Jul. 4, 2019  1  US 2019/0204738 Al  SUMMARY OF THE INVENTION  RESIST COMPOSITION AND METHOD OF  FORMING RESIST PATTERN  BACKGROUND OF THE INVENTION  Field of the Invention  Description of Related Art  DETAILED DESCRIPTION OF THE  INVENTION  [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.  [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.  [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.  [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]  [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.  [0008]  In order to further control acid diffusion, a method  of changing a polymer compound in various manners is  employed.  [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.  [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.  [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.  [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.  [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.  [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.  [0012]  In order to solve the above-described problems, the  present invention employs the following configurations.  [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.  [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.  [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.  (a0-1) 