Photoresist composition with gradient change of crosslinking density and patterning method thereof

Abstract

According to the photoresist composition with the cross-linking density changing in a gradient manner and the patterning method of the photoresist composition, the low-molecular-weight first cross-linking agent and the high-molecular-weight second cross-linking agent are introduced into the photoresist composition, so that the photoresist composition is subjected to cross-linking reaction in the post-exposure baking process for forming a photoetching pattern; the diffusion rate of the first cross-linking agent is greater than that of the second cross-linking agent, so that gradient distribution of cross-linking density in the photoresist film from top to bottom can be realized, reaction rate balance of a developing solution in a permeation process is ensured, occurrence of various defects is greatly reduced, formation of footing defects is effectively inhibited in a positive developing process, and the production efficiency is improved. Compared with the prior art, the metal oxide photoresist composition has the advantages that the metal oxide photoresist composition is adopted, the perpendicularity of a photoetching pattern is ensured, in a negative developing process, bottom residues and T-top defects are avoided, the pattern resolution is remarkably improved, and in addition, 16 nm fine pattern processing can be realized on the basis of the advantages of high sensitivity and resolution of the metal oxide photoresist and in combination with the cross-linking density gradient change of the photoresist composition.

Description

Technical Field

[0001] This invention relates to the field of photoresist technology, and in particular to a photoresist composition with varying crosslinking density and a method for patterning the same. Background Technology

[0002] In the field of integrated circuit manufacturing, photolithography is one of the most critical technologies for achieving high-precision patterning of integrated circuits. Its principle involves using a light source to expose photoresist coated on a substrate wafer, thereby transferring the fine patterns on the photoresist to the substrate wafer. Based on the change in photoresist solubility before and after exposure, photoresists can be divided into positive photoresists and negative photoresists. Positive photoresists experience an increase in solubility after exposure, while negative photoresists experience a decrease in solubility.

[0003] With the continuous shrinking of semiconductor device feature sizes, extreme ultraviolet (EUV) lithography has become a key method for breaking through advanced process nodes due to its advantages such as short wavelength and high resolution. However, the number of EUV photons is limited, and traditional organic chemical amplification photoresists are prone to random effects during exposure, leading to deterioration of linewidth roughness and severely affecting pattern uniformity and device performance. To overcome this bottleneck, metal oxide-based photoresists have received widespread attention in recent years due to their high EUV absorption rate, high sensitivity, low resolution, and excellent etching resistance. However, most existing metal oxide-based photoresists are uniform cross-linked networks, resulting in all photoresist components having the same migration rate during baking, which makes it difficult to achieve uniformity in positive development processes, such as... Figure 1 As shown in (a), when the developer penetrates, the difference in reaction rate between the top 121 and the bottom 122 can easily lead to insufficient development of the bottom 122 or excessive erosion of the sidewalls, forming base defects and damaging the perpendicularity of the photolithographic pattern. In the negative development process 11, as... Figure 1 As shown in (b), due to the overly rapid reaction of the top 121 crosslinking layer, photoresist residue 123 occurs, resulting in T-top defects, which ultimately affect the integrity and resolution of the pattern.

[0004] Therefore, there is an urgent need to develop a metal oxide photoresist with a gradient in crosslinking density, so that the metal oxide photoresist has different crosslinking densities in different regions, so that the developer can achieve a reaction rate balance during the penetration process, thereby obtaining high-resolution patterns with high verticality and few defects.

[0005] It should be noted that the above introduction to the technical background is only for the purpose of providing a clear and complete explanation of the technical solutions of this application and facilitating understanding by those skilled in the art. It should not be assumed that these technical solutions are known to those skilled in the art simply because they have been described in the background section of this application. Summary of the Invention

[0006] In view of the shortcomings of the prior art described above, the purpose of the present invention is to provide a photoresist composition with varying crosslinking density and a method for patterning the same, in order to solve the problems of poor verticality of photolithographic patterns caused by the presence of base defects in metal oxide-based photoresists with uniform crosslinking networks after development, as well as T-top defects caused by bottom residue.

