Patent ID: 7566631

Claim:
A method of bonding two wafers having a bonded surface area comprising: providing a first wafer having a substantially out-gassed oxide layer containing no surface hydroxyl groups, physisorbed water, or a combination thereof on a surface of said first wafer, said substantially out-gassed oxide layer is formed by oxidation followed by annealing, at a temperature T 1 , wherein T 1 is from about room temperature to about 300° C., providing a second wafer having a surface; polishing said surface of said second wafer and said substantially out-gassed oxide layer of said first wafer to provide polished surfaces having a root mean square surface roughness of less than about 0.5 nm; treating the polished substantially out-gassed oxide layer of the first wafer and the polished surface of the second wafer at room temperature with a solution containing NH 4 OH; contacting the treated surfaces with each other; and annealing the contacted wafers in an inert gas ambient and at a temperature T 2 which is less than or equal to T 1 and is within a range from about room temperature to about 300° C. thereby forming a bonded wafer pair which has a surface energy of about 2000 mJ/m 2 or greater and a bonded interface that has a dislocation density of less than 10 6 cm −2 and a void/bubble density of less than about 1% of the bonded surface area.