A method for preparing a photoresist coating

Abstract

The application discloses a preparation method of a photoetching coating, which comprises the following steps: S1, mixing titanium white powder and cesium carbonate, calcining to obtain a solid; S2, acid dipping the solid, solid-liquid separation, adding the obtained solid phase into a tetramethylammonium hydroxide solution to stir, and peeling to obtain a titanium dioxide dispersion liquid; S3, adding a coupling agent into the titanium dioxide dispersion liquid to modify, solid-liquid separation, and ball milling to obtain modified titanium dioxide; S4, dissolving a hydroxyl-terminated hyperbranched polyester in a solvent, adding the modified titanium dioxide, ultrasonic dispersion, adding a vinyl-terminated compound to mix to obtain a mixed liquid; and S5, coating the mixed liquid on a substrate, and heating and curing to obtain the photoetching coating. The prepared photoetching coating has a high refractive index, is easy to remove through developing, and can be used for preparing a photomask plate.

Description

Technical Field

[0001] This invention relates to the field of photomask materials technology, and more specifically to a method for preparing a photolithographic coating. Background Technology

[0002] A photomask, also known as a photomask, typically uses quartz glass with low thermal expansion and high light transmittance as the substrate. A pattern (circuit pattern template) is formed on the substrate surface using metallic chromium (Cr) as a light-shielding layer. In photolithography, processes such as exposure, development, and etching are used to proportionally reduce the pattern on the photomask and transfer it onto a silicon substrate to form the circuit pattern. With the miniaturization trend in the microelectronics industry, the resolution requirements for integrated circuits are increasing. To reduce the impact of manufacturing defects and errors on the photomask on chip quality, it is necessary to improve the quality of the photomask to meet the high-precision processing requirements of integrated circuits.

[0003] The basic steps for forming patterns on a photomask are similar to those for silicon wafers, requiring processes such as exposure, development, and etching. Due to optical reflection, reflected light interferes with incident light, creating standing wave effects and multiple exposures within the photoresist. This leads to deviations in pattern dimensions, such as contour distortion, decreased contrast, blurred edges, and rounded corners. Anti-reflective coatings can reduce light interference in the photoresist, minimizing processing errors.

[0004] Existing antireflective coatings include two types: organic and inorganic. Among them, the molding and removal processes of inorganic antireflective coatings are complex. Organic antireflective coatings mainly utilize the dyeing groups in polymers to absorb ultraviolet light to reduce light reflection. Most of them require complex synthesis processes to introduce light-absorbing groups, and there is also the problem that they are difficult to remove completely through the development process. Summary of the Invention

[0005] This invention aims to at least solve one of the technical problems existing in the prior art. To this end, this invention proposes a method for preparing a photolithographic coating, which produces a photolithographic coating with a high refractive index and is easily removed by development.

[0006] The present invention also provides a photolithographic coating prepared by the above-described preparation method.

[0007] The present invention also provides the above-described preparation method or the application of the above-described photolithographic coating in the preparation of photomasks.

[0008] Specifically, the first aspect of the present invention relates to a method for preparing a photolithographic coating, comprising the following steps:

[0009] S1. Titanium dioxide and cesium carbonate are mixed and calcined to obtain a solid.

[0010] S2. The solid is acid-leached, and the solid and liquid are separated. The resulting solid phase is added to a tetramethylammonium hydroxide solution and stirred. The solid phase is then peeled off to obtain a titanium dioxide dispersion.

[0011] S3. Add a coupling agent to the titanium dioxide dispersion for modification, perform solid-liquid separation, and ball milling to obtain modified titanium dioxide;

[0012] S4. Dissolve the hydroxyl-terminated hyperbranched polyester in a solvent, add the modified titanium dioxide, disperse ultrasonically, add the vinyl-terminated compound and mix to obtain a mixture;

[0013] S5. The mixture is coated onto the substrate and heated to cure, thus obtaining a photolithographic coating.

[0014] The method for preparing a photolithographic coating according to the first aspect of the present invention has at least the following beneficial effects:

[0015] Titanium dioxide and cesium carbonate are calcined to form a layered cesium titanate structure. Acid leaching causes proton exchange, displacing the cesium. Exfoliation with tetramethylammonium hydroxide yields sheet-like titanium dioxide. After surface modification with a coupling agent, the dispersibility of the sheet-like titanium dioxide is improved. Further ball milling refines it into even smaller two-dimensional sheet structures. These two-dimensional sheet structures can form multi-layered surface structures, causing refraction, scattering, and interference of incident light between different layers, reducing incident light reflection and improving photolithography precision.