[0007] To achieve the above and other related objectives, the present invention provides a photoresist composition with a crosslinking density gradient, comprising:

[0008] Metal oxide nanoclusters, comprising a metal oxide core and an organic ligand coordinated with the metal oxide core, having the general molecular formula MxOyRmLn, wherein M is a metal element, L is a photosensitive anion or cation ligand, R is a polymerizable organic ligand, and O is an oxygen atom.

[0009] The crosslinking agent includes a first crosslinking agent and a second crosslinking agent, wherein the first crosslinking agent is a low molecular weight crosslinking agent and the second crosslinking agent is a high molecular weight crosslinking agent;

[0010] Photoinitiators and solvents.

[0011] Optionally, M is selected from any one of titanium, tin, zirconium, zinc, copper, iron, cobalt, nickel, silver, and hafnium.

[0012] Optionally, the low molecular weight crosslinking agent includes an acrylic resin or epoxy resin with a molecular weight of less than 300 and possessing bifunctional groups.

[0013] Optionally, the bifunctional acrylic resin includes at least one of ethylene glycol diacrylate, alkyl acrylate, hydroxyl-containing acrylate, polypropylene glycol acrylate, or polytetramethylene glycol acrylate.

[0014] Optionally, the high molecular weight crosslinking agent includes an acrylic resin or epoxy resin with a molecular weight greater than 300 and possessing multiple functional groups.

[0015] Optionally, the multifunctional acrylic resin includes at least one of trimethylolpropane acrylate, pentaerythritol acrylate, alkoxylated glycerol acrylate, or dimeric pentaerythritol acrylate.

[0016] Optionally, the first crosslinking agent accounts for 20% to 50% of the crosslinking agent, and the second crosslinking agent accounts for 50% to 80% of the crosslinking agent.

[0017] Optionally, the solvent is one or more selected from ethyl lactate, butyl acetate, propylene glycol methyl ether acetate, methanol, ethanol, and propanol.

[0018] Optionally, the diffusion rate of the first crosslinking agent is greater than the diffusion rate of the second crosslinking agent.

[0019] The present invention also provides a method for forming a photolithographic pattern, comprising:

[0020] The photoresist composition described above is coated onto the surface of a wafer substrate;

[0021] The wafer substrate is dried to form a photoresist film on the surface of the wafer substrate;

[0022] The photoresist film is exposed and then baked after the exposure.

[0023] The photoresist film is placed in a developer to develop in order to form a photolithographic pattern on the surface of the wafer substrate.

[0024] As described above, the photoresist composition with varying crosslinking density and its patterning method of the present invention have the following advantages compared to the prior art: By introducing a low molecular weight first crosslinking agent and a high molecular weight second crosslinking agent into the photoresist composition, a crosslinking reaction occurs in the photoresist composition during the baking process after exposure to form the photolithographic pattern. Since the diffusion rate of the first crosslinking agent is greater than that of the second crosslinking agent, a gradient distribution of crosslinking density from top to bottom is achieved in the photoresist film, ensuring that the reaction rate is balanced during the penetration of the developer solution during subsequent development, thereby significantly reducing the probability of various defects. Specifically, in the positive development process, the formation of base defects is effectively suppressed, ensuring the verticality of the sidewalls of the photolithographic pattern. In the negative development process, photoresist residue and T-top defects are avoided, significantly improving pattern integrity and resolution. Furthermore, based on the high sensitivity and resolution advantages of metal oxide photoresist itself, combined with the variation of crosslinking density in the photoresist composition, fine pattern processing of 16nm can be achieved. Attached Figure Description

[0025] Figure 1 The diagram shows the structure of a photoresist composition after development in the prior art.

[0026] Figure 2 The diagram shows a cross-linking reaction process of the photoresist composition provided in an embodiment of the present invention.

[0027] Figure 3 The diagram shows a process flow chart of a method for forming a photolithographic pattern according to another embodiment of the present invention.

