Patent ID: 8475693

Claim:
A method for fabricating a composite semiconductor structure, the method comprising: providing an initial composite structure comprising at least one intermediate layer interposed between a substrate and a superstrate, the substrate and a superstrate comprising the same or different semiconductor materials, and the intermediate layer comprising a CVD-deposited glass material having a composition whereby, when subjected to a suitable heat treatment, the material undergoes a structural transformation becoming spongy; and applying a suitable heat treatment to the initial composite structure at a temperature in the range from 900° C. to 1200° C. so that the as-deposited intermediate layer becomes spongy consequent to the structural transformation, wherein the glass material comprises silicon oxide doped with phosphorous or silicon oxide doped with phosphorous and boron, and wherein the spongy transformation comprises the formation of microbubbles or microcavities containing a gaseous phase.