Method for processing semiconductor substrate

The purpose of the present invention is to provide a method for processing a semiconductor substrate that can promote miniaturization of a pattern, and that can reduce damage to a substrate in a rework process. The present invention is a method for processing a semiconductor substrate, comprising: a step for coating directly or indirectly on a substrate a composition for forming a silicon-containing film that contains polycarbosilane and a solvent; a step for performing on the silicon-containing film formed by the step for coating the composition for forming a silicon-containing film at least one type of process selected from a group comprising radiation exposure, reactive gas exposure, plasma exposure, ion exposure, contact with a reactive liquid, and heating of 400 DEG C or greater; and a step for removing the silicon-containing film after the processing step using a removing liquid containing an acid or a removing liquid containing a base. It is preferable that the polycarbosilane have a structural unit re