Patent Application
20220251472
The present invention relates to a process liquid composition for alleviating a lifting defect level of a photoresist pattern and for reducing the number of defects of the photoresist pattern, the photoresist pattern having hydrophobicity represented by a contact angle of 70° or greater of water with respect to a photoresist surface in a photoresist pattern process, and to a method of forming a photoresist pattern using the process liquid composition.
Generally, a semiconductor is manufactured by a lithographic process in which exposure light is infrared light in a wavelength of 193 nm, 248 nm, 365 nm, or the like. There is intense competition among semiconductor manufacturers for reduction in a critical dimension (hereinafter referred to as a CD).
Accordingly, the finer pattern is to be formed, the narrower wavelength a light source needs to produce. At the present time, a lithographic technology using an extreme ultraviolet (EUV in a wavelength of 13.5 nm) is actively employed. A narrower wavelength may be realized using this lithographic technology.
However, the resistance of EUV photoresist to etching is not yet improved, and thus a photoresist pattern having a high aspect ratio still needs to be used. Accordingly, a pattern lifting defect occurs easily during development, and the number of defects is increased. Consequently, a process margin is greatly reduced in a manufacturing process.
To solve this problem, there is a demand to develop the technology for alleviating a level of a lifting defect that occurs while forming a fine pattern and for reducing the number of defects. The best way to alleviate a pattern lifting defect level and reduce the number of defects may be to improve photoresist performance. However, there is a need to consider a situation where, in practice, it is difficult to develop new photoresist having performance that is satisfactory in terms of all aspects.
There is still a need to develop new photoresist. However, attempts have been made to alleviate the pattern lifting defect level and reduce the number of defects in ways other than addressing this need.
An objective of the present invention is to develop a process liquid composition for alleviating a level of a pattern lifting defect and reducing the number of defects, the pattern lifting defect occurring after developing photoresist having hydrophobicity represented by a contact angle of 70° or greater of water with respect to a photoresist surface, and to develop a method of forming a photoresist pattern using the process liquid composition.
Various surfactants are used to manufacture a water-based process liquid composition that is used during a developing process. However, according to the present invention, an effective process liquid composition was manufactured using a fluorine-based surfactant and a hydrocarbon-based anionic surfactant.
The use of a hydrocarbon-based non-ionic surfactant with a property like hydrophobicity in manufacturing the water-based process liquid composition in which ultra-pure water is mostly contained may lead to forming a hydrophobic sidewall of a photoresist and thus reducing pattern melting or collapse. However, in this case, the hydrocarbon-based non-ionic surfactants have a strong tendency to agglomerate, resulting in preventing a property of the process liquid composition from being uniform. Theretofore, there is a likelihood that the agglomerating hydrocarbon-based non-ionic surfactants will cause a defect while the process liquid composition is in use. That is, the use of the hydrocarbon-based non-ionic surfactant requires an increase in the usage amount thereof for reducing the pattern melting. Thus, there is a concern that photoresist will be damaged. In addition, the excessive use of an unsuitable surfactant for the purpose of reducing surface tension of the process liquid composition to reduce a capillary force may lead to the pattern melting and rather may further cause the pattern collapse.
In addition, in the case of a hydrocarbon-based cationic surfactant, an active group dissociates into a cation in an aqueous solution, and it is rarely ensured that metal is formed. Thus, there is a concern that a serious defect will be caused to occur in a lithographic process.
According to the present invention, it was verified that the use of the fluorine-based surfactant and the hydrocarbon-based anionic surfactant achieved the noticeable effect of alleviating the pattern lifting defect level and reducing the number of defects. The surface tension and the contact angle, which were much more decreased than in the hydrocarbon-based non-ionic surfactant, increased penetrability and spreadability, leading to contribution to formation of a fine pattern. It was recognized that this contribution resulted in the noticeable effect.
