Process solution composition for extreme ultraviolet lithography and method for forming pattern using same

Abstract

The present invention provides a method for improving pattern collapse that occurs during photoresist development in a fine pattern process using extreme ultraviolet light, a process solution composition, and a method for forming a high-quality photoresist pattern using the process solution composition. The process liquid composition includes: 0.0001 to 1 wt % of a nonionic surfactant having an HLB value of 9 to 16; 0.0001 to 1 wt % of tetrabutylammonium hydroxide; and 98 to 99.9998 wt % of water.

Description

[Technical field]

[0001] The present invention relates to a process solution composition for reducing the degradation of a polyhydroxystyrene-containing photoresist pattern used in extreme ultraviolet light exposure during a semiconductor manufacturing process, and a pattern formation method using the composition. [Background technology]

[0002] In the semiconductor manufacturing process, a light source with a smaller wavelength band is required to form finer patterns. Currently, lithography technology using extreme ultraviolet (EUV, extreme ultra violet, wavelength 13.5 nm) light sources is widely used, and it has become possible to realize finer patterns using this. However, since the etching resistance of extreme ultraviolet photoresists has not yet been improved, photoresist patterns with large aspects are continuously required, which makes it easy for pattern collapse during development, resulting in a problem of greatly reducing the process margin in the manufacturing process.

[0003] For this reason, there is a demand for technological development to improve the collapse that occurs during the formation of fine patterns. Although the best way to improve the level of pattern collapse would be to improve the performance of photoresists, the reality is that it is difficult to develop a new photoresist that satisfies all performance requirements. Even though the need for new development of superior photoresists has disappeared, efforts continue to be made to improve the level of pattern collapse in other ways. Summary of the Invention [Problem to be solved by the invention]

[0004] An object of the present invention is to develop a method and process solution composition for improving pattern collapse that occurs during photoresist development in a fine pattern process using extreme ultraviolet light. Another object of the present invention is to provide a method for forming a high quality photoresist pattern using such a process solution composition. [Means for solving the problem]

[0005] The present invention is a process solution composition for reducing the collapse of polyhydroxystyrene-containing photoresist patterns limited by extreme ultraviolet light exposure sources, and as a result of continued research and experiments focusing on the type, content and HLB value of nonionic surfactants, the type and content of alkaline substances, and the content of pure water, the problem was solved. Various surfactants are used in the aqueous cleaning solution used in the development process. In the present invention, as a result of various research focusing on the HLB (Hydrophilic-Lipophilic Balance) value, an effective cleaning solution was produced using a nonionic surfactant with an HLB value of 9 to 16. The HLB value is a typical method for classifying the properties of nonionic surfactants. The HLB value ranges from 0 to 20, with the closer the HLB value is to 0, the stronger the hydrophobic (lipophilic) properties of the nonionic surfactant, and the closer the HLB value is to 20, the stronger the hydrophilic properties of the nonionic surfactant.

[0006] When a non-ionic surfactant, which is nearly hydrophobic, is used in an aqueous cleaning solution that mainly uses ultrapure water, it can induce hydrophobicity of the photoresist wall surface, thereby reducing pattern melting and collapse. However, since non-ionic surfactants have a strong tendency to aggregate with each other, the physical properties of the cleaning solution become non-uniform, and the aggregated non-ionic surfactants may induce defects during use. In the present invention, it was confirmed that the smaller the HLB value of the nonionic surfactant, the better the effect of improving pattern collapse. However, it was also confirmed that when too much nonionic surfactant is used or the HLB value is 8 or less, the surfactants aggregate with each other in an aqueous type cleaning solution mainly using ultrapure water. On the other hand, when a nonionic surfactant that is close to hydrophilicity is used, it can be evenly dispersed without aggregation in an aqueous type cleaning solution that mainly uses ultrapure water, thereby producing a cleaning solution with uniform physical properties. The surfactant can be adsorbed onto the wall surface of the photoresist that has been partially hydrophilized after exposure and development, thereby reducing the capillary force and improving pattern collapse. However, if the surfactant is too hydrophilic, it may induce melting of the photoresist pattern, resulting in pattern collapse.

[0007] As a result of various research and experiments, the present inventors have confirmed that when the HLB value of a nonionic surfactant is 17 or more, the ability to reduce pattern collapse is insufficient. Currently, the typical developer used in most photolithography development processes is a mixture of pure water and tetramethylammonium hydroxide diluted to a certain concentration. In most processes, 2.38% by weight of tetramethylammonium hydroxide is mixed with 97.62% by weight of water, and even in extreme ultraviolet lithography processes, tetramethylammonium hydroxide is currently diluted in pure water and used as the developer. In the present invention, it was confirmed that when the substrate was continuously washed with pure water alone after development in the extreme ultraviolet lithography process, the pattern collapsed.

