Materials suitable for shallow trench isolation

A method of forming isolation structures in a semiconductor substrate comprising:

• a) etching trenches in a semiconductor substrate, thereby forming substantially unetched areas of said substrate between said trenches;
• b) depositing a conformal fill composition that substantially fills said trenches and to form a film, said composition comprising a silicon containing pre-polymer, optionally water, and optionally a metal-ion-free catalyst selected from the group consisting of onium compounds and nucleophiles;
• (c) crosslinking the composition to produce a gelled film, and
• (d) heating the gelled film at a temperature of from about 750° C. to about 1000° C. and for a duration effective to remove substantially all organic moieties and to produce a substantially crack-free, and substantially void-free silica dielectric film.
• e) optionally planarizing said silica dielectric film.