Tetramethylammonium hydroxide is diluted with pure water to a predetermined concentration (2.38% by weight of tetramethylammonium hydroxide is mixed with 97.62% by weight of water for use in most of the photolithographic developing processes) for use as a representative developing solution that is currently used in most of the photolithographic developing processes.
It was verified that a pattern lifting defect was caused in a case where, in a photolithographic process, a photoresist pattern having hydrophobicity represented by a contact angle of 70° or greater of water with respect to a photoresist surface was successively cleaned only with pure water after being developed. Furthermore, it was verified that, in the photolithographic process, the pattern collapse was also caused in a case where a process liquid composition resulting from tetramethylammonium hydroxide being contained in pure water was successively applied after developing or in a case where pure water was successively applied.
It could be estimated that the pattern collapse was caused because the process liquid composition containing tetramethylammonium hydroxide weakened the exposed fine pattern and because the capillary force was great and was non-uniform.
Therefore, in order to prevent the exposed-pattern collapse and to reduce the line width roughness (LWR) and the number of defects additionally required in a process, there is a need to conduct a study on an alkali substance that exerts a relatively weaker force on the exposed pattern than tetramethylammonium hydroxide.
According to the present invention, it was verified that, in a case where tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide was used among alkali substances, not only was the pattern collapse prevented and the LWR, but the number of defects was also reduced.
According to a desirable first embodiment of the present invention, there is provided a process liquid composition for alleviating a level of a lifting defect of a photoresist pattern and for reducing the number of lifting defects of the photoresist pattern, the composition containing a surfactant and having a surface tension of 40 millinewton/meter (mN/m= 1/1000 newton/meter) or less and a contact angle of 60° or smaller in the photoresist pattern having hydrophobicity represented by a contact angle of 70° or greater of water with respect to a photoresist surface in a photoresist pattern process.
According to a more desirable second embodiment of the present invention, there is provided a process liquid composition for alleviating a level of a lifting defect of a photoresist pattern and for reducing the number of lifting defects of the photoresist pattern, the lifting defect occurring during photoresist developing, the process liquid composition containing: 0.00001 to 0.1% by weight of a fluorine-based surfactant; 0.0001 to 0.1% by weight of a hydrocarbon-based anionic surfactant; 0.0001 to 0.1% by weight of an alkali substance; and 99.7 to 99.99979% by weight of water.
According to the most desirable third embodiment of the prevent invention, there is a process liquid composition for alleviating a level of a lifting defect of a photoresist pattern and for reducing the number of lifting defects of the photoresist pattern, the lifting defect occurring during photoresist developing, the process liquid composition containing: 0.00001 to 0.1% by weight of a fluorine-based surfactant; 0.001 to 0.1% by weight of a hydrocarbon-based anionic surfactant; 0.001 to 0.1% by weight of an alkali substance; and 99.7 to 99.9979% by weight of water, the composition having a surface tension of 40 mN/m or less and a contact angle of 60° or smaller.
In the process liquid composition according to any one of the first to third embodiments, the fluorine-based surfactant may be selected from the group consisting of fluoroacryl carboxylate, fluoroalkyl ether, fluoroalkylene ether, fluoroalkyl sulfate, fluoroalkyl phosphate, fluoroacryl co-polymer, fluoro co-polymer, perfluorinated acid, perfluorinated carboxylate, perfluorianted sulfonate, and mixtures thereof.
In the process liquid composition according to any one of the second to third embodiments, wherein the hydrocarbon-based anionic surfactant may be selected from the group consisting of ammonium salt of polycarboxylic acid, sulfonate salt, sulfate ester salt, phosphoric acid ester salt, and mixtures thereof.
In the process liquid composition according to any one of the first to third embodiments, wherein the alkali substance may be selected from the group consisting of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, and mixtures thereof.