[0008] In addition, pattern collapse was also confirmed when, after development in the extreme ultraviolet lithography process, a cleaning solution containing tetramethylammonium hydroxide in pure water was continuously applied, or when a cleaning solution containing tetramethylammonium hydroxide in pure water was continuously applied after washing with pure water alone. Based on these results, it can be inferred that in the case of a cleaning solution containing tetramethylammonium hydroxide in pure water, the fine patterns exposed to extreme ultraviolet light are weakened, and the capillary force is strong or non-uniform, causing the patterns to collapse. In the present invention, in order to improve the collapse of the pattern exposed to extreme ultraviolet light and further improve the LWR (Line Width Roughness) and defects of the photoresist pattern required in the extreme ultraviolet light process, it was recognized that there was a need to search for an alkaline material that has a relatively weaker effect on the exposed pattern than tetramethylammonium hydroxide, and research and experiments on this subject were continuously conducted.

[0009] In the present invention, it was confirmed that when tetraethylammonium hydroxide, tetrapropylammonium hydroxide, or tetrabutylammonium hydroxide, other than tetramethylammonium hydroxide, was used among the alkaline substances, LWR or defects were improved without pattern collapse. Therefore, as a first preferred embodiment, the present invention provides a rinsing solution for reducing the level of pattern collapse occurring during photoresist development, comprising: 0.0001 to 1 wt % of an alkaline substance selected from the group consisting of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, or a mixture thereof; 0.0001 to 1 wt % of a nonionic surfactant having an HLB value of 9 to 16; and 98 to 99.9998 wt % of water.

[0010] The surfactant according to the embodiment may be a non-ionic surfactant. The non-ionic surfactant according to the above embodiment may be selected from the group consisting of polyoxyethylene alkyl ethers, polyoxypropylene alkyl ethers, polyoxyethylene oxypropylene alkyl ethers, or mixtures thereof. The polyoxyethylene alkyl ether, polyoxypropylene alkyl ether, and polyoxyethylene oxypropylene alkyl ether according to the above embodiment may have an HLB value of 9-16. The present invention also provides a method for forming a photoresist pattern, comprising: (a) applying a photoresist to a semiconductor substrate to form a film; (b) exposing the photoresist film to light and developing it to form a pattern; and (c) cleaning the photoresist pattern with the photolithography process liquid composition.

[0011] It is believed that the cause of pattern collapse is the capillary force that occurs between patterns when the patterns are washed with pure water after development, but it was confirmed that pattern collapse cannot be completely improved by simply reducing the capillary force. When an inappropriate surfactant is used in an excessive amount in order to lower the surface tension of the rinse solution to reduce the capillary force, it may induce melting of the pattern, which may further induce pattern collapse. In order to improve the pattern collapse, it is important to select a surfactant that reduces the surface tension of the cleaning solution and prevents the melting of the photoresist pattern. The cleaning solution of the present invention is highly effective for photoresists using extreme ultraviolet light sources, and is particularly effective in reducing the level of pattern collapse that occurs during development of photoresists whose main component, resin, is polyhydroxystyrene. Effect of the Invention

[0012] The process solution composition for photolithography of the present invention can be useful for forming a polyhydroxystyrene-containing photoresist pattern defined by an extreme ultraviolet light exposure source, and in particular, by adding a simple process, it can reduce production costs by showing a pattern collapse reduction effect that is difficult to achieve with photoresist alone. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] The present invention will now be described in more detail. The present invention relates to a process solution for reducing the level of pattern collapse occurring during photoresist development, comprising: 0.0001 to 1 wt % of an alkaline substance selected from the group consisting of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, or a mixture thereof; 0.0001 to 1 wt % of a nonionic surfactant having an HLB (Hydrophilic-Lipohilic Balance) value of 9 to 16; and 98 to 99.9998 wt % of water. Hereinafter, preferred examples and comparative examples of the present invention will be described. However, the following examples are merely preferred examples of the present invention and are not intended to limit the present invention.

[0014] [Example] Examples and Comparative Examples [Example 1] A process solution for reducing the degradation level of a photoresist pattern, containing 0.01% by weight of polyoxyethylene alkyl ether having an HLB value of 9 and 0.01% by weight of tetrabutylammonium hydroxide, was prepared in the following manner. 0.01 wt% of polyoxyethylene alkyl ether having an HLB value of 9 and 0.01 wt% of tetrabutylammonium hydroxide were added to 99.98 wt% of distilled water, stirred for 5 hours, and then passed through a 0.01 μm filter to remove fine solid impurities, thereby preparing a process solution for reducing the level of degradation of the photoresist pattern. [Examples 2 to 20] According to the compositions shown in Tables 1 to 5, process solutions for reducing the degradation level of the photoresist pattern, which is the same as in Example 1, were prepared.