[0028] Figure 4 The diagram shows a structural schematic of a photolithographic pattern formed using the photoresist composition described in this invention.

[0029] Component designation explanation

[0030] 10. Positive development; 11. Negative development; 121. Top; 122. Bottom; 123. Photoresist residue; 131. First crosslinking agent; 132. Second crosslinking agent; 141. High crosslinking density region; 142. Low crosslinking density region; 15. Negative development process; 151. Top of photoresist film; 152. Bottom of photoresist film; S1~S4, steps. Detailed Implementation

[0031] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention, and the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

[0032] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0033] Example 1

[0034] This invention provides a photoresist composition comprising: metal oxide nanoclusters, a crosslinking agent, a photoinitiator, and a solvent.

[0035] The metal oxide nanoclusters comprise a metal oxide core and an organic ligand coordinated with the metal oxide core, and have the general molecular formula MxOyRmLn, where M is a metal element, L is a photosensitive anion or cation ligand, R is a polymerizable organic ligand, and O is an oxygen atom.

[0036] As an example, the metal oxide nanoclusters are 50 to 150 parts by weight, the crosslinking agent is 5 to 50 parts by weight, the photoinitiator is 0.1 to 5 parts by weight, and the organic solvent is 100 to 1000 parts by weight.

[0037] The photoresist composition provided in this invention uses metal oxide nanoclusters as the main material of the photoresist, and adds photosensitive anionic and cationic ligands and crosslinking agents. The photosensitive anionic and cationic ligands are generally photoacid generators, which can generate photoacids under photon irradiation. Under the post-baking process conditions, the photoacids can induce the crosslinking agent to undergo a crosslinking reaction with the functional groups on the metal oxide nanoclusters. In addition, the added photoinitiator can generate free radicals after exposure. The free radicals will also induce the metal oxide nanoclusters to undergo a crosslinking reaction with the crosslinking agent during the post-baking process, thereby obtaining a photolithographic pattern of the desired shape after development.

[0038] In the general molecular formula MxOyRmLn of the metal oxide nanoclusters, M can be selected from any one of titanium, tin, zirconium, zinc, copper, iron, cobalt, nickel, silver, and hafnium, preferably titanium. The metal oxide nanoclusters can be titanium oxide, tin oxide, zirconium oxide, zinc oxide, copper oxide, iron oxide, cobalt oxide, nickel oxide, silver oxide, and hafnium oxide. The metal oxide nanoclusters have a high absorption rate for ultraviolet light, effectively improving energy utilization and resulting in higher energy absorption in the photoresist. This allows for more effective initiation of cross-linking reactions between free radicals or photoacids and cross-linking agents, thereby improving photosensitivity. Furthermore, the presence of the metal oxides also improves the etch resistance of the photoresist.

[0039] In the general molecular formula MxOyRmLn of the metal oxide nanoclusters, 4≤x≤12, 6≤y≤12, 1≤m≤2, and 4≤n≤24, where x can be any even number from 4 to 12, such as 4, 6, 8, 10, or 12; y can be any integer from 6 to 12, such as 6, 7, 8, 9, 10, 11, or 12; m can be any integer from 1≤m≤2, such as 1 or 2; and n can be any integer from 4 to 24, such as 4, 8, 12, 16, 20, or 24.

[0040] The crosslinking agent includes a first crosslinking agent 131 and a second crosslinking agent 132, wherein the first crosslinking agent 131 is a low molecular weight crosslinking agent and the second crosslinking agent 132 is a high molecular weight crosslinking agent.

