US Patent 9496239 Nitride-enriched oxide-to-oxide 3D wafer bonding

A semiconductor structure comprising a first semiconductor structure; a second semiconductor structure; and a silicon-nitride layer configured to bond the first semiconductor structure and second semiconductor structure together. The first semiconductor structure comprises a first wafer; a first dielectric layer; a first interconnect structure; and a first oxide layer. The second semiconductor structure comprises a second wafer; a second dielectric layer; a second interconnect structure; and a second oxide layer. The structure further comprises a first nitride layer residing on a top surface of the first oxide layer formed by a nitridation process of the top surface of the first oxide layer; and a second nitride layer residing on a top surface of the second oxide layer formed by the nitridation process of the top surface of the second oxide layer. Further, the silicon-nitride layer comprises the first nitride layer and the second nitride layer.