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## RESIST COMPOSITION AND METHOD OF FORMING RESIST PATTERN 

## BACKGROUND OF THE INVENTION 

[0001] The present invention relates to a resist composi› tion and a method of forming a resist pattern. 

[0002] Priority is claimed on Japanese Patent Application No. 2017-254665, filed on Dec. 28, 2017, the content of which is incorporated herein by reference. 

[0003] In lithography techniques, for example, a resist film formed of a resist material is formed on a substrate, and the resist film is subjected to selective exposure, followed by a development treatment, thereby forming a resist pattern having a predetermined shape on the resist film. A resist material in which the exposed portions of the resist film become soluble in a developing solution is called a positive type, and a resist material in which the exposed portions thereof become insoluble in a developing solution is called a negative type. 

[0004] In recent years, in the production of semiconductor elements and liquid crystal display elements, advances in lithography techniques have led to rapid progress in the field of pattern miniaturization. Typically, these miniaturization techniques involve shortening the wavelength (increasing the energy) of the exposure light source. 

[0005] Conventionally, ultraviolet radiation typified by g-line and i-line radiation has been used, but nowadays KrF excimer lasers and ArF excimer lasers are used in mass production. Furthermore, research is also being conducted into lithography techniques that use an exposure light source having a wavelength shorter (energy higher) than these excimer lasers, such as electron beams (EB), extreme ultra› violet radiation (EUV), and X rays. 

[0006] Recently, in EUV lithography or EB lithography, a chemically amplified resist which has been suggested to be used for KrF excimer laser or ArF excimer laser has been usually used as the resist material since lithography charac› teristics such as the sensitivity with respect to EUV or EB or the resolution that enables formation of a fine target resist pattern are excellent. Particularly, it is considered that the chemically amplified resist containing an acrylic resin as a base resin has excellent lithography characteristics described above. 

[0007] For example, EUV exposure has a problem of acid diffusion control. In order to control acid diffusion, the anion structure of an acid generator is usually changed, and an acid generator having an anion structure in which the diffusion length of an acid is short diffusion is already applied. 

[0008] In order to further control acid diffusion, a method of changing a polymer compound in various manners is employed. 

[0009] For example, PCT International Publication No. WO2010/095698 describes a resist composition which employs a polymer compound containing a specific acid dissociable functional group and improves the reactivity with respect to an acid to contribute to improvement of the solubility in a developing solution. 

## Field of the Invention 

## Description of Related Art 

[0010] With further progress of lithography techniques and further promotion of miniaturization of a resist pattern, there has been a growing demand for a resist material to form a resist pattern with higher resolution while maintain› ing excellent lithography characteristics. 

[0011] The present invention has been made in consider› ation of the above-described problems, and an object thereof is to provide a resist composition in which various lithog› raphy characteristics are favorably balanced and the resolu› tion and roughness are improved; and a method of forming a resist pattern obtained by using the resist composition. 

[0012] In order to solve the above-described problems, the present invention employs the following configurations. 

[0013] In other words, according to a first aspect of the present invention, there is provided a resist composition which generates an acid upon exposure and whose solubility in a developing solution is changed due to an action of the acid, the resist composition including: a resin component (Al) whose solubility in a developing solution is changed due to the action of the acid, in which the resin component (Al) has a constitutional unit (a0) derived from a compound represented by Formula (a0-1) and a constitutional unit (al) (where a constitutional unit corresponding to the constitu› tional unit (a0) is excluded) containing an acid decompos› able group whose polarity is increased due to the action of the acid. 

[0014] [In the formula, W represents a polymerizable group-containing group, Ya 0 represents a carbon atom, Xa 0 represents a group that forms a monocyclic aliphatic hydro› carbon group together with Ya 0, some or all hydrogen atoms in the monocyclic aliphatic hydrocarbon group may be substituted with substituents, and Ra$^{00 }$represents an aro› matic hydrocarbon group which may have a substituent] 

[0015] According to a second aspect of the present inven› tion, there is provided a method of forming a resist pattern, including: a step of forming a resist film on a support using the resist composition according to the first aspect; a step of exposing the resist film; and a step of developing the exposed resist film to form a resist pattern. 

[0016] According to the present invention, it is possible to provide a resist composition in which various lithography characteristics are favorably balanced and the resolution and roughness are improved; and a method of forming a resist pattern obtained by using the resist composition. 

[0017] In the present description and claims, the term "aliphatic" is a relative concept used in relation to the term "aromatic", and defines a group or compound that has no aromaticity. 

## SUMMARY OF THE INVENTION 

## DETAILED DESCRIPTION OF THE INVENTION 

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