[0016] Hydrogen bonds can be formed between the hydroxyl-terminated hyperbranched polyester and the titanium dioxide sheets, which not only improves the dispersibility of titanium dioxide but also facilitates the formation of an interlaced structure, providing more space for the refraction of incident light and further suppressing the reflection of incident light.

[0017] The terminal hydroxyl groups of hyperbranched polyester react with terminal vinyl compounds to form a large-scale, dense network structure. Simultaneously, titanium dioxide enhances the coating's density and barrier properties, improving corrosion resistance and making the coating less soluble in photoresist solvents or alkaline developers, thus meeting the requirements of subsequent photolithography processes. In the presence of a photoacid generator (added to the photoresist coating or located on top of it), acid is generated in the exposed area (when the photoacid generator is added to the photoresist, the acid generated after exposure diffuses to the photoresist coating; when the photoacid generator is added to the photoresist coating, ultraviolet light can penetrate the nano-titanium dioxide layer to generate acid), causing the network structure to depolymerize. Furthermore, the highly branched molecular structure of hyperbranched polyester provides good hydrodynamic volume, making it easier to remove with alkaline developers.

[0018] According to some embodiments of the present invention, in step S1, the titanium dioxide is rutile.

[0019] According to some embodiments of the present invention, in step S1, the molar ratio of titanium dioxide to cesium carbonate is 4.5-5:1.

[0020] According to some embodiments of the present invention, in step S1, the calcination temperature is 800-830°C and the calcination time is 10-15 hours.

[0021] According to some embodiments of the present invention, in step S2, the acid leaching uses hydrochloric acid with a concentration of 1-2M.

[0022] According to some embodiments of the present invention, in step S2, the acid leaching time is 80-100 hours.

[0023] According to some embodiments of the present invention, in step S2, the solid-liquid ratio of the acid leaching is 0.8-1.5 g / 100 mL.

[0024] According to some embodiments of the present invention, in step S2, the acid leaching is carried out under stirring. There are no particular requirements for the stirring rate; the main purpose is to create disturbance to facilitate sufficient contact between the acid and the solid.

[0025] According to some embodiments of the present invention, in step S2, the solid-liquid separation is performed by filtration.

[0026] According to some embodiments of the present invention, step S2 further includes washing and drying the product after solid-liquid separation.

[0027] According to some embodiments of the present invention, in step S2, the concentration of the tetramethylammonium hydroxide solution is 0.1-0.15M.

[0028] According to some embodiments of the present invention, in step S2, the mass-to-volume ratio of the solid phase to the tetramethylammonium hydroxide solution is 1-2 g / 100 mL.

[0029] According to some embodiments of the present invention, in step S2, the stirring time is 70-80 hours. There are no particular requirements regarding the stirring rate.

[0030] The concentration, dosage, and processing time of tetramethylammonium hydroxide were controlled to efficiently peel off sheet-like titanium dioxide.

[0031] According to some embodiments of the present invention, in step S2, the mixture is allowed to stand after stirring to remove the lower precipitate.

[0032] According to some embodiments of the present invention, in step S3, the coupling agent is trimethoxy(3-methoxypropyl)silane, where the methoxypropyl group forms a hydrogen bond structure with the terminal hydroxyl polyester, which is beneficial for the dispersion of titanium dioxide.

[0033] According to some embodiments of the present invention, in step S3, the mass-to-volume ratio of the coupling agent to the titanium dioxide dispersion is 0.05-0.3 g / 100 mL.

[0034] According to some embodiments of the present invention, in step S3, the modification temperature is 40-50°C and the modification time is 5-10 hours.

[0035] According to some embodiments of the present invention, in step S2, the solid-liquid separation is performed by centrifugation, with a centrifugation speed of 7000-8000 rpm and a centrifugation time of 8-10 min.

[0036] According to some embodiments of the present invention, in step S3, the solid-liquid separation is followed by washing.

