A method for improving adhesion and / or development speed of photoresist

Abstract

The present application belongs to the field of microelectronic processing technology, and more particularly relates to a method for improving the adhesion and / or development speed of photoresist. For the photoresist system whose polarity changes from small to large significantly before and after photolithography, the adhesion between the photoresist and the silicon wafer substrate is significantly improved, and the development time is greatly shortened by using an alcohol solvent as a developer without using an adhesion promoter, compared with the alkaline aqueous solution developer commonly used in the prior art.

Description

Technical Field

[0001] This invention belongs to the field of microelectronic processing technology, and more specifically, relates to a method for improving photoresist adhesion and / or development speed. Background Technology

[0002] Traditional photolithography processes mainly consist of three steps: photoresist coating, exposure, and development. First, photoresist is uniformly coated on the substrate surface. Then, the photolithography machine exposes the mask pattern area. Finally, development is used to transfer the mask pattern to the substrate.

[0003] Current photoresist systems generally suffer from poor adhesion between the photoresist and the silicon wafer during the development process, causing even unexposed areas to detach from the silicon substrate. To improve adhesion, some existing techniques pre-coat the silicon wafer with a layer of HMDS, transforming the hydrophilic wafer into a hydrophobic one, thus increasing adhesion between the photoresist and the wafer. Other methods introduce monomers containing polar groups into the photoresist resin to further enhance adhesion. However, these methods either require additional processing steps or introduce extra reagents that affect the photoresist's exposure reaction, increasing costs.

[0004] Another problem with current photoresist systems during the development process is the slow development speed. For example, when using an alkaline solution as the developer, it is generally necessary to first use the alkaline solution as the developer to clean for 30 seconds or more, and then use deionized water to clean for 30 seconds or more, which affects the efficiency of the photolithography process. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a method for improving photoresist adhesion and / or development speed. By using an alcohol-based substance as the developer for photoresist systems where the polarity changes significantly from small to large before and after photolithography, the technical problems of poor adhesion between photoresist and silicon wafers and slow development speed in existing technologies are solved.

[0006] To achieve the above objectives, the present invention provides a method for improving photoresist adhesion and / or development speed, comprising the following steps:

[0007] (1) Photoresist is coated on the surface of a substrate to obtain a photoresist film; the photoresist includes a polymer resin, a photoacid generator and a solvent, wherein the polymer resin is a non-polar polymer resin or a weakly polar polymer resin.

[0008] (2) The photoresist film is exposed and baked after exposure using an exposure system. The polarity of the polymer resin in the photoresist in the exposed area increases before and after exposure, resulting in a photoresist film after photolithography.

[0009] (3) An alcohol solvent is used as a developing solution to develop the photoresist film after photolithography, thereby realizing the transfer of the mask pattern.

[0010] Preferably, the polymer resin in step (1) is selected from one or more of 4-tert-butoxycarbonyloxystyrene homopolymer, 4-tert-butoxycarbonyloxystyrene copolymer, tert-butyl vinyl benzoate homopolymer, tert-butyl vinyl benzoate copolymer, tert-butyl acrylate homopolymer, tert-butyl acrylate copolymer, tert-butyl methacrylate homopolymer, and tert-butyl methacrylate copolymer.

[0011] Preferably, the photoacid generator in step (1) is a sulfonate photoacid generator and / or an onium salt photoacid generator.

[0012] Preferably, the solvent in step (1) is one or more of tetrahydrofuran, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, ethyl lactate, cyclohexanone, toluene, p-xylene, and acetone.

[0013] Preferably, in step (2), the photoresist film is baked at 70-100℃ for 0.5-1 min before exposure, and the exposure energy during exposure is 50-100 mJ / cm. 2 After exposure, bake at 80-120℃ for 50-200 seconds.

[0014] Preferably, the alcohol solvent in step (3) is a small molecule alcohol solvent that is liquid at room temperature, and more preferably one or more of ethanol, propanol, isopropanol, n-butanol, isobutanol, sec-butanol, tert-butanol and n-pentanol.

