A photoresist and its use

Abstract

The application discloses a photoresist and application thereof. The photoresist comprises the following raw materials in parts by mass: 10 parts of resin, 0.1-1 parts of photoacid and 0.1-1 parts of phenyltrimethoxysilane. The resin is an A-B type block copolymer, wherein the A block is a poly-p-hydroxystyrene segment, and the B block is a copolymer segment of tert-butyl methacrylate and methacrylic acid. The photoresist can be used to prepare a photoresist layer which is ultra-thin and has ultra-high uniformity, and meets the requirement of fine pattern processing. The application also provides the application of the photoresist.

Description

Technical Field

[0001] This invention relates to the field of photoresist technology, specifically to a photoresist and its applications. Background Technology

[0002] Electron beam lithography is one of the highest-resolution photolithography technologies currently available. Electron beams have extremely short equivalent wavelengths (typically around 0.007–0.01 nm), making it a crucial technique for fabricating nanostructures such as nanowires, quantum dots, and superconducting devices, as well as high-end photomasks with nanoscale precision patterns. As the feature sizes of semiconductors and nanodevices continue to shrink to 10 nm or even smaller, the requirements for photoresist resolution are constantly increasing. During electron beam lithography, electron scattering in the photoresist induces the proximity effect, thereby reducing pattern precision. Using ultra-thin photoresist layers (e.g., thickness < 30 nm) is considered one of the effective ways to improve resolution and reduce the proximity effect.

[0003] Currently, polymethyl methacrylate (PMMA) is one of the most widely used photoresist materials in electron beam lithography. It has high resolution, but it also has problems such as low sensitivity, high required exposure dose, long exposure time, and difficulty in achieving stable ultrathin coatings. The existing thin-layer photoresists have the following main problems in practical applications: (1) Insufficient adhesion: The adhesion between ultrathin photoresists and silicon wafers is weak, and they are prone to falling off or generating defects during development or subsequent processing; (2) Limited etching resistance: When ultrathin photoresists are used as etching masks, their thickness is insufficient to withstand dry or wet etching processes, and they are easily consumed quickly during etching, leading to pattern transfer failure; (3) Difficulty in controlling film uniformity: At the ultrathin scale, traditional spin coating processes are difficult to obtain photoresist film layers with uniform thickness and fewer defects, affecting patterning quality and repeatability.

[0004] Therefore, there is an urgent need to develop photoresists that can meet the requirements of ultra-thin film formation, while also possessing high resolution, high sensitivity, good adhesion, and sufficient etching resistance. Summary of the Invention

[0005] This invention proposes a photoresist that can be used to prepare ultra-thin photoresist layers with ultra-high uniformity, thereby better meeting the needs of fine pattern processing.

[0006] The present invention also proposes the application of the photoresist.

[0007] The present invention also proposes a method for preparing nanopatterns using the aforementioned photoresist.

[0008] The first aspect of the present invention relates to a photoresist comprising the following raw materials in parts by weight: 10 parts resin, 0.1-1 parts photoacid, and 0.1-1 parts phenyltrimethoxysilane; wherein the resin is an AB-type block copolymer, wherein the A block is a poly(p-hydroxystyrene) segment (PHOST), and the B block is a copolymer segment of tert-butyl methacrylate and methacrylic acid.

[0009] The photoresist according to the first aspect of the present invention has at least the following beneficial effects: The optimized design of the A and B block types in the block copolymer achieves excellent film uniformity in ultrathin photoresist layers. This block copolymer structure can achieve a highly ordered arrangement through molecular self-assembly during film formation, thus obtaining excellent film uniformity. At an ultrathin thickness of approximately 10 nm, thickness fluctuations can be controlled within ±0.7 nm. Research results show that, compared with random A and B copolymers with the same monomer composition, or block copolymers where the B block does not contain methacrylic acid, the block structure of the resin used in this invention has significant advantages in film uniformity.

[0010] Phenylacetyltrimethoxysilane (PTMS) was used as a adhesion promoter. The phenyl groups at the ends of PTMS molecules can generate significant π–π stacking interactions and hydrophobic compatibility effects with the benzene ring structure of the poly(p-hydroxystyrene) segments in the A-block of the resin. This promotes a highly ordered directional arrangement of the A-block at the substrate interface, forming a flexible interface layer with low defect density and effective relaxation of internal stress between the photoresist layer and the substrate. This interface layer not only significantly improves the adhesion of the photoresist to the substrate but also effectively ensures the structural stability of the ultrathin photoresist film during spin coating, baking, and development. Therefore, after spin coating, this photoresist can produce an ultrathin continuous film with a surface roughness (Ra) of less than 0.3 nm and a thickness non-uniformity (1σ) within ±0.7 nm, ensuring high precision and low defects in subsequent patterning from the source. At the same time, the B-block provides electron beam sensitive sites, ensuring high sensitivity. In contrast, silane coupling agents containing other common reactive or polar functional groups (such as KH-570 and APTES) can improve adhesion to some extent, but they are difficult to reduce film defect density and improve the uniformity of adhesive layer thickness at the same time.

