Patent ID: 8865390

Claim:
A pattern forming process, comprising: applying a resist composition onto a substrate, the resist composition comprising a polymer comprising recurring units of acid labile group-substituted vinyl alcohol and maleic anhydride and/or maleimide, an acid generator, and an organic solvent, prebaking the composition to form a resist film, exposing the resist film to high-energy radiation, baking, and developing the exposed film in an organic solvent-based developer to form a negative pattern wherein the unexposed region of film is dissolved away and the exposed region of film is not dissolved, wherein the recurring units of acid labile group-substituted vinyl alcohol and maleic anhydride and/or maleimide are represented by the general formula (1): wherein R 1 is an acid labile group, wherein X is an oxygen atom or NR 2 , wherein R 2 is hydrogen, hydroxyl, or a straight, branched or cyclic C 1 -C 6 alkyl group which may contain one or two or more groups selected from the group consisting of hydroxyl, ether, ester, carbonyl, and acid-labile groups, wherein a1 and a2 are numbers in the range: 0<a1<1.0, 0<a2<1.0, and 0<a1+a2≦1.0, wherein said acid labile group is selected from groups of the formula (AL-10) and acetal groups of the formula (AL-11): wherein R 51 and R 54 each are a monovalent hydrocarbon group of 1 to 40 carbon atoms which may contain a heteroatom such as oxygen, sulfur, nitrogen or fluorine; wherein R 52 and R 53 each are hydrogen or a monovalent hydrocarbon group of 1 to 20 carbon atoms which may contain a heteroatom such as oxygen, sulfur, nitrogen or fluorine; wherein a5 is an integer of 0 to 10; and wherein a pair of R 52 and R 53 , R 52 and R 54 or R 53 and R 54 may bond together to form a ring with the carbon atom or the carbon and oxygen atoms to which they are attached, the ring having 3 to 20 carbon atoms.