According to an aspect of the present invention, there is provided a method of forming a photoresist pattern, the method including: (a) a step of dispensing photoresist on a semiconductor substrate and forming a photoresist film; (b) a step of exposing the photoresist film to light, developing the photoresist film, and forming a photoresist pattern; and (c) a step of cleaning the photoresist pattern with the process liquid composition.
It was thought that the pattern collapse was caused by the capillary force occurring between patterns when the patterns were cleaned with pure water after developing. However, it was experimentally recognized that only the reduction of the capillary force could neither completely prevent the pattern collapse nor reduce the number of the lifting defects.
The excessive use of the unsuitable surfactant for the purpose of reducing the surface tension of the process liquid composition to reduce the capillary force may lead to the pattern melting and rather may further cause the pattern collapse or increase the number of lifting defects.
In order to alleviate the level of the pattern lifting defect and reduce the number of the pattern lifting defects, it is important to select a surfactant that reduces the surface tension of the process liquid composition and at the same time prevents the melting of the photoresist pattern.
The process liquid composition according to the present invention exerts an enhancing effect on the photoresist and particularly achieves the effect of alleviating the level of the pattern lifting defect and the number of the pattern lifting defects, the pattern lifting defect occurring while developing photoresist having hydrophobicity represented by a contact angle of 70° or greater of water with respect to a photoresist surface.
The process liquid composition according to the present invention achieves the effect of alleviating the level of the pattern lifting defect and the number of the pattern lifting defects, the effect that cannot be achieved only with photoresist when a pattern is formed using the photoresist having hydrophobicity represented by a contact angle of 70° or greater of water with respect to a photoresist surface. The photoresist forming method including the step of cleaning the photoresist pattern with the process liquid composition can achieve the effect of greatly reducing manufacturing cost.
The present invention will be described in more detail below.
The present invention, which is the result of conducting much research over a long period of time, relates to a “process liquid composition for alleviating a lifting defect level of a photoresist pattern and reducing the number of defects of the photoresist, the process liquid composition containing: 0.00001 to 0.1% by weight of a fluorine-based surfactant selected from the group consisting of fluoroacryl carboxylate, fluoroalkyl ether, fluoroalkylene ether, fluoroalkyl sulfate, fluoroalkyl phosphate, fluoroacryl co-polymer), fluoro co-polymer, perfluorinated acid, perfluorinated carboxylate, perfluorianted sulfonate, and mixtures thereof; 0.0001 to 0.1% by weight of an anionic surfactant selected from the group consisting of ammonium salt of polycarboxylic acid, sulfonate salt, sulfate ester salt, phosphoric acid ester salt, and mixtures thereof; 0.0001 to 0.1% by weight of an alkali substance selected from the group consisting of tetraethylammonium hydroxide, tetrapropylammonium hydroxide, tetrabutylammonium hydroxide, and mixtures thereof; and 99.7 to 99.99979% by weight of water”. Composition components of the process liquid composition according to the present invention and a composition ratio between the components thereof were specified as shown in Embodiments 1 to 60. Composition components and a composition ratio that were in contrast with the above-mentioned composition components and composition ratio, respectively, were specified as shown in Comparative Examples 1 to 12.
Desired embodiments of the present invention and comparative examples for comparison therewith will be described below. However, the desired embodiments described below of the present invention are only exemplary, and the present invention is not limited thereto.
A process liquid composition for alleviating a collapse level of a photoresist pattern, which contains 0.001% by weight of fluoroacryl carboxylate, 0.01% by weight of ammonium salt of polycarboxylic acid, and 0.005% by weight of tetrabutylammonium hydroxide, was manufactured using the following method.
0.001% by weight of fluoroacryl carboxylate, 0.01% by weight of ammonium salt of polycarboxylic acid, and 0.005% by weight of tetrabutylammonium hydroxide were added into a remaining amount of distilled water and stirred for 5 hours. Then, the resulting liquid was caused to pass through a filter with a size of 0.01 μm to remove fine-sized soluble-solid impurities. In this manner, the process liquid composition for alleviating the collapse level of the photoresist pattern was manufactured.