[0011] Photoacids can generate acid sources under electron beam irradiation, causing the exposed areas to dissolve during the development process, thereby forming a predetermined nanoscale pattern structure.

[0012] According to some embodiments of the present invention, the B block is a random copolymer segment of tert-butyl methacrylate and methacrylic acid, or it can be a block copolymer structure, and the present invention does not limit it in this regard.

[0013] According to some embodiments of the present invention, the molar percentage of methacrylic acid units in the B block is 5% to 15%, for example, 5%, 8%, 10%, 12% or 15%.

[0014] According to some embodiments of the present invention, the A-block in the resin has a mass percentage of 20% to 40%, which can further improve the thickness uniformity of the photoresist layer. For example, the mass percentage of the A-block in the resin is 20%, 25%, 30%, 35%, or 40%.

[0015] According to some embodiments of the present invention, the number-average molecular weight of the resin is 25,000 g / mol to 35,000 g / mol, which can reduce the viscosity of the system, decrease the viscous resistance inside the adhesive during spin coating, and make the adhesive easier to flow and spread after the shear force stops, thus improving the uniformity of the coating film. For example, the number-average molecular weight of the resin is 25,000 g / mol, 28,000 g / mol, 30,000 g / mol, 32,000 g / mol, or 35,000 g / mol.

[0016] According to some embodiments of the present invention, the dispersity of the resin is ≤1.2, for example, 1.05~1.2 or 1.1~1.2. Herein, dispersity refers to the ratio of the number-average molecular weight to the weight-average molecular weight of the resin.

[0017] According to some embodiments of the present invention, the resin is prepared by reversible addition-fragmentation chain transfer polymerization (RAFT polymerization). Specifically, it can be prepared using techniques known in the art, for example, using 2-cyano-2-propyldodecyl trithiocarbonate as the RAFT agent and p-acetoxystyrene as the monomer, polymerizing in the presence of an initiator, followed by hydrolysis to obtain a poly(p-hydroxystyrene) structure with RAFT groups at the ends; specific reaction conditions (such as reaction temperature, feed ratio, etc.) are not limited.

[0018] According to some embodiments of the present invention, the photoacid is an onium salt compound. Specifically, the photoacid generator is selected from at least one of triarylthioonium salts, diaryliodonium salts, and their derivatives, wherein the derivatives include compounds in which the aromatic ring is substituted by an alkyl, alkoxy, or halogen group, and the anion can be selected from PF6. - SbF6 - BF6 - or CF3SO3 - At least one of them.

[0019] According to some embodiments of the present invention, the photoresist comprises the following raw materials in parts by weight: 10 parts resin, 0.1-0.5 parts photoacid, and 0.2-1 parts phenyltrimethoxysilane. Further, the raw materials comprise: 10 parts resin, 0.1-0.3 parts photoacid, and 0.2-0.8 parts phenyltrimethoxysilane.

[0020] According to some embodiments of the present invention, the raw materials for preparation further include organic solvents.

[0021] According to some embodiments of the present invention, the organic solvent is selected from at least one of ester and ketone solvents.

[0022] According to some embodiments of the present invention, the organic solvent is selected from at least one of propylene glycol methyl ether acetate, ethyl lactate, and cyclohexanone.

[0023] According to some embodiments of the present invention, the organic solvent in the raw materials is 85% to 98% by mass, for example, 85%, 90%, 95% or 98%.

[0024] The second aspect of the present invention relates to the application of the photoresist in the fabrication of photomasks, semiconductor devices or nano-optoelectronic devices.

[0025] A third aspect of the present invention relates to a method for fabricating nanopatterns using the photoresist, comprising the following steps: The photoresist is applied to the substrate by spin coating, cured, and then exposed to electron beam. After development, nano-patterns are formed in the resulting photoresist layer.

