Modified hydrogenated polysiloxazane, composition comprising same for forming silica-based insulation layer, method for preparing composition for forming silica-based insulation layer, silica-based insulation layer, and method for preparing silica-based insulation layer

Provided is modified hydrogenated polysiloxazane prepared by reacting hydrogenated polysiloxazane with a silane compound selected from a group consisting of polysilane, polycyclosilane, and silane oligomer. The modified hydrogenated polysiloxazane is configured such that the mole ratio of nitrogen atom to silicon atom is small, and therefore, the modified hydrogenated polysiloxazane can be applied to a composition for forming a silica-based insulation layer so as to significantly reduce film shrinkage when the silica-based insulation layer is formed.