[0015] Preferably, the developing time of the developing process is 1-60s, more preferably 5-20s.

[0016] Preferably, in step (3), an alcohol solvent is used as the developing solution, and after development, the residual alcohol solvent is purged with nitrogen.

[0017] In summary, compared with the prior art, the above-described technical solutions conceived by this invention have the following advantages:

[0018] Beneficial effects:

[0019] (1) This invention proposes a method to solve the poor adhesion between photoresist and silicon substrate and the slow development speed in photoresist systems with increased polarity during exposure. Without using thickeners, alcohol solvents are used as developers, which significantly improves the adhesion between photoresist and silicon substrate compared to the alkaline aqueous solutions commonly used in the prior art, and also greatly shortens the development time.

[0020] (2) In this invention, alcohol solvents are used instead of commonly used alkaline aqueous solutions as the developing solution. After development, the volatile alcohols can be quickly removed by nitrogen purging, eliminating the need for fixing (residual developing solution is removed by washing with deionized water), thus shortening the process time and improving efficiency. Attached Figure Description

[0021] Figure 1 The image shown is a photograph of Example 1 after development using ethanol as the developing solution.

[0022] Figure 2 This is a metallographic microscope image of Example 1 after development using ethanol as the developing solution.

[0023] Figure 3 The photographs after development using an alkaline aqueous solution as the developer are shown in Comparative Example 1.

[0024] Figure 4 The image shown is a metallographic microscope image developed using an alkaline aqueous solution as the developing solution, which is a comparative example 1.

[0025] Figure 5 The image shown is a photograph of the product developed using isopropanol as the developer in Example 2.

[0026] Figure 6 This is a metallographic microscope image of Example 2 after development using isopropanol as the developing solution.

[0027] Figure 7 The image shown is from Example 3 after development using n-hexanol as the developer.

[0028] Figure 8 This is a metallographic microscope image of Example 3 after development using n-hexanol as the developing solution.

[0029] Figure 9 The photograph shown in Example 4 is a developed image of tert-butyl polyvinyl benzoate as the resin.

[0030] Figure 10 Example 4 uses tert-butyl polyvinyl benzoate as the resin, and the resulting metallographic microscope image is shown. Detailed Implementation

[0031] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0032] Photoresist, also known as photoresist, broadly refers to a mixture that, after being irradiated or exposed to light of different wavelengths, or electron beams, ion beams, X-rays, etc., undergoes cross-linking or degradation in the exposed area, thereby altering its solubility and hydrophilicity / hydrophobicity in the developer. Taking a photoresist containing PBOCSt polymer resin as an example, after exposure to 248nm deep ultraviolet light and subsequent baking, the acid generated by the photoacid generator PAG catalyzes the deprotection of the tBOC protecting groups of the polymer resin, significantly changing the photoresist's solubility. Then, development is performed using a developer to dissolve and remove the deprotected portions, thereby achieving the transfer of the mask pattern. Currently, for PBOCSt fully protective photoresist, the common approach utilizes the hydrophilicity / hydrophobicity change of the polymer resin in the photoresist before and after photolithography, using an alkaline aqueous solution as the developer. However, the inventors found in practical use that using an alkaline aqueous solution as the developer resulted in poor adhesion between the PBOCSt photoresist and the silicon wafer, causing even un-illuminated areas to detach from the silicon substrate. Furthermore, using an alkaline aqueous solution as the developer typically requires 30 seconds of initial rinsing with the alkaline solution, followed by 30 seconds of rinsing with deionized water, resulting in a slow development speed. During experiments, it was observed that in addition to the hydrophilicity / hydrophobicity change, the PBOCSt fully protective photoresist also undergoes a polarity change before and after photolithography. Before deprotection, PBOCSt has very low polarity; after deprotection, phenolic hydroxyl groups are formed, resulting in higher polarity. The polarity of this photoresist significantly increases before and after photolithography. Utilizing this principle, the inventors attempted to replace the alkaline aqueous solution with an alcohol solvent, and surprisingly found that this not only effectively solved the poor adhesion problem but also significantly accelerated the development speed compared to traditional developing solutions.

