Patent ID: 8790990

Claim:
A method for forming air gaps comprising: applying by a spin coating method a silica-based film forming material on a semiconductor substrate having recessed parts, the film forming material consisting of as separate components: (a) a siloxane polymer prepared by subjecting a first silane compound to hydrolytic condensation; (b) an alkanolamine in an amount of 0.01% to 10% by mass; (c) an organic solvent; (d) optionally water; (e) optionally an acid; and (f) optionally a second silane compound wherein the first silane compound is represented by the following general formula: R 1 n Si(OR 2 ) 4-n wherein R 1 represents a hydrogen atom or an alkyl group or an aryl group having 1 to 20 carbon atoms, R 2 represents a monovalent organic group, and n represents an integer of no less than 0 and no greater than 2; and baking the coated semiconductor substrate to form a silica-based film thereon, thereby covering the recessed parts to form the air gaps; wherein the alkanolamines are contained in the silica-based film forming material; and wherein a cross-linking reaction of the siloxane polymer progresses immediately after coating, and the liquidity of the silica-based film forming material declines prior to filling the recessed parts.