Fluorine-containing polymer, purification method, and radiation-sensitive resin composition

A radiation-sensitive resin composition, comprising:

• a fluorine-containing polymer including a repeating unit of formula (1) and a repeating unit of formula (2);
• and
• an acid-unstable resin including a repeating unit of the formula (2),
• wherein the formula (1) is
• where R1 represents a hydrogen atom, a methyl group or a trifluoromethyl group,
• A represents a single bond, an oxygen atom, a sulfur atom, a carbonyloxy group, an oxycarbonyl group, an amide group, a sulfonylamide group, or a urethane group, and
• R2 represents a linear or branched, partially or fully fluorinated alkyl group having 1 to 6 carbon atoms or a monovalent partially or fully fluorinated alicyclic hydrocarbon group having 4 to 20 carbon atoms,
• the formula (2) is
• where R3 represents a hydrogen atom, a methyl group or a trifluoromethyl group, and
• each R4 individually represents a monovalent alicyclic hydrocarbon group having 4 to 20 carbon atoms or a derivative thereof, or a linear or branched alkyl group having 1 to 4 carbon atoms, and
• at least one of the fluorine-containing polymer and the acid-unstable resin includes the repeating unit of the formula (2) satisfying that two of R4s taken together represent an alicyclic hydrocarbon group derived from cyclopentane or cyclohexane, together with the carbon atom to which the two of R4s bond.