[0033] Specifically, the present invention provides a method for improving photoresist adhesion and / or improving photoresist development speed, comprising the following steps:

[0034] (1) Photoresist is coated on the surface of a substrate to obtain a photoresist film; the photoresist includes a polymer resin, a photoacid generator and a solvent, wherein the polymer resin is a non-polar polymer resin or a weakly polar polymer;

[0035] (2) The photoresist film is exposed and baked after exposure using an exposure system. The polarity of the polymer resin in the photoresist in the exposed area increases before and after exposure, resulting in a photoresist film after photolithography.

[0036] (3) An alcohol solvent is used as a developing solution to develop the photoresist film after photolithography, thereby realizing the transfer of the mask pattern.

[0037] This invention is applicable to various photoresists, especially those that undergo physical or chemical changes during exposure, such as crosslinking or degradation, which increase the polarity of the polymer resin. The polymer resin includes, but is not limited to, PBOCSt (4-tert-butoxycarbonyloxystyrene homopolymer), 4-tert-butoxycarbonyloxystyrene copolymer, tert-butyl vinylbenzoate homopolymer or copolymer, tert-butyl acrylate homopolymer or copolymer, and tert-butyl methacrylate homopolymer or copolymer. Taking a photoresist containing PBOCSt polymer resin as an example, after exposure to 248nm deep ultraviolet light and subsequent baking, the acid generated by PAG catalyzes the deprotection of the tBOC protecting groups in the polymer resin, significantly changing the solubility of the photoresist. Simultaneously, PBOCSt has very low polarity before the tBOC protecting groups are deprotected by the acid generated by PAG; after deprotection, phenolic hydroxyl groups are formed, resulting in higher polarity. Therefore, the polarity of the photoresist increases before and after exposure.

[0038] The photoacid generator in the photoresist of the method of the present invention can be any type of photoacid generator, including but not limited to sulfonate photoacid generators, onium salt photoacid generators, etc. Sulfonate photoacid generators include, but are not limited to, oxime sulfonate compounds, n-hydroxyimide sulfonate compounds, nitrobenzyl sulfonate compounds, and general sulfonate compounds. Examples of oxime sulfonate compounds include 9H-fluorene-9-one, O-[(4-methylphenyl)sulfonyl]oxime, 9H-fluorene-9-one, and O-[(4-trifluoromethyl]oxime. [Phenyl]sulfonyl]oxime, etc.; n-hydroxyimide sulfonates such as N-hydroxynaphthaleneimide trifluoromethanesulfonate, N-hydroxynaphthaleneimide perfluorobutanesulfonate, etc.; nitrobenzyl sulfonates such as 2-nitrobenzyl p-toluenesulfonate, 2-nitrobenzyl trifluorotoluenesulfonate, 4,5-dimethoxy-2-nitrobenzyl p-toluenesulfonate, etc.; general sulfonates such as 2-phenyl-2-p-toluenesulfonyloxyacetophenone, 2-phenyl-2-trifluorotoluenesulfonyloxyacetophenone, etc. Onium salt photoacid-generating agents include, but are not limited to, triphenylsulfonium trifluoromethanesulfonate, triphenylsulfonium perfluorobutylsulfonate, and bis[4-(1,1-dimethylethyl)phenyl]trifluoromethanesulfonate iodonium salt, etc.

[0039] Similarly, the solvent used in the photoresist can be any organic solvent capable of dissolving the polymer resin and the photoacid generator, including but not limited to one or more of tetrahydrofuran, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, ethyl lactate, cyclohexanone, toluene, p-xylene, and acetone.

[0040] In some embodiments of the present invention, the mass ratio of polymer resin, photoacid generator and solvent is (5-15):(1-5):(80-200).

