A positive resist composition and method for forming a resist pattern are provided which enable a resist pattern with excellent shape to be obtained. The resist composition includes a resin component (A) which exhibits increased alkali solubility under action of acid, an acid-generator component (B) which generates acid upon irradiation and an organic solvent (S) in which the components (A) and (B) are dissolved, the resin component (A) including a copolymer (A1) containing: a structural unit (a1) having an acetal-type protected group, a structural unit (a2) derived from an acrylate ester having a lactone-containing polycyclic group, which is represented by general formula (a2-1) shown below; and a structural unit (a3) derived from an acrylate ester having a polar group-containing aliphatic hydrocarbon group:
wherein R represents a hydrogen atom, a fluorine atom, a lower alkyl group or a fluorinated lower alkyl group; R′ represents a hydrogen atom, a lower alkyl group or an alkoxy group of 1 to 5 carbon atoms; and m represents 0 or 1.
提供了一种正性光阻组合物和形成光阻图案的方法,可以获得具有优异形状的光阻图案。该光阻组合物包括
树脂成分(A),在酸的作用下具有增加的碱溶性,酸发生剂成分(B),在辐照下生成酸,以及有机溶剂(S),其中成分(A)和(B)被溶解,
树脂成分(A)包括一个共聚物(A1),该共聚物包含:具有
缩醛型保护基的结构单元(a1),由含有内酯基多环群的
丙烯酸酯衍生的结构单元(a2),其由下式表示:(a2-1);以及由含有极性基团的脂肪族碳氢基团的
丙烯酸酯衍生的结构单元(a3):其中R表示氢原子、
氟原子、低碳基或
氟化低碳基;R'表示氢原子、低碳基或1至5个碳原子的烷氧基;m表示0或1。