheat for 50 minutes until the temperature field is stable. Then start deposition, and the single cycle step of the deposition process is: introduce tetrakis(dimethylamino)tin for 75 ms, purge with nitrogen for 25 s, introduce 1,4-butanediol for 300 ms, and purge with nitrogen for 45 s. 600 cycles are deposited with a thickness of 30 nm. Put the silicon wafer with the grown nanoimprint resist into the imprinting equipment, heat the sample stage to 180 °C, and carry out imprinting. The selected imprinting mold is a grating structure with a period of 150 - 500 nm.

[0028] Comparative Example:

[0029] The following presents a currently commonly used experimental method that is different from the technical route of the present invention.

[0030] The silicon wafer after being cleaned with an oxygen-argon mixed plasma is placed in a spin-coating device. 5 ml of nanoimprint lithography resist is dropped at the center of the substrate surface, and the spin-coating process is started. The specific parameters are as follows: spin-coating at 500 r / min for 10 s, spin-coating at 3000 r / min for 60 s. The substrate is taken out and placed on a hot plate preheated to 130 °C and heated and baked for 1 min. The substrate is placed in an imprinting device for imprinting. The selected imprinting mold is a grating structure with a period of 150 - 500 nm. Compared with the examples, tiny bubbles can be seen in some areas on the surface of the comparative example under an optical microscope, and the surface roughness and uniformity are lower than those of the examples.

[0031] Based on the above description, the present invention proposes the combination of MLD technology and nanoimprint technology to complete the preparation of dry nanoimprint lithography resist and the realization of imprinting. The MLD technology can select a variety of precursor materials to flexibly adjust the chemical properties of the resist material to meet different imprinting requirements. The above embodiments of the present invention do not cover all the selections of the technical solutions of the present invention. For example, the metal source is not limited to the specific metal source in the examples, and can be selected from metal precursors such as zinc, aluminum, hafnium, tin, indium, bismuth, or rare earth metal precursors such as yttrium and erbium. The organic source is also not limited to those in the examples, and can be selected from one or several of ethylene glycol, propylene glycol, glycerol, butanediol or its isomers; butenediol or its isomers; pentenediol or its isomers; hexenediol or its isomers; heptenediol and / or its isomers; octenediol or its isomers; phenol, dithiols. Similarly, the substrate material of the present invention is not limited to one of silicon, silicon oxide, soda-lime glass, silicon nitride, and silicon carbide. The setting of the MLD deposition conditions and the imprinting conditions in the imprinting device after deposition of the present invention can also be selected within the technical solutions of the present invention, and the specific condition settings achieve the same technical effects as those in the examples.

[0032] It should be further noted that the above embodiments are only used for understanding the technical solutions of the present invention and are not used to limit the protection scope of the present invention. Any obvious adjustment and improvement made to the technical solutions of the present invention that belong to the technical concept of the present invention should also fall within the protection scope of the present invention.

Claims

1. A method for preparing wafer-level nanoimprint photoresist based on molecular layer deposition technology, comprising the following steps: (1) placing the substrate material into a plasma etcher and cleaning the surface of the substrate material with oxygen-argon mixed plasma; (2) placing the cleaned substrate material into the reaction chamber of the MLD equipment, evacuating the chamber and introducing a carrier gas, preheating the metal source and the organic source, and preheating the reaction chamber and the gas pipeline to the reaction temperature; wherein the carrier gas is nitrogen or argon; (3) After the reaction source and the chamber are heated to the specified temperature, maintain it for a certain period of time until the temperature field stabilizes; (4) The reaction process of growing the nanoimprint glue is as follows: introducing a metal source for several seconds; purging the metal source with a carrier gas; introducing an organic source for several seconds; purging the organic source with a carrier gas; (5) After the deposition is completed and the chamber is cooled to room temperature, the substrate material on which the nanoimprint glue is grown is taken out and placed in the nanoimprint equipment; (6) heating the carrier to perform ultraviolet-assisted nanoimprinting; The thickness of the deposited nanoimprint glue is controlled by repeatedly cycling the reaction process of step (4).

2. The method for preparing nanoimprint glue based on MLD technology according to claim 1, characterized in that: The metal source in step (2) is one or more of zinc, aluminum, hafnium, tin, tin, indium, bismuth metal precursors or yttrium, erbium rare earth metal precursors.

3. The method according to claim 1, characterized in that: The organic source in step (2) is one or more of ethylene glycol, propylene glycol, glycerol, butanediol or its isomers; butene glycol or its isomers; pentene glycol or its isomers; hexene glycol or its isomers; heptene glycol and / or its isomers; octenediol or its isomers; phenol, dithiol.

4. The method according to claim 1, characterized in that: The substrate material includes, but is not limited to, one of silicon, silicon oxide, quartz glass, soda-lime glass, silicon nitride, and silicon carbide.

5. The method according to claim 1, characterized in that: In step (2), the carrier gas flow rate is 10-50sccm, the metal source preheating temperature is 25-160°C, the organic source is heated to 25-150°C, the reaction chamber is heated to 100-240°C, and the chamber pressure is maintained at 0-20Pa without carrier gas for 30-50min until the temperature field stabilizes.

6. The method according to claim 1, characterized in that: In step (6), the stage is heated to 100-180° C. and ultraviolet-assisted nanoimprinting is performed.

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