US 9,164,380 B2  6  5  The term "base component" refers to an organic compound  capable of forming a film, and is preferably an organic com› pound having a molecular weight of 500 or more. When the  organic compound has a molecular weight of 500 or more, the  film-forming ability is improved, and a nano level resist pat› tern can be more easily formed.  The organic compounds having a molecular weight of 500  or more that can be used as the base component can be  broadly classified into non-polymers and polymers.  In general, compounds which have a molecular weight of at  least 500 but less than 4,000 may be used as non-polymers.  Hereafter, the term "low molecular weight compound" is  used to describe a non-polymer having a molecular weight of  at least 500 but less than 4,000.  In terms of the polymers, typically, compounds which have  a molecular weight of 1,000 or more may be used. In the  following description, the term "polymeric compound" is  used to describe a polymer having a molecular weight of  1,000 or more. In the case of a polymeric compound, the  "molecular weight" refers to the weight-average molecular  weight in terms of the polystyrene-equivalent value deter› mined by gel permeation chromatography (GPC). Hereafter,  a polymeric compound may be simply referred to as a "resin".  As the component (A), a resin component which exhibits  changed solubility in a developing solution under the action  of acid may be used, a low molecular weight compound  which exhibits changed solubility in a developing solution  under the action of acid may be used, or a combination of the  two may be used.  In those cases where the resist composition of the present  invention is a resist composition that forms a negative-type  pattern in an alkali developing process, a base component that  is soluble in an alkali developing solution is typically used as  the component (A), and a cross-linking agent is also added to  the composition.  The base component that is soluble in an alkali developing  solution contains alkali-soluble groups such as a hydroxyl  group, carboxyl group or sulfonamide group, and the cross› linking agent has a reactive group that is capable of reacting  with these alkali-soluble groups. Accordingly, in this resist  composition, when acid is generated from the component (B)  upon exposure, the action of the acid causes cross-linking  between the base component and the cross-linking agent, and  the cross-linked portions become insoluble in an alkali devel› oping solution. As a result, during resist pattern formation, by  conducting selective exposure of a resist film obtained by  applying the resist composition to a substrate, the exposed  portions change to a state that is insoluble in the alkali devel› oping solution, while the unexposed portions remain soluble  in the alkali developing solution, meaning alkali developing  can be used to form a resist pattern.  Generally, a resin that is soluble in an alkali developing  solution (hereafter referred to as an "alkali-soluble resin") is  used as the base component that is soluble in an alkali devel› oping solution.  Examples of the alkali-soluble resin include a resin having  a structural unit derived from at least one of an a-(hydroxy› alkyl)acrylic acid and an alkyl ester of an a-(hydroxyalkyl)  acrylic acid (preferably an alkyl ester having 1 to 5 carbon  atoms), as disclosed in Japanese Unexamined Patent Appli- cation, First Publication No. 2000-206694; an acrylic resin or  polycycloolefin resin having a sulfonamide group, and in  which an atom other than a hydrogen atom or a substituent  may be bonded to the carbon atom on the a-position, as  disclosed in U.S. Pat. No. 6,949,325; an acrylic resin contain- ing a fluorinated alcohol, and in which an atom other than a  hydrogen atom or a substituent may be bonded to the carbon  Further, in those cases where a solvent developing process  is used, the component (AO) exhibits good solubility in an  organic developing solution prior to exposure, but when acid  is generated from the component (B) upon exposure, the  action of the acid causes an increase in the polarity of the  component (AO) that reduces the solubility in the organic  developing solution. Accordingly, during resist pattern for› mation, by conducting selective exposure of a resist film  obtained by applying the resist composition to a substrate, the  exposed portions change from being soluble in an organic  developing solution to being substantially insoluble, while  the unexposed portions remain soluble in an organic devel› oping solution, and therefore developing with an organic  developing solution can be used to achieve contrast between  the exposed portions and the unexposed portions, and a nega- In those cases where an alkali developing process is used,  the component (AO) is substantially insoluble in an alkali  developing solution prior to exposure, but when acid is gen› erated from the component (B) upon exposure, the action of  the acid causes an increase in the polarity of the component  (AO) that increases the solubility in the alkali developing  solution. Accordingly, during resist pattern formation, by  conducting selective exposure of a resist film obtained by  applying the resist composition to a substrate, the exposed  portions change from being substantially insoluble in an  alkali developing solution to being soluble, while the unex› posed portions remain substantially insoluble in an alkali  developing solution, and therefore a contrast is achieved  between the exposed portions and the unexposed portions,  and a positive-type pattern can be formed by performing  developing with an alkali developing solution.  In those cases where the resist composition of the present  invention is a resist composition which forms a positive-type  pattern in an alkali developing process, but forms a negative› type pattern in a solvent developing process, a base compo› nent (AO) (hereafter referred to as "component (AO)") which  exhibits increased polarity under the action of acid is prefer- ably used as the component (A). By using the component  (AO), the polarity of the base component changes upon expo› sure, and therefore favorable developing contrast can be  achieved, not only in an alkali developing process, but also in  a solvent developing process.  As the cross-linking agent, usually, an amino-based cross› linking agent such as a glycoluril having a methylol group or  alkoxymethyl group, or a melamine-based cross-linking  agent is preferable, as it enables formation of a resist pattern  with minimal swelling. The amount added of the cross-link› ing agent is preferably within a range from 1 to 50 parts by  weight, relative to 100 parts by weight of the alkali-soluble  resm.  The term "a-(hydroxyalkyl)acrylic acid" refers to, in an  acrylic resin in which an atom other than a hydrogen atom or  a substituent may be bonded to the carbon atom on the a-po› sition, one or both of acrylic acid in which a hydrogen atom is  bonded to the carbon atom on the a-position having the  carboxyl group bonded thereto, and a-hydroxyalkyl acrylic  acid in which a hydroxyalkyl group (preferably a hydroxy› alkyl group of 1 to 5 carbon atoms) is bonded to the carbon  atom on the a-position.  atom on the a-position, as disclosed in U.S. Pat. No. 6,949,  325, Japanese Unexamined Patent Application, First Publi› cation No. 2005-336452 or Japanese Unexamined Patent  Application, First Publication No. 2006-317803; and a poly- cycloolefin resin having a fluorinated alcohol, as disclosed in  Japanese Unexamined Patent Application, First Publication  No. 2006-259582. These resins are preferable in that a resist  pattern can be formed with minimal swelling. 