Process liquid compositions for alleviating a defect level of a photoresist pattern that was the same as a defect level of a photoresist pattern in Embodiment 1 were manufactured according to composition components and component ratios therebetween that were specified as shown in Tables 1 to 12.
Usually, distilled water that was to be used as a cleaning solution in the last process among semiconductor manufacturing processes was prepared.
For comparison with embodiments, process liquid compositions were manufactured, as in Embodiment 1, according to the composition components and the component ratios therebetween that were specified as shown in Tables 1 to 12.
Measurements of pattern lifting defect levels and number-of-defects reduction ratios were performed on silicon wafers, patterns on which were formed in Embodiments 1 to 60 and Comparative Examples 1 to 12. The measurements are described as Experimental Examples 1 to 60 and Comparative Experimental Examples 1 to 12. The results of the measurements are shown in Table 13.
(1) Verification of Pattern Lifting Prevention
After exposure energy and focus were split, among a total of 89 blocks, the number of blocks in which a pattern did not collapse was measured using a critical dimension-scanning electron microscope (CD-SEM, manufactured by Hitachi, Ltd).
(2) Number-of-Lifting-Defects Reduction Ratio
Counting of the number A of defects was performed on a photoresist pattern that was rinsed with each process liquid composition sample, using surface defect observation equipment (manufactured by KLA-Tencor Corporation). A value of 100 was assigned to the number B of defects that resulted when the photoresist pattern was rinsed only with pure water. Then, the number A of defects was expressed as a ratio to the number B of defects, that is, as (AB)×100.
The number of defects that resulted when rinsing was performed only with pure water was defined as 100. The degree to which the number of defects was decreased (improved) or increased (degraded) when compared with the number of defects resulting from rinsing only with pure water was expressed as a reduction ratio.
(3) Transparency
Transparency of the manufactured process liquid composition was checked with the naked eye and was marked as a transparent or opaque process liquid composition.
(4) Surface Tension and Contact Angle
A surface tension and a contact angle of each of the process liquid compositions were measured using a surface tension measuring instrument [the K100 Force Tensiometer manufactured by KRÜSS GmbH] and a contact angle measuring instrument [the DSA-100 Drop Shape Analyzer manufactured by KRÜSS GmbH].
Measurements of the pattern lifting defect level, the number-of-defects reduction ratio, the transparency, the contact angle, and the surface tension were performed on the silicon wafers, the patterns on which were formed in Embodiments 1 to 60 and Comparative Examples 1 to 12. The measurements are described as Experimental Examples 1 to 60 and Comparative Experimental Examples 1 to 12. The results of the measurements are shown in Table 13.
(1) Verification of Pattern Lifting Prevention
After exposure energy and focus were split, among a total of 89 blocks, the number of blocks in which a pattern dis not collapse was measured using the critical dimension-scanning electron microscope (CD-SEM, manufactured by Hitachi, Ltd).
(2) Number of Lifting Defects
Counting of the number A of defects was performed on a photoresist pattern that was rinsed with each process liquid composition sample, using the surface defect observation equipment (manufactured by KLA-Tencor Corporation). A value of 100 was assigned to the number B of defects that resulted when the photoresist pattern was rinsed only with pure water. Then, the number A of defects was expressed as a ratio to the number B of defects, that is, as (AB)×100.
(3) Transparency
Transparency of the manufactured process liquid composition was checked with the naked eye and was marked as a transparent or opaque process liquid composition.
(4) Contact Angle and Surface Tension
A surface tension and a contact angle of each of the process liquid compositions were measured using the contact angle measuring instrument [the DSA-100 Drop Shape Analyzer manufactured by KRÜSS GmbH] and the surface tension measuring instrument [the K100 Force Tensiometer manufactured by KRÜSS GmbH].
