Patent ID: 7651829

Claim:
A method for preparing a polymer for a positive resist material, the polymer comprising at least one monomer unit selected from a group consisting of a monomer unit (A), a monomer unit (B) and a monomer unit (C) represented by the following formula (1): wherein R 1 represents a hydrogen atom, an alkyl group or an acyl group; R 2 and R 3 each independently represents a hydrogen atom, a fluorine atom, a C 1-4 alkyl group or a C 1-4 alkyl group having at least one fluorine atom; R 5 represents a halogen atom, an alkyl group, an oxoalkyl group, an acyl group, an acyloxy group, or an alkoxycarbonyl group; R 7 represents an acid-labile group; and R 4 , R 6 and R 8 each independently represents a linear, branched, cyclic or bridged cyclic C 3-20 alkylene group or a C 6-20 arylene group; and having a glass transition temperature (Tg) of 100° C. or greater; and the method comprising the steps of: preparing a polysilsesquioxane by hydrolysis and condensation at a temperature from 0 to 100° C. of a monomer or monomers corresponding to the selected monomer unit and being selected from monomers represented by the following formula (2): wherein X may be the same or different and each represents a C 1-10 alkyl group, an aryl group, a trifluoropropyl group, a hydroxyl group, a C 1-4 alkoxy group or a halogen atom and at least two of the three X groups in one compound are each a hydroxyl group, a C 1-4 alkoxy group or a halogen atom; and when chlorosilane is used, a hydroxyl group in an organic side chain is acetylated or pivaloylated so as to prevent a reaction between the chlorosilane and the hydroxyl group; dehydrating the obtained polysilsesquioxane; and maturing the dehydrated polysilsesquioxane under an anhydrous condition at a temperature from 80 to 200° C. in the presence of a basic catalyst so as to heighten a condensation degree of the polysilsesquioxane.