[0041] As an example, the low molecular weight crosslinking agent includes an acrylic resin or epoxy resin with a molecular weight of less than 300 and possessing bifunctional groups. These resins have short molecular chains, low viscosity, and a high diffusion coefficient under post-baking conditions. The high molecular weight crosslinking agent includes an acrylic resin or epoxy resin with a molecular weight of greater than 300 and possessing multifunctional groups. These resins have a large molecular structure and a low diffusion coefficient under post-baking conditions. The first crosslinking agent 131 accounts for 20% to 50% of the crosslinking agent, and the second crosslinking agent 132 accounts for 50% to 80%. Because the diffusion rate of the first crosslinking agent 131 is greater than that of the second crosslinking agent 132, the first crosslinking agent 131 is more concentrated on the top layer of the photoresist. The metal oxide nanoclusters and the first crosslinking agent 131 undergo a crosslinking reaction on the top layer of the photoresist. The photoresist forms a high cross-linking density region 141, while the second cross-linking agent 132 is more concentrated on the bottom layer of the photoresist. The metal oxide nanoclusters and the second cross-linking agent 132 react cross-link in the bottom layer of the photoresist to form a low cross-linking density region 142. Thus, in the positive development process, the low cross-linking density region 142 at the bottom 152 of the photoresist film reacts and dissolves faster, while the high cross-linking density region 141 at the top 151 of the photoresist film reacts and dissolves slower, effectively resisting the lateral erosion of the developer and avoiding base defects. In the negative development process 15, the cross-linking network of the high cross-linking density region 141 at the top 151 of the photoresist film can effectively prevent excessive penetration of the developer, while ensuring that the low cross-linking density region 142 at the bottom 152 of the photoresist film reacts and dissolves faster, avoiding bottom residue 122 and T-top defects, and finally obtaining a photolithographic pattern with high verticality.

[0042] As an example, the difunctional acrylic resin includes at least one of ethylene glycol diacrylate, alkyl acrylate, hydroxyl-containing acrylate, polypropylene glycol acrylate, or polytetramethylene glycol acrylate. Each end of the difunctional acrylic resin has an acrylate group that can participate in the photopolymerization reaction, and its molecular weight is small, which ensures rapid migration during the baking process after exposure, and ensures that the acrylate groups in the first crosslinking agent 131 react with photoacids or free radicals.

[0043] As an example, the multifunctional acrylic resin includes at least one of trimethylolpropane acrylate, pentaerythritol acrylate, alkoxylated glycerol acrylate, or dimeric pentaerythritol acrylate. The multifunctional acrylic resin generally has a large molecular weight and has three or more acrylate functional groups. It diffuses slowly during the baking process after exposure and is mainly enriched in the bottom layer region of the photoresist film, ensuring that the acrylate groups in the second crosslinking agent 132 react with photoacids or free radicals.

[0044] As an example, the solvent is one or more selected from ethyl lactate, butyl acetate, propylene glycol methyl ether acetate, methanol, ethanol, and propanol. This ensures that the material can be fully dissolved and form a uniform thin film, guaranteeing high precision and high quality in the photolithography patterning process and preventing film inhomogeneity caused by crystallization. The selection of the above solvents ensures uniform coating of the photoresist.

[0045] In another example, the photoresist composition may further include a leveling agent, a dispersant, or a thickener, wherein the leveling agent can adjust the viscosity and flowability of the photoresist system and increase the uniformity of the photoresist film.

[0046] Example 2

[0047] This embodiment also provides a method for forming photolithographic patterns, such as Figure 3 The diagram shown illustrates the process flow of a method for forming a photolithographic pattern provided in this embodiment. The method includes the following steps:

[0048] S1: Coat the surface of the wafer substrate with the photoresist composition described in Example 1;

[0049] S2: Dry the wafer substrate to form a photoresist film on the surface of the wafer substrate;

[0050] S3: Expose the photoresist film and bake it after exposure;

[0051] S4: The photoresist film is placed in a developer to develop in order to form a photolithographic pattern on the surface of the wafer substrate.

[0052] The method for forming the photolithographic pattern is further described below:

[0053] In step S1, the photoresist composition described in Example 1 is coated on the surface of the wafer substrate.