[0026] Furthermore, when preparing the photomask, the substrate can be a chromium-plated quartz glass substrate. After developing and forming the photoresist pattern, the photoresist pattern is used as an etching mask to etch the exposed chromium layer, thereby obtaining the photomask. The etching can be dry etching, and the etching gas can be a Cl2-based gas, such as Cl2 or a BCl3 / Cl2 mixture.

[0027] According to some embodiments of the present invention, the thickness of the photoresist layer is <30nm, and more specifically <15nm.

[0028] According to some embodiments of the present invention, the surface roughness Ra of the photoresist layer is ≤0.3 nm.

[0029] According to some embodiments of the present invention, when the photoresist layer has a film thickness of 10~11nm, the film thickness deviation is ≤0.7nm.

[0030] According to some embodiments of the present invention, the energy of the electron beam exposure is 20~50 μC / cm. 2 .

[0031] According to some embodiments of the present invention, the developing process uses an aqueous solution of tetramethylammonium hydroxide as the developing solution.

[0032] The present invention does not limit the curing temperature and curing time, which can be selected according to the type of solvent used and the film-forming characteristics. For example, it can be cured at 90~140℃ for 5~30min.

[0033] In this article, all numerical ranges include endpoint values ​​and cover any subranges within that range, such as ranges obtained by arbitrarily combining the specifically listed numerical values ​​or endpoint values.

[0034] Unless otherwise specified, all solutions mentioned in this article refer to aqueous solutions. Attached Figure Description

[0035] Figure 1 The images shown are AFM images of the surface morphology of the photoresist layers after curing in Examples 1, 4, and 5. Figure 1 (a)~ Figure 1 (c) Corresponding to Example 1, Comparative Example 3 and Comparative Example 2 respectively.

[0036] Figure 2 This is a schematic diagram illustrating the mechanism of action of different coupling agents in the photoresist system in Example 1, Comparative Example 4, and Comparative Example 5. Detailed Implementation

[0037] The embodiments of the present invention are described in detail below. These embodiments are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0038] Unless otherwise specified, all raw materials or equipment mentioned are commercially available and readily available.

[0039] Example 1 A photoresist, prepared from the following raw materials: Resin 2.0%, photoacid 0.02%, PTMS 0.10%, solvent 97.88%.

[0040] The photoacid is triphenylthionium trifluoromethanesulfonate, and the solvent is propylene glycol methyl ether acetate (PGMEA).

[0041] The preparation method of photoresist is as follows: dissolve resin and photoacid in solvent, stir and filter thoroughly, then add phenyltrimethoxysilane and mix evenly.

[0042] The resin is prepared as follows: 1. Synthesis of PHOST macromolecular chain transfer agent (PHOST-Macro-CTA): In a dry Schlenk flask, RAFT reagent 2-cyano-2-propyldodecyl trithiocarbonate (0.366 g, 1.0 mmol), monomer p-acetoxystyrene (16.0 g, 100 mmol), and initiator AIBN (3.28 mg, 0.02 mmol) were added and dissolved in 30 mL of anhydrous 1,4-dioxane. After three cycles of liquid nitrogen freezing-vacuuming-thawing to remove oxygen, the reaction was carried out in an oil bath at 70°C for 6 hours. The reaction solution precipitated in ice-cold diethyl ether to give a white solid. The solid was dissolved in tetrahydrofuran (THF), and excess 1M potassium hydroxide methanol solution was added. The mixture was hydrolyzed at 50°C for 12 hours. After the reaction was complete, the product was precipitated in a dilute hydrochloric acid aqueous solution (concentration 0.1M), filtered, and vacuum dried to obtain poly(p-hydroxystyrene) with RAFT-terminated groups (denoted as PHOST-Macro-CTA, yield: 4.62 g). GPC analysis (THF as mobile phase, polystyrene standard, the same below) showed: Mn = 10500 g / mol, dispersity... =1.12.

[0043] 2. Synthesis of the block copolymer: PHOST-Macro-CTA (4.62 g, 0.44 mmol), tert-butyl methacrylate (tBMA, 12.8 g, 90 mmol), methacrylic acid (MAA, 0.86 g, 10 mmol), and AIBN (0.13 mg, 0.8 μmol) were dissolved in 40 mL of anhydrous 1,4-dioxane. After deoxygenation, the mixture was reacted at 70°C for 8 hours. The reaction solution was precipitated twice in a hexane / isopropanol (9:1 v / v) mixture to obtain a white fibrous solid, which was vacuum dried to constant weight. This was the target block copolymer PHOST-bP (tBMA-co-10%MAA), with a yield of 17.3 g. GPC analysis showed Mn = 31200 g / mol and dispersity... =1.18.

