Wafer processing method and apparatus

A system for bonding wafers comprising:

• a first surface of a first wafer chuck, wherein the first surface is one of silicon oxide, silicon nitride, glass, or aluminum oxide and the first surface having a convex first curvature greater than zero and being curved prior to both an application of a first vacuum to the first wafer chuck and an attachment of a plurality of dies within a first wafer;
• vacuum openings extending through the first curvature of the first surface;
• a second surface of a second wafer chuck movable relative to the first surface of the first wafer chuck, the second surface having a convex static second curvature less than the first curvature and greater than zero, having a deformation of less than 2 μm, and wherein the second surface is curved prior to both an application of a second vacuum to the second wafer chuck and an attachment of a second wafer;
• and
• vacuum openings extending through the second curvature of the second surface.

A system for bonding wafers comprising:

• a first surface of a first wafer chuck, the first surface being curved prior to both an application of a first vacuum to the first wafer chuck and an attachment of a plurality of dies within a first wafer, wherein the first surface is glass and wherein the first surface has a first convex curvature and a deformation of less than 2 μm from a center of the first surface to an edge of the first surface;
• a second surface of a second wafer chuck movable relative to the first surface of the first