From the comparison of Experimental examples 1 to 60 with Comparative Experimental examples 1 to 12, it could be seen that, when the number of blocks in which a pattern did not collapse was 50 or greater and the number-of-defects reduction ratio was 90% or less, a more improved result were obtained than in Comparative Experimental Example 1.
It could be seen that the pattern lifting defect level was much more alleviated and the number of defects was much more reduced in Experimental Examples 1 to 60 than in Comparative Experimental Examples 1 to 12. The process liquid composition that was used in Experimental Examples 1 to 60 contained: 0.00001 to 0.1% by weight of a fluorine-based surfactant selected from among fluoroacryl carboxylate, fluoroalkyl ether, fluoroalkylene ether, fluoroalkyl sulfate, fluoroalkyl phosphate, fluoroacryl co-polymer, fluoro co-polymer, perfluorinated acid, perfluorinated carboxylate, and perfluorianted sulfonate; 0.0001 to 0.1% by weight of an anionic surfactant selected from among polycarboxylate salt, sulfonate salt, sulfate ester salt, and phosphoric acid ester salt; 0.0001 to 0.1% by weight of an alkali substance selected from among tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide; and 99.7 to 99.99979% by weight of water.
In addition, it could be seen that, desirably, effects of alleviating the pattern lifting defect level and reducing the number of defects was much more increased in the experimental examples 1 to 60 than in Comparative Experimental Examples 1 to 12. The process liquid composition that was used in Experimental Examples 1 to 60 contained: 0.0001 to 0.1% by weight of a fluorine-based surfactant selected from among fluoroacryl carboxylate, fluoroalkyl ether, fluoroalkylene ether, fluoroalkyl sulfate, fluoroalkyl phosphate, fluoroacryl co-polymer, fluoro co-polymer, perfluorinated acid, perfluorinated carboxylate, and perfluorianted sulfonate; 0.001 to 0.1% by weight of a hydrocarbon-based anionic surfactant selected from among polycarboxylate salt, sulfonate salt, sulfate ester salt, and phosphoric acid ester salt; 0.001 to 0.1% by weight of an alkali substance selected from among tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide; and 99.7 to 99.9979% by weight of water.
In addition, it could be seen that, more desirably, effects of alleviating the pattern lifting defect level and reducing the number of defects was much more increased in the experimental examples 1 to 60 than in Comparative Experimental Examples 1 to 12. The process liquid composition that was used in Experimental Examples 1 to 60 contained: 0.001 to 0.1% by weight of a fluorine-based surfactant selected from among fluoroacryl carboxylate, fluoroalkyl ether, fluoroalkylene ether, fluoroalkyl sulfate, fluoroalkyl phosphate, fluoroacryl co-polymer, fluoro co-polymer, perfluorinated acid, perfluorinated carboxylate, and perfluorianted sulfonate; 0.01 to 0.1% by weight of a hydrocarbon-based anionic surfactant selected from among polycarboxylate salt, sulfonate salt, sulfate ester salt, and phosphoric acid ester salt; 0.01 to 0.1% by weight of an alkali substance selected from among tetraethylammonium hydroxide, tetrapropylammonium hydroxide, and tetrabutylammonium hydroxide; and 99.7 to 99.979% by weight of water.
The result of measuring the collapse level of the photoresist pattern in Embodiment 1 for evaluation, was that the number of blocks in which the pattern did not collapse was 80.
The result of measuring the collapse level of the photoresist pattern in Comparative Experimental Example 1 for evaluation, was that the number of blocks in which the pattern did not collapse was 46.
The specific aspects of the present invention are described in detail above. It would be apparent to a person of ordinary skill in the art to which the present invention pertains that this specific description is only for the desired embodiments and do not impose any limitation on the scope of the present invention. Therefore, a substantial scope and a scope equivalent thereto must be defined by the following claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10-2019-0086818 | Jul 2019 | KR | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/KR2020/008141 | 6/24/2020 | WO |
