Patent ID: 7645486

Claim:
A method of manufacturing a composite substrate having a buried silicon dioxide layer which comprises: depositing a silicon dioxide layer on a source substrate by: depositing a layer of silicon dioxide upon the substrate using a low pressure chemical vapour deposition (LPCVD) process, wherein the layer is deposited employing simultaneously a flow of tetraethylorthosilicate (TEOS) as the source material for the film deposition and a flow of a diluent gas that is not reactive with TEOS, with the diluent gas and TEOS being present in the flow at a diluent gas/TEOS ratio of between about 0.5 and 100; and annealing the silicon dioxide layer at a temperature between about 600° C. and 1200° C., for a duration between about 10 minutes and 6 hours to reduce surface roughness compared to silicon dioxide layers provided from TEOS alone or at a different diluent gas/TEOS ratio; implanting atomic species within the source substrate to define therein a zone of weakness which demarcates a thin top layer from a remainder of the substrate, with the thin top layer being in contact with the silicon dioxide layer; directly bonding a support substrate to the silicon dioxide layer by molecular adhesion, detaching the remainder of the source substrate along the zone of weakness to obtain the composite substrate.