COMPOSITION FOR FORMING SILICON-CONTAINING RESIST UNDERLAYER FILM AND PATTERNING PROCESS

The present invention is a composition for forming a silicon-containing resist underlayer film, containing a condensation reaction-type thermosetting silicon-containing material (Sx), being a polysiloxane resin, where the material has a non-condensation reactive organic group that reacts with a radical chemical species, the resin includes more than 0 and 70 mol% or less of one or more of a repeating unit represented by the following general formula (Sx-4) and a repeating unit represented by the general formula (Sx-5), and the organic group remains unreacted after a heat-curing reaction of the polysiloxane resin. This provides: a composition for forming a resist underlayer film containing a thermosetting silicon-containing material in photolithography using a high-energy beam, the material improving sensitivity, LWR, and resolution of an upper layer resist and further contributing to the prevention of pattern collapse; and a patterning process using the composition for forming a resist underlayer film.