Fluorine-containing phenylmaleimide derivative, polymer, chemically amplified resist composition, and method for pattern formation using the composition

A polymer characterized by being obtained by polymerizing monomers containing a fluorine-containing phenylmaleimide derivative represented by the following formula (1a):

• wherein one of R1, R2, R3, R4 and R5 is a hydroxy group, an alkoxyl group, or an acid-dissociable organic group of 20 or less carbon atoms capable of generating a hydroxy group when decomposed by an acid;
• at least two of the remainder are each a fluorine atom;
• and when there is still a remainder, it is a hydrogen atom.

A polymer characterized by containing at least a structural unit represented by the general formula (2) and having a weight-average molecular weight of 2,000 to 200,000

• wherein in formula (2) one of R1, R2, R3, R4 and R5 is a hydroxy group, an alkoxyl group, or an acid-dissociable organic group of 20 or less carbon atoms capable of generating a hydroxy group when decomposed by an acid;
• at least two of the remainder are each a fluorine atom;
• and when there is still a remainder, it is a hydrogen atom.