[0044] Using nuclear magnetic resonance hydrogen spectroscopy (NMR) 1 ¹H NMR analysis, by integrating the characteristic proton signals, including the benzene ring hydrogen, tert-butyl proton, and MAA carboxyl proton signals of the PHOST block, calculated that the mass fraction of the PHOST block in the block copolymer is approximately 26.7%, and the molar percentage of methacrylic acid (MAA) units in the B block is approximately 10%.

[0045] Differential scanning calorimetry (DSC) analysis showed that the copolymer has two distinct and separate glass transition temperatures (Tg), with the PHOST block around 115℃ and the P(tBMA-co-MAA) block around 105℃. This confirmed that the polymer has a clear microphase separation structure, indicating that it is a block copolymer rather than a random copolymer.

[0046] Comparative Example 1 Compared with Example 1, the difference is that the MAA monomer in step 2 is replaced with an equimolar amount of tBMA monomer, that is, the total amount of tBMA monomer added is 100 mmol, and the other steps are the same as in Example 1. GPC determination shows: Mn = 31000 g / mol, D = 1.20.

[0047] Comparative Example 2 Compared with Example 1, the difference is that phenyltrimethoxysilane is replaced with an equal mass of KH-570, while the rest remains the same.

[0048] Comparative Example 3 Compared with Example 1, the difference is that phenyltrimethoxysilane is replaced with an equal mass of APTES (KH-550), while the rest remains the same.

[0049] Comparative Example 4 Compared with Example 1, the difference is that phenyltrimethoxysilane is replaced with an equal mass of solvent PGMEA, while the rest remains the same.

[0050] Test case A 6025 photomask substrate (quartz substrate) was used as the substrate, and photoresist was applied and verified on a rotary coater. The maximum rotation speed during the coating process was 1500~3500 rpm, and the rotation time at the maximum speed was 0.5~1.5 s. After coating, baking was performed at a temperature of 90~120℃ for 5 min~20 min.

[0051] Patterning: The cured photoresist layer is sequentially exposed, developed, and etched, with the electron beam exposure energy being 20~50 μC / cm. 2 A 1.83% tetramethylammonium hydroxide aqueous solution was used, with a development time of 40-60 seconds. Dry etching was used, with chlorine gas as the etching gas.

[0052] The surface roughness and film thickness uniformity of the cured photoresist layer were tested using atomic force microscopy (AFM). Figure 1 The images shown are AFM images of the surface morphology of the photoresist layers after curing in Examples 1, 2, and 3. Figure 1 (a)~ Figure 1 (c) Corresponding to Example 1, Comparative Example 3, and Comparative Example 2, respectively. Figure 1 (a) As can be seen, the surface of the photoresist layer using PTMS as a adhesion promoter is extremely smooth and uniform, with a single overall color distribution, and no obvious undulations or defects were observed. Figure 1 (c) As can be seen, the surface of the photoresist layer using KH-570 exhibits nanoscale wavy undulations; the overall film layer is continuous, but its flatness is significantly reduced. Figure 1 (b) As can be seen, the surface of the photoresist layer using APTES exhibits obvious aggregate protrusions and depressions, with a significantly increased surface roughness, presenting an uneven "hilly" morphology. This demonstrates that the surface morphology of the photoresist layer has a significant impact on film uniformity, and consequently affects the accuracy of subsequent photolithography patterns.

[0053] The photoresist layer characteristics of Example 1 and Comparative Example 1 are shown in Table 1.

[0054] Table 1

[0055] In Table 1, the thickness uniformity is calculated as follows: A PR adhesive thickness meter is used to measure the thickness at 121 points on the adhesive layer, and the standard deviation (1σ) of all measurements is calculated. Adhesive film condition: AFM, image scanning range is 5μm×5μm, and surface roughness Ra is the average value of measurements taken at 5 different locations on the adhesive layer surface.

[0056] As can be seen from Table 1, the block structure of the resin in the embodiments of the present invention can achieve excellent film uniformity (film thickness deviation ±0.7nm), which is significantly better than that of Comparative Example 1 (B block without MAA).

[0057] The photoresist layer characteristics of Examples 1 and Comparative Examples 2-4 are shown in Table 2.

[0058] Table 2

[0059] In Table 2, Ra represents the average roughness, and Rq represents the root mean square roughness. Five locations were tested for each sample.

[0060] Table 2 shows that PTMS is significantly better than other silane coupling agents in reducing defect density and improving adhesive thickness uniformity. This may be due to the π-π stacking effect between its phenyl group and the PHOST block benzene ring in the resin, which helps to achieve ultrathin, high-quality film formation.