[0037] According to some embodiments of the present invention, in step S3, the ball milling uses a ball milling bead gradation of the following diameters: 8-10 mm and 4-5 mm, with a gradation ratio of 1:2-3. This gradation effectively refines the flake diameter and reduces excessive damage to the flake structure.

[0038] According to some embodiments of the present invention, in step S3, the ball milling speed is 80-120 rpm, the ball milling time is 2-5 h, and the ball-to-material ratio is 4-8:1. In this text, the ball-to-material ratio refers to the mass ratio of the grinding balls to the solid material to be ground.

[0039] According to some embodiments of the present invention, in step S3, the ball milling medium is ethylene glycol, and the mass ratio of the medium to the solid material to be milled is 1-2:1.

[0040] According to some embodiments of the present invention, in step S3, the ball milling is followed by drying.

[0041] According to some embodiments of the present invention, in step S4, the terminal hydroxyl hyperbranched polyester has a functionality of 5-7, a hydroxyl value of 500-700 mgKOH / g, and a molecular weight of 500-600 g / mol.

[0042] According to some embodiments of the present invention, in step S4, the terminal vinyl compound is triethylene glycol divinyl ether or diethylene glycol divinyl ether.

[0043] According to some embodiments of the present invention, in step S4, the total mass ratio of the hydroxyl-terminated hyperbranched polyester and the vinyl-terminated compound to the modified titanium dioxide is 1.8-2:1.

[0044] According to some embodiments of the present invention, in step S4, the molar ratio of the hydroxyl-terminated hyperbranched polyester to the vinyl-terminated compound is 1:8-12. This ensures a suitable excess of the vinyl-terminated compound, which facilitates the crosslinking reaction and guarantees a certain degree of crosslinking.

[0045] According to some embodiments of the present invention, in step S4, the solvent is an alcohol ether solvent, for example, selected from at least one of propylene glycol monomethyl ether, diethylene glycol monomethyl ether, diethylene glycol monoethyl ether, dipropylene glycol dimethyl ether or diethylene glycol dimethyl ether.

[0046] According to some embodiments of the present invention, in step S4, the mass ratio of the terminal hydroxyl hyperbranched polyester to the solvent is 0.2-0.5:98-100.

[0047] According to some embodiments of the present invention, step S4 further includes adding at least one of a photoacid generator or a photoquencher to the mixture. When a photoacid generator or a photoquencher is added to the photoresist layer, the above-mentioned components may be added in small amounts or not at all to the mixture.

[0048] The photoacid generator and quencher can be selected from types known in the art. For example, the photoacid generator can be at least one of bis(4-tert-butylphenyl)iodonium perfluorobutane sulfonate (CAS: 194999-85-4), perfluorobutylsulfonate triphenylsulfonate (CAS: 144317-44-2), triphenylsulfonate trifluoromethane sulfonate (CAS: 66003-78-9), and N-hydroxynaphthalimide trifluoromethane sulfonic acid (CAS: 85342-62-7).

[0049] The amount of photoacid generator can be 20%-30% of the total mass of the terminal hydroxyl hyperbranched polyester and the terminal vinyl compound.

[0050] Quenching agents are generally amino-containing compounds, specifically triethanolamine and / or trioctylamine, used to inhibit acid diffusion and reduce dimensional errors in unexposed areas.

[0051] The mass of the quenching agent can be 3-5% of the mass of the photoacid generator.

[0052] According to some embodiments of the present invention, in step S4, the ultrasonic dispersion time is 0.5-1h.

[0053] According to some embodiments of the present invention, in step S5, the heating temperature is 200-210°C and the heating time is 90-150 seconds.

[0054] According to some embodiments of the present invention, in step S5, the coating method is spin coating.

[0055] According to some embodiments of the present invention, in step S5, the thickness of the photolithographic coating is 100-150 nm.

[0056] According to some embodiments of the present invention, in step S5, the substrate is a quartz glass plate or a Cr-plated quartz glass plate. When a quartz glass plate is used, photoresist can be coated on the outside of the photolithographic coating, and after photolithography and development, Cr is deposited in the exposed area. When a Cr-plated quartz glass plate is used, photoresist can be coated on the outside of the photolithographic coating, and after photolithography and development, the exposed Cr is removed, thereby forming a metal pattern. The above-described fabrication process of the photomask is a mature technology in the art and is not described in detail.

