Patent ID: 7736993

Claim:
A method of fabricating a composite substrate, which comprises: providing a first insulating layer on a support substrate at a thickness of e 1 and providing a second insulating layer on a source substrate at a thickness of e 2 , with each layer having an exposed face for bonding; providing plasma activation energy in an amount sufficient to activate one of a portion of the thickness of the face of the first insulating layer e mp1 or a portion of the thickness of the face of the second insulating layer e mp2 ; providing a final insulating layer by molecular bonding the face of the first insulating layer with the face of the second insulating layer; and removing a back portion of the source substrate while retaining an active layer comprising a remaining portion of the source substrate bonded to the support substrate with the final insulating layer interposed therein to form the composite substrate; wherein the thicknesses e 1 , e 2 of the first and second insulating layers are sufficient to provide the final insulating layer with a thickness of 50 nanometers or less, and the plasma activation energy and respective thicknesses e 1 , e 2 of the first and second insulating layers are selected such that only at least one of the respective thicknesses e mp1 and e mp2 of the faces of the first insulating layer and the second insulating layer is activated, and wherein the first and the second insulating layers have respective tunneling distances of d 1 and d 2 , and the following relationships are satisfied: e 1 ≧e mp1 +d 1 and e 2 ≧e mp2 +d 2 .