[0061] As shown in Table 2, phenyltrimethoxysilane (PTMS) containing hydrophobic phenyl groups achieves excellent film formation. In contrast, while silane coupling agents containing other common reactive or polar functional groups (such as KH-570 and APTES) can improve the adhesion of photoresist to the substrate to some extent, they cannot effectively reduce the density of film defects or significantly improve the uniformity of the resist layer thickness.

[0062] Figure 2 This is a schematic diagram illustrating the mechanism of action of different coupling agents in a photoresist system, where... Figure 2 (a)~(c) correspond to Example 1, Comparative Example 2, and Comparative Example 3, respectively. The light-colored layer at the bottom of the figures is the substrate, and a photoresist layer is coated on the upper surface of this light-colored layer. Figure 2 As shown in (a), in Example 1, the phenyl groups at the ends of the PTMS molecules can interact with the benzene rings of the PHOST blocks in the resin through π–π stacking, causing the aromatic structures to be closely arranged along the interface, forming an ordered "aromatic stack" interface phase. This interface phase acts like a "molecular template," guiding the resin segments to spread out regularly on it, thereby achieving continuous and flat ultrathin film formation.

[0063] like Figure 2 As shown in (b), in Comparative Example 2, the KH-570 molecule ends with an aliphatic olefin segment, which has only a weak van der Waals interaction with the aromatic group of the PHOST block. The interface arrangement is disordered, the resin segment spreads and is oriented randomly, making it difficult to form a highly uniform film.

[0064] like Figure 2 As shown in (c), in Comparative Example 3, the polar amino groups at the ends of APTES molecules have a significant repulsive effect on the hydrophobic aromatic system, resulting in uneven distribution of APTES molecules at the substrate interface, forming discrete “island-like” structures, which interfere with the continuous film formation of the upper resin, leading to phase separation and film formation defects.

[0065] In summary, the photoresist of the present invention can achieve high-quality, low-defect coating of ultrathin films (<15nm), with a surface roughness Ra less than 0.30nm, Rq less than 0.5nm, film thickness deviation controlled within ±0.7nm, and defect density reduced to <0.5 defects / cm. 2 This ensures the accuracy of subsequent patterning from the source and is suitable for high-end electron beam exposure patterning processes.

[0066] The present invention has been described in detail above with reference to the embodiments. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A photoresist, characterized in that, The following raw materials are included in the preparation by weight: 10 parts resin, 0.1-1 parts photosensitive acid, and 0.1-1 parts phenyltrimethoxysilane; The resin is an AB-type block copolymer, wherein block A is a poly(p-hydroxystyrene) segment and block B is a copolymer segment of tert-butyl methacrylate and methacrylic acid.

2. The photoresist according to claim 1, characterized in that, The B block is a random copolymer segment of tert-butyl methacrylate and methacrylic acid; And / or, in the B block, the molar percentage of methacrylic acid units is 5% to 15%.

3. The photoresist according to claim 1, characterized in that, In the resin, the mass percentage of block A is 20% to 40%.

4. The photoresist according to claim 1, characterized in that, The number-average molecular weight of the resin is 25000 g / mol to 35000 g / mol; and / or, the dispersity of the resin is ≤1.

2.

5. The photoresist according to claim 1, characterized in that, The resin is prepared by reversible addition-fragmentation chain transfer polymerization.

6. The photoresist according to claim 1, characterized in that, The photoacid is an onium salt compound; And / or, the raw materials for preparation may also include organic solvents.

7. The photoresist according to claim 6, characterized in that, The organic solvent is selected from at least one of ester and ketone solvents; and / or, the organic solvent accounts for 85% to 98% of the mass of the raw materials used in the preparation.

8. The use of the photoresist according to any one of claims 1-7 in the preparation of photomasks, semiconductor devices or nano-optoelectronic devices.

9. A method for preparing nanopatterns using the photoresist according to any one of claims 1-7, characterized in that, Includes the following steps: The photoresist is applied to the substrate by spin coating, cured, and then exposed to electron beam. After development, nano-patterns are formed in the resulting photoresist layer.

10. The method according to claim 9, characterized in that, The thickness of the photoresist layer is <30nm; And / or, the surface roughness Ra of the photoresist layer is ≤0.3 nm; And / or, when the photoresist layer has a film thickness of 10~11nm, the film thickness deviation is ≤0.7nm; And / or, the energy of the electron beam exposure is 20~50 μC / cm. 2 .

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