Positive resist composition and base material carrying layer of the positive resist composition

Abstract

A positive resist composition includes (A) an alkali-soluble polysiloxane resin, (B) an acid generator composed of a compound which generates an acid upon irradiation of active light or radiant ray, and (C) a compound in which at least one hydrogen atom of phenolic hydroxyl group or carboxyl group is substituted with an acid-decomposable group. This positive resist composition is useful for processes using F 2 excimer laser (157 nm), extreme-ultraviolet rays (EUV, vacuum ultraviolet rays; 13 nm) and other light sources having wavelengths equal to or shorter than that of KrF excimer laser, and has high definition and can form resist patterns with good sectional shapes. A base material carrying a layer of the positive resist composition is also useful.

What is claimed is:  
     
         1 . A polysiloxane resin comprising (a1) a siloxane unit containing an alkali-soluble group, and (a2) an arylsilsesquioxane unit containing an alkali-insoluble group, said alkali-insoluble group having no acid-decomposable group.  
     
     
         2 . A polysiloxane resin according to  claim 1 , wherein the alkali-soluble group of said siloxane unit (a1) is at least one of hydroxyl group and carboxyl group.  
     
     
         3 . A polysiloxane resing according to  claim 2 , wherein, in said siloxane unit (a1), the alkali-soluble group is bonded to the silicon atom of a siloxane group through at least one group selected from the group consisting of alkylene groups, cycloalkylene groups and aralkylene groups.  
     
     
         4 . A polysiloxane resin according to  claim 3 , wherein said siloxane unit (a1) is a hydroxybenzylsilsesquinoxane unit.  
     
     
         5 . A polysiloxane resin according to  claim 1 , wherein said siloxane unit (a2) is a phenylsilsesquioxane unit.  
     
     
         6 . A polysiloxane resin according to  claim 1 , wherein a molar ratio of the unit (a1) to the unit (a2) is from 1:9 to 9:1.  
     
     
         7 . A polysiloxane resin according to  claim 1 , wherein the resin has a weight average molecular weight of from 1000 to 100000.