[0054] Specifically, the wafer substrate is made of materials including, but not limited to, single-crystal silicon, silicon carbide, germanium, sapphire, or gallium nitride, and circuits or transistors are formed on the surface of the wafer substrate. Before coating the photoresist composition, the wafer substrate is inspected, including but not limited to visual inspection, electrical performance inspection, flatness inspection, and size inspection, to ensure that the quality of the wafer substrate meets the requirements of subsequent processing. The inspected wafer substrate is placed on a spin coater tray and its surface is cleaned with a nitrogen gun. Then, the vacuum system is activated to adsorb and fix the wafer substrate on the spin coater tray, and an appropriate amount of photoresist composition is dropped onto the surface of the wafer substrate. For example, the spin coater is started at a speed of 2500 rpm to perform the spin coat operation, forming a photoresist layer on the surface of the wafer substrate. During this process, the spin coater speed and the amount of photoresist can be adjusted to adjust the thickness of the photoresist layer.

[0055] In another example, before spin-coating the photoresist composition onto the surface of the wafer substrate, a step of filtering the photoresist composition with a filter membrane can be performed, wherein the filter membrane has a conventional small pore size.

[0056] In step S2, the wafer substrate is dried to form a photoresist film on the surface of the wafer substrate.

[0057] Specifically, the wafer substrate is dried using a drying device, and a photoresist film is formed on the surface of the wafer substrate after drying. For example, the wafer substrate is placed in a drying device with a base temperature of 90°C to 110°C for drying, and the drying time is set to 3 to 7 minutes, thereby removing moisture and some solvent from the photoresist film.

[0058] In step S3, the photoresist film is exposed and then baked.

[0059] Specifically, the obtained photoresist film is exposed to radiation using an exposure system. The exposure system can be a 254nm ultraviolet low-pressure mercury lamp exposure system, a 365nm ultraviolet high-pressure mercury lamp exposure system, a deep ultraviolet lithography system, an extreme ultraviolet lithography system, or an electron beam lithography system. Preferably, in this embodiment, the exposure system is an extreme ultraviolet lithography system. The photoresist layer after exposure is baked to cause the crosslinking agent in the exposed area of ​​the photoresist layer to undergo a crosslinking reaction. Specifically, the first crosslinking agent 131 is a low molecular weight crosslinking agent with short molecular chains, low viscosity, and a high diffusion coefficient, while the second crosslinking agent 132 is a high molecular weight crosslinking agent with a large molecular structure and a low diffusion coefficient. As a result, the first crosslinking agent 131 is more concentrated on the top layer of the photoresist, and the metal oxide nanoclusters and the first crosslinking agent 131 undergo a crosslinking reaction on the top layer of the photoresist to form a high crosslinking density region 141. Meanwhile, the second crosslinking agent 132 is more concentrated on the bottom layer of the photoresist, and the metal oxide nanoclusters and the second crosslinking agent 132 undergo a crosslinking reaction on the bottom layer of the photoresist to form a low crosslinking density region 142.

[0060] In step S4, the photoresist film is placed in a developer to develop in order to form a photolithographic pattern on the surface of the wafer substrate.

[0061] Specifically, a pattern mask is set on the top 151 of the photoresist film to block light, and then the exposed area is developed to form the desired photolithographic pattern. In this embodiment, the developer can be any one of isopropanol, toluene, o-xylene, m-xylene, p-xylene, cyclohexane, n-heptane, n-pentane, or butyl acetate.

[0062] As an example, for a positive development process, the low cross-linking density region 142 at the bottom 152 of the photoresist film reacts and dissolves faster, while the high cross-linking density region 141 at the top 151 of the photoresist film reacts and dissolves slower, effectively resisting lateral erosion by the developer and avoiding substrate defects.

[0063] As an example, for a negative development process 15, the cross-linking network of the high cross-linking density region 141 of the top 151 of the photoresist film can effectively prevent excessive penetration of the developer, while ensuring that the low cross-linking density region 142 of the bottom 152 of the photoresist film is completely dissolved, thereby avoiding photoresist residue 123 and T-top defects, and finally obtaining a high degree of verticality.