[0041] The method of this invention is applicable to various photoresist systems, and its exposure process can follow the exposure process commonly used in existing photoresist systems. In some embodiments, the photoresist film is baked at 70-100℃ for 0.5-1 min before exposure, and the exposure energy during exposure is 50-100 mJ / cm². 2 After exposure, bake at 80-120℃ for 50-200 seconds.

[0042] This invention addresses the polarity change of existing photoresist systems before and after exposure by proposing the use of alcohol-based solvents as developers. The alcohol solvent can be any small-molecule alcohol solvent that is liquid at room temperature (20-30°C). In some embodiments, the alcohol solvent is one or more selected from ethanol, propanol, isopropanol, n-butanol, isobutanol, sec-butanol, tert-butanol, and n-pentanol. Experiments have shown that using an alcohol solvent as the developer significantly accelerates the development speed compared to using an alkaline aqueous solution as the developer in existing technologies. In some embodiments, the development time is 1-60 seconds, preferably 5-20 seconds.

[0043] In step (3) of this invention, an alcohol solvent is used as the developing solution. After development, the residual alcohol solvent is purged with nitrogen gas. Unlike the prior art, which requires cleaning with an alkaline solution and then cleaning with deionized water to remove the residual alkaline developing solution, this invention does not require cleaning with an alkaline solution.

[0044] The polymer resin used in the embodiments of the present invention can be purchased commercially or prepared by oneself.

[0045] The following are specific examples:

[0046] Example 1

[0047] The photoresist was prepared according to the following formula: 10 parts by weight of PBOCSt resin, 2.5 parts by weight of the photoacid generator p-toluenesulfonic acid-4,5-dimethoxy-2-nitrobenzyl ester (CAS: 189627-26-7), and 100 parts by weight of tetrahydrofuran. The PBOCSt resin was prepared by the following method: 10 g of 4-tert-butoxycarbonyloxystyrene, 0.15 g of AIBN, and 5 mL of THF were added to a Schlenk flask, and the mixture was heated under reflux for 48 h under a nitrogen atmosphere, finally precipitated in petroleum ether.

[0048] Spin-coat the above photoresist solution onto a clean silicon wafer at a speed of 4000 rpm for 30 seconds to obtain a photoresist film.

[0049] Photolithography process conditions: Baking at 80℃ for 30 seconds, exposure energy: 100mJ / cm 2 After exposure, bake at 100℃ for 60 seconds, develop with ethanol for 5 seconds, and purge with nitrogen to remove residual developer.

[0050] The overall photolithography and the magnified local pattern are as follows: Figure 1 and Figure 2 As shown. From Figure 1 and Figure 2 As can be seen, the photoresist is intact, with uniform edges of independent lines and no adhesion. The photoresist in the exposed part of the channel can be completely developed and removed. It only takes 5 seconds of development to completely remove the exposed part, while the unexposed part remains intact.

[0051] Comparative Example 1

[0052] The other conditions are the same as in Example 1, except that the ethanol in Example 1 is replaced with a 2.38% TMAH (tetramethylammonium hydroxide) aqueous solution as the developing solution.

[0053] The overall photolithography and the magnified local pattern are as follows: Figure 3 and Figure 4 As shown. From Figure 3 and Figure 4 As can be seen, although the development time was 40 seconds and then the photoresist was rinsed with deionized water for 30 seconds, the photoresist was not intact overall, with some areas peeling off. After development, a large amount of photoresist remained in the exposed areas of the trench.

[0054] Example 2

[0055] Other conditions were the same as in Example 1, except that isopropanol was replaced with ethanol as the developer, and the development time was 10 seconds (the development effect of different development times was tested during the experiment, and the development effect was judged by metallographic microscope; the time to achieve the ideal development effect was the required development time). The overall lithography pattern and the magnified local pattern after 10 seconds of development are shown below. Figure 5 and Figure 6 As shown. From Figure 5 and Figure 6 As can be seen, the photoresist is intact, the edges of the independent lines are uniform, and there is no adhesion. The photoresist in the exposed part of the channel can be completely developed and removed, while the unexposed part is well preserved.