[0057] The second aspect of the present invention relates to a photolithographic coating prepared using the aforementioned preparation method.

[0058] The photolithographic coating referred to has a high refractive index and is easy to remove through development, which can improve the precision and efficiency of photolithography.

[0059] According to some embodiments of the present invention, the thickness of the photolithographic coating is 100-150 nm.

[0060] The third aspect of the present invention relates to the application of the aforementioned preparation method or photolithographic coating in the preparation of photomasks.

[0061] Given the advantages of the aforementioned preparation methods or photolithographic coatings, the processing accuracy of photomasks can be improved.

[0062] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. Detailed Implementation

[0063] The embodiments of the present invention are described in detail below. The embodiments described below are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0064] In the following examples, some of the raw materials are described below:

[0065] Hydroxyl-terminated hyperbranched polyester, Wuhan Hyperbranched Resin Technology Co., Ltd., grade H101, functionality 5-7, hydroxyl value 670mgKOH / g, molecular weight 500g / mol.

[0066] Triethylene glycol divinyl ether, CAS: 765-12-8.

[0067] Trimethoxy(3-methoxypropyl)silane, CAS: 33580-59-5.

[0068] Titanium dioxide, DuPont R-902.

[0069] Unless otherwise specified, all raw materials involved are commercially available standard products.

[0070] Example 1

[0071] A method for preparing a photolithographic coating, comprising the following steps:

[0072] 1. Titanium dioxide and cesium carbonate are ground at a molar ratio of 5:1 and then placed in a muffle furnace and calcined at 810℃ for 15 hours to obtain a solid.

[0073] 2. The obtained solid was placed in 1.2M hydrochloric acid for acid leaching, with a solid-liquid ratio of 1g / 100mL. The mixture was stirred for 100h, filtered, washed with deionized water, and dried. The solid was then added to 0.15M tetramethylammonium hydroxide solution, with a solid-liquid ratio of 1.5g / 100mL. The mixture was stirred for 80h. After the peeling was completed, the mixture was allowed to stand, and the upper liquid was taken to obtain a titanium dioxide dispersion.

[0074] 3. Trimethoxy(3-methoxypropyl)silane was added to the obtained titanium dioxide dispersion for modification. The mass-to-volume ratio of trimethoxy(3-methoxypropyl)silane to titanium dioxide dispersion was 0.25 g / 100 mL. The mixture was heated to 45 °C and stirred at a constant temperature for 10 h. After centrifugation at 7000 rpm for 10 min, the mixture was dried and then ball-milled (10 mm zirconium beads and 5 mm zirconium beads in a mass ratio of 1:2.5, ethylene glycol as the ball milling medium, a material-to-liquid ratio of 1:1.5, a ball-to-material ratio of 6:1, a ball milling speed of 100 rpm, and a ball milling time of 4 h). The mixture was then dried to obtain modified titanium dioxide.

[0075] 4. Hydroxyl-terminated hyperbranched polyester (H101) and diethylene glycol dimethyl ether were stirred and dissolved at a mass ratio of 0.3:100. Modified titanium dioxide was then added, and the mixture was ultrasonically dispersed for 0.5 h. Triethylene glycol divinyl ether (the molar ratio of hydroxyl-terminated hyperbranched polyester to triethylene glycol divinyl ether was 1:9) was added and mixed, wherein the mass ratio of the total mass of the hydroxyl-terminated hyperbranched polyester and the terminal vinyl compound to the mass of modified titanium dioxide was 2:1. Based on the total mass of the hydroxyl-terminated hyperbranched polyester and triethylene glycol divinyl ether, 20% of bis(4-tert-butylphenyl)iodonium perfluorobutane sulfonate was added, followed by trioctylamine (3% of the mass of bis(4-tert-butylphenyl)iodonium perfluorobutane sulfonate) and mixed to obtain a mixture.

[0076] 5. Spin-coat the obtained mixture onto a quartz glass plate and cure at 205℃ for 120s to obtain a photolithographic coating with a thickness of 130nm.

[0077] Example 2

[0078] A method for preparing a photolithographic coating, comprising the following steps:

[0079] 1. Titanium dioxide and cesium carbonate are ground at a molar ratio of 5:1 and then placed in a muffle furnace and calcined at 820°C for 15 hours to obtain a solid.