[0064] In summary, the photoresist composition with varying crosslinking density and its patterning method of the present invention, compared with the prior art, introduces a low-molecular-weight first crosslinking agent and a high-molecular-weight second crosslinking agent into the photoresist composition. This allows the photoresist composition to undergo a crosslinking reaction during the baking process after exposure to form the photolithographic pattern. Since the diffusion rate of the first crosslinking agent is greater than that of the second crosslinking agent, a gradient distribution of crosslinking density from top to bottom is achieved in the photoresist film. This ensures a balanced reaction rate during the developer penetration process in subsequent development, thereby significantly reducing the probability of various defects. Specifically, in the positive development process, the formation of base defects is effectively suppressed, ensuring the verticality of the photolithographic pattern sidewalls. In the negative development process, bottom residue and T-top defects are avoided, significantly improving pattern integrity and resolution. Furthermore, based on the high sensitivity and resolution advantages of metal oxide photoresists themselves, combined with the gradient change of crosslinking density in the photoresist composition, fine pattern processing at 16nm can be achieved. Therefore, the present invention effectively overcomes the various shortcomings of the prior art and has high industrial application value.

[0065] The above embodiments are merely illustrative of the principles and effects of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or alter the above embodiments without departing from the spirit and scope of the present invention. Therefore, all equivalent modifications or alterations made by those skilled in the art without departing from the spirit and technical concept disclosed in the present invention should still be covered by the claims of the present invention.

Claims

1. A photoresist composition with a crosslinking density gradient, characterized in that, include: Metal oxide nanoclusters, comprising a metal oxide core and an organic ligand coordinated with the metal oxide core, having the general molecular formula MxOyRmLn, wherein M is a metal element, L is a photosensitive anion or cation ligand, R is a polymerizable organic ligand, and O is an oxygen atom. The crosslinking agent includes a first crosslinking agent and a second crosslinking agent, wherein the first crosslinking agent is a low molecular weight crosslinking agent and the second crosslinking agent is a high molecular weight crosslinking agent; Photoinitiators and solvents.

2. The photoresist composition with varying crosslinking density according to claim 1, characterized in that: M is selected from any one of titanium, tin, zirconium, zinc, copper, iron, cobalt, nickel, silver, and hafnium.

3. The photoresist composition with varying crosslinking density according to claim 1, characterized in that: The low molecular weight crosslinking agent includes acrylic resin or epoxy resin with a molecular weight of less than 300 and possessing bifunctional groups.

4. The photoresist composition with varying crosslinking density according to claim 3, characterized in that: The difunctional acrylic resin includes at least one of ethylene glycol diacrylate, alkyl acrylate, hydroxyl-containing acrylate, polypropylene glycol acrylate, or polytetramethylene glycol acrylate.

5. The photoresist composition with varying crosslinking density according to claim 1, characterized in that: The high molecular weight crosslinking agent includes acrylic resin or epoxy resin with a molecular weight greater than 300 and possessing multiple functional groups.

6. The photoresist composition with varying crosslinking density according to claim 5, characterized in that: The multifunctional acrylic resin includes at least one of trimethylolpropane acrylate, pentaerythritol acrylate, alkoxylated glycerol acrylate, or dimeric pentaerythritol acrylate.

7. The photoresist composition with varying crosslinking density according to claim 1, characterized in that: The first crosslinking agent accounts for 20% to 50% of the crosslinking agent, and the second crosslinking agent accounts for 50% to 80% of the crosslinking agent.

8. The photoresist composition with varying crosslinking density according to claim 1, characterized in that: The solvent is one or more selected from ethyl lactate, butyl acetate, propylene glycol methyl ether acetate, methanol, ethanol, and propanol.

9. The photoresist composition with varying crosslinking density according to any one of claims 1 to 8, characterized in that: The diffusion rate of the first crosslinking agent is greater than that of the second crosslinking agent.

10. A method for forming a photolithographic pattern, characterized in that, include: The photoresist composition of any one of claims 1 to 9 is coated on the surface of a wafer substrate; The wafer substrate is dried to form a photoresist film on the surface of the wafer substrate; The photoresist film is exposed and then baked after the exposure. The photoresist film is placed in a developer to develop in order to form a photolithographic pattern on the surface of the wafer substrate.

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