[0056] Example 3

[0057] Other conditions were the same as in Example 1, except that the ethanol in Example 1 was replaced with hexanol as the developer, and the development time was 20 seconds (the development effect of different development times was tested during the experiment, and the development effect was judged by metallographic microscope; the time to achieve the ideal development effect was the development time required). The overall lithography pattern and the magnified partial pattern after 20 seconds of development are shown below. Figure 7 and Figure 8 As shown. From Figure 7 and Figure 8As can be seen, the photoresist is intact, the edges of the independent lines are uniform, and there is no adhesion. The photoresist in the exposed part of the channel can be completely developed and removed, while the unexposed part is well preserved.

[0058] Comparing Examples 1, 2, and 3, it was found that, under the same conditions, using ethanol as the developer in Example 1 resulted in a better photoresist in a shorter time compared to isopropanol in Example 2 and n-hexanol in Example 3. This also indicates that different alcohol solvents have different development rates. However, in terms of both development effect and development speed, using alcohol solvents as developers is superior to using alkaline solution as the developer in Comparative Example 1.

[0059] Example 4

[0060] Other conditions were the same as in Example 1, except that PBOCSt in Example 1 was replaced with tert-butyl vinylbenzoate. The tert-butyl vinylbenzoate resin was prepared by adding 10 g of tert-butyl vinylbenzoate, 0.15 g of AIBN, and 5 mL of THF to a Schlenk flask, heating under reflux for 48 h in a nitrogen atmosphere, and finally precipitating in petroleum ether.

[0061] The overall photolithography and the magnified local pattern are as follows: Figure 9 and Figure 10 As shown. From Figure 9 and Figure 10 As can be seen, the photoresist is intact, the edges of the independent lines are uniform, and there is no adhesion. The photoresist in the exposed part of the channel can be completely developed and removed, while the unexposed part is well preserved.

[0062] Those skilled in the art will readily understand that the above description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method for improving adhesion and / or development speed of a photoresist, characterized by, The method comprises the following steps: (1) applying a photoresist on a surface of a substrate to obtain a photoresist film; the photoresist comprises a polymer resin, a photoacid generator and a solvent, the polymer resin is a nonpolar polymer resin or a weakly polar polymer resin; the polymer resin is selected from one or more of 4-tert-butoxycarbonyloxy styrene homopolymer, 4-tert-butoxycarbonyloxy styrene copolymer, vinylbenzoic acid tert-butyl ester homopolymer, vinylbenzoic acid tert-butyl ester copolymer, tert-butyl acrylate homopolymer, tert-butyl acrylate copolymer, tert-butyl methacrylate homopolymer and tert-butyl methacrylate copolymer; the photoacid generator is a sulfonate photoacid generator and / or an onium salt photoacid generator; (2) exposing the photoresist film by using an exposure system and performing post-exposure baking, the polymer resin in the photoresist in the exposed area increases in polarity after exposure to obtain a photoresist film after exposure; (3) developing the photoresist film after exposure by using an alcohol solvent as a developing solution to realize transfer of a mask pattern; the alcohol solvent is one or more of ethanol, propanol, isopropanol, n-butanol, isobutanol, sec-butanol, tert-butanol and n-pentanol; and after the developing process, the residual alcohol solvent is blown off by using nitrogen, and no fixing is needed, i.e. no deionized water is needed to remove the residual developing solution; the developing process has a developing time of 5-20 s.

2. The method of claim 1, wherein, The solvent in step (1) is one or more of tetrahydrofuran, propylene glycol monomethyl ether, propylene glycol monomethyl ether acetate, ethyl lactate, cyclohexanone, toluene, p-xylene and acetone.

3. The method of claim 1, wherein, Step (2) the photoresist film is baked at 70-100°C for 0.5-1 min before exposure, and the exposure energy during exposure is 50-100 mJ / cm 2 , and the film is baked at 80-120°C for 50-200 s after exposure.

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