[0015] [Comparative Example 1] Pure water (distilled water) which is generally used as a final process liquid in a development process in a semiconductor device manufacturing process was prepared. [Comparative Examples 2 to 9] According to the compositions shown in Tables 1 to 5, process solutions were prepared in the same manner as in Example 1 for comparison with the examples. [Table 1] [Table 2] [Table 3] [Table 4] [Table 5]

[0016] Experimental and comparative examples The patterns formed by the steps of applying a photoresist to a semiconductor substrate to form a film, and exposing and developing the photoresist film to form a pattern were cleaned using the process liquid compositions prepared in Examples 1 to 20 and Comparative Examples 1 to 9, and then the pattern collapse level and the reduction ratio of the number of defects were measured for the silicon wafers on which the patterns were formed, and the results are shown in Table 6 as Experimental Examples 1 to 20 and Comparative Experimental Examples 1 to 9.

[0017] (1) Check to see if the pattern collapses After splitting the exposure energy and focus, the number of blocks in which the pattern did not collapse was measured out of a total of 89 blocks using a critical dimension scanning electron microscope (CD-SEM, Hitachi, Ltd.). (2) Proportion of defects Using a surface defect observation device [manufactured by KLA Tencor], the number of defects (A) was counted for the photoresist patterns rinsed with each rinse solution sample, and expressed as a percentage (%) of the number of defects (B) when rinsed with pure water only, i.e., (A / B) x 100. The number of defects after processing with pure water only is set as 100%, and the degree of decrease or increase in the number of defects compared to 100% when processing with pure water only is expressed as a percentage. The lower this value, the better the product. (3) Transparency The transparency of the prepared cleaning solutions was checked with the naked eye and was indicated as transparent or opaque. [Table 6]

[0018] Comparing Experimental Examples 1 to 8 with Comparative Experimental Examples 1 to 3, it was confirmed that the number of blocks without pattern collapse increased, the number of defects decreased, and all were transparent when the HLB value of the surfactant was 9 to 16. In particular, it was confirmed that an even more excellent effect was observed when the HLB value was 9 to 13. Comparing Experimental Examples 2 and 9 to 12 with Comparative Experimental Examples 4 and 5, it was confirmed that when the surfactant content was 0.0001 to 1 wt %, the number of blocks without pattern collapse increased, the number of defects decreased, and all were transparent. Comparing Experimental Examples 2 and 13 to 16 with Comparative Experimental Examples 6 and 7, it was confirmed that when the content of the alkaline substance was 0.0001 to 1 wt %, the number of blocks without pattern collapse increased, the number of defects decreased, and all were transparent.

[0019] Comparing Experimental Examples 2, 17, and 18 with Comparative Experimental Example 1, it was confirmed that when the surfactant was polyoxyethylene alkyl ether, polyoxypropylene alkyl ether, or polyoxyethyleneoxypropylene alkyl ether, the number of blocks without pattern collapse increased, the number of defects decreased, and all were transparent. In particular, it was confirmed that an even more excellent effect was observed when the surfactant was polyoxyethylene alkyl ether. Comparing Experimental Examples 2, 19, and 20 with Comparative Experimental Examples 8 and 9, it was confirmed that when the alkaline substance was tetraethylammonium hydroxide, tetrapropylammonium hydroxide, or tetrabutylammonium hydroxide, the number of blocks without pattern collapse increased, the number of defects decreased, and all were transparent. In particular, it was confirmed that an even more excellent effect was observed when the alkaline substance was tetrabutylammonium hydroxide. On the other hand, the pattern collapse evaluation result of Example 2 showed that the number of sections (blocks) in which pattern collapse did not occur was 77, demonstrating an extremely excellent effect. In contrast, the pattern collapse evaluation result for Comparative Example 1 confirmed that the number of sections (blocks) in which pattern collapse did not occur was 46, indicating a poor effect.

[0020] Although the specific parts of the present invention have been described in detail above, it is clear to those skilled in the art that such specific descriptions are merely preferred embodiments and do not limit the scope of the present invention. Therefore, the substantial scope of the present invention should be defined by the appended claims and their equivalents.

Claims

1. A process solution composition for reducing the degradation of a polyhydroxystyrene-containing photoresist pattern defined by an extreme ultraviolet light exposure source, comprising: 0.0001 to 1% by weight of a nonionic surfactant having an HLB value of 9 to 13; 0.0001 to 1% by weight of tetrabutylammonium hydroxide; and 98 to 99.9998% by weight of water; When one or more of tetraethylammonium hydroxide and tetrapropylammonium hydroxide are contained, the total content of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide is 1% by weight or less; The process liquid composition, wherein the nonionic surfactant is a polyoxyethylene alkyl ether.

2. (a) applying a photoresist to a semiconductor substrate to form a film; (b) exposing the photoresist film to light and then developing it to form a pattern; (c) cleaning the photoresist pattern with the photolithography process liquid composition according to claim 1.

3. 3. The method of claim 2, wherein the exposure source is extreme ultraviolet light.

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