[0080] 2. The obtained solid was placed in 1.2M hydrochloric acid for acid leaching, with a solid-liquid ratio of 1.1g / 100mL. The mixture was stirred for 100h, filtered, washed with deionized water, and dried. The solid was then added to 0.12M tetramethylammonium hydroxide solution, with a solid-liquid ratio of 1g / 100mL. The mixture was stirred for 80h. After the peeling was completed, the mixture was allowed to stand, and the upper liquid was taken to obtain a titanium dioxide dispersion.

[0081] 3. Trimethoxy(3-methoxypropyl)silane was added to the obtained titanium dioxide dispersion for modification. The mass-to-volume ratio of trimethoxy(3-methoxypropyl)silane to titanium dioxide dispersion was 0.2 g / 100 mL. The mixture was heated to 50 °C and stirred at a constant temperature for 10 h. After centrifugation at 7000 rpm for 10 min, the mixture was dried and then ball-milled (10 mm zirconium beads and 5 mm zirconium beads in a mass ratio of 1:2.5, ethylene glycol as the ball milling medium, a material-to-liquid ratio of 1:2, a ball-to-material ratio of 5:1, a ball milling speed of 90 rpm, and a ball milling time of 5 h). The mixture was then dried to obtain modified titanium dioxide.

[0082] 4. Hydroxyl-terminated hyperbranched polyester (H101) and diethylene glycol dimethyl ether were stirred and dissolved at a mass ratio of 0.3:100. Modified titanium dioxide was then added, and the mixture was ultrasonically dispersed for 0.5 h. Triethylene glycol divinyl ether (the molar ratio of hydroxyl-terminated hyperbranched polyester to triethylene glycol divinyl ether was 1:10) was added and mixed, wherein the mass ratio of the total mass of the hydroxyl-terminated hyperbranched polyester and the vinyl compound to the mass of modified titanium dioxide was 1.8:1. Based on the total mass of the hydroxyl-terminated hyperbranched polyester and triethylene glycol divinyl ether, 20% of bis(4-tert-butylphenyl)iodonium perfluorobutane sulfonate was added, followed by trioctylamine (3% of the mass of bis(4-tert-butylphenyl)iodonium perfluorobutane sulfonate) and mixed to obtain a mixture.

[0083] 5. Spin-coat the obtained mixture onto a quartz glass plate and cure at 205℃ for 120s to obtain a photolithographic coating with a thickness of 120nm.

[0084] Comparative Example 1

[0085] Compared with Example 1, the difference is that no coupling agent was added in step 3 for modification, while the rest remained the same. Step 3 is as follows:

[0086] The titanium dioxide dispersion obtained in step 2 was stirred at 45°C for 10 h, centrifuged at 7000 rpm for 10 min, dried, and then ball-milled (10 mm zirconium beads and 5 mm zirconium beads in a mass ratio of 1:2.5, the ball milling medium was ethylene glycol, the material-to-liquid ratio was 1:1.5, the ball-to-material ratio was 6:1, the ball milling speed was 100 rpm, and the ball milling time was 4 h) to obtain modified titanium dioxide.

[0087] Test case

[0088] 1. The n-value was measured using an ellipsometer at a wavelength of 248 nm.

[0089] 2. Photolithography performance test: Expose to 365nm UV light for 80s, PEB: 100℃ / 100s. Develop with 2.5wt% tetramethylammonium hydroxide developer for 60s, rinse with deionized water, and dry. Measure the initial thickness d0 and the thickness after development and drying using an ellipsometry (measure at five different locations and take the average value), and calculate the thickness difference (d0-d1). Measure the film thickness in the developed area and record it as d2.

[0090] The test results are shown in Table 1.

[0091] Table 1

[0092]

[0093]

[0094] The results above show that the photolithographic coatings in Examples 1 and 2 have higher refractive indices, and the thickness loss in the unexposed areas after development is small. The coating in the exposed areas is thoroughly removed after development, which is beneficial for improving photolithographic accuracy. In Comparative Example 1, the titanium dioxide, without coupling agent modification, may be difficult to disperse fully, resulting in a significant decrease in refractive index.

