Patent attributes
A wafer bonding process that compensates for curvatures in wafer surfaces, and a wafer stack produced by the bonding process. The process entails forming a groove in a surface of a first wafer, depositing a bonding stack on a surface of a second wafer, aligning and mating the first and second wafers so that the bonding stack on the second wafer contacts a bonding site on the first wafer, and then heating the first and second wafers to reflow the bonding stack. The groove either surrounds the bonding site or lies entirely within the bonding site, and the heating step forms a molten bonding material, causes at least a portion of the molten bonding material to flow into the groove, and forms a bonding structure that bonds the second wafer to the first wafer. Bonding stacks having different lateral surface areas can be deposited to form bonding structures of different heights to compensate for variations in the wafer gap.
