US Patent 9576827 Apparatus and method for wafer level bonding

A system for and a method of bonding a first wafer to a second wafer are provided. A second wafer chuck has a second surface, a profile of the second surface being adjustable by a profile control layer. The first wafer is placed on a first surface of a first wafer chuck, and the second wafer is placed on the second surface of the second wafer chuck. The first wafer and the second wafer are warped prior to bonding to form a first warped wafer and a second warped wafer, respectively. The first warped wafer is bonded to the second warped wafer.