[0095] In summary, the photolithographic coating of this embodiment does not require the use of polymers with dyeing groups, can obtain a high refractive index, and is thoroughly removed after development, which is beneficial to improving photolithographic accuracy. It can be used to prepare photomasks and improve processing accuracy.

Claims

1. A method for preparing a photolithographic coating, characterized in that: Includes the following steps: S1. Titanium dioxide and cesium carbonate are mixed and calcined to obtain a solid. S2. The solid is acid-leached, and the solid and liquid are separated. The resulting solid phase is added to a tetramethylammonium hydroxide solution and stirred. The solid phase is then peeled off to obtain a titanium dioxide dispersion. S3. Add a coupling agent to the titanium dioxide dispersion for modification, perform solid-liquid separation, and ball milling to obtain modified titanium dioxide; S4. Dissolve the hydroxyl-terminated hyperbranched polyester in a solvent, add the modified titanium dioxide, disperse ultrasonically, add the vinyl-terminated compound and mix to obtain a mixture; S5. The mixture is coated onto the substrate and heated to cure, thus obtaining a photolithographic coating.

2. The method for preparing the photolithographic coating according to claim 1, characterized in that: In step S1, the molar ratio of titanium dioxide to cesium carbonate is 4.5-5:1; and / or, the calcination temperature is 800-830℃ and the calcination time is 10-15h.

3. The method for preparing the photolithographic coating according to claim 1, characterized in that: In step S2, the acid leaching uses hydrochloric acid with a concentration of 1-2M; and / or, the acid leaching time is 80-100h; and / or, the solid-liquid ratio of the acid leaching is 0.8-1.5g / 100mL; and / or, the concentration of the tetramethylammonium hydroxide solution is 0.1-0.15M; and / or, the mass-volume ratio of the solid phase to the tetramethylammonium hydroxide solution is 1-2g / 100mL; and / or, the stirring time is 70-80h.

4. The method for preparing the photolithographic coating according to claim 1, characterized in that: In step S3, the coupling agent is trimethoxy(3-methoxypropyl)silane; and / or, the mass-to-volume ratio of the coupling agent to the titanium dioxide dispersion is 0.05-0.3 g / 100 mL; and / or, the modification temperature is 40-50 °C, and the modification time is 5-10 h; and / or, the ball milling uses ball milling beads of the following diameters: 8-10 mm, 4-5 mm, with a gradation ratio of 1:2-3; and / or, the ball milling speed is 80-120 rpm, the ball milling time is 2-5 h, and the ball-to-material ratio is 4-8:1; and / or, the ball milling medium is ethylene glycol, and the mass ratio of the ball milling medium to the solid material to be milled is 1-2:

1.

5. The method for preparing the photolithographic coating according to claim 1, characterized in that: In step S4, the hydroxyl-terminated hyperbranched polyester has a functionality of 5-7, a hydroxyl value of 500-700 mgKOH / g, and a molecular weight of 500-600 g / mol; and / or, the total mass ratio of the hydroxyl-terminated hyperbranched polyester and the vinyl-terminated compound to the modified titanium dioxide is 1.8-2:1; and / or, the vinyl-terminated compound is triethylene glycol divinyl ether or diethylene glycol divinyl ether; and / or, the molar ratio of the hydroxyl-terminated hyperbranched polyester to the vinyl-terminated compound is 1:8-12; and / or, the solvent is an alcohol ether solvent; and / or, the mass ratio of the hydroxyl-terminated hyperbranched polyester to the solvent is 0.2-0.5:98-100; and / or, the ultrasonic dispersion time is 0.5-1 h.

6. The method for preparing the photolithographic coating according to claim 1, characterized in that: Step S4 further includes adding at least one of a photoacid generator or a quencher to the mixture.

7. The method for preparing the photolithographic coating according to claim 1, characterized in that: In step S5, the heating temperature is 200-210℃ and the heating time is 90-150s; and / or, the coating method is spin coating.

8. A photolithographic coating, characterized in that: The photolithographic coating is prepared using the preparation method described in any one of claims 1-7.

9. The photolithographic coating according to claim 8, characterized in that: The thickness of the photolithographic coating is 100-150 nm.

10. The application of the photolithographic coating as described in any one of claims 8-9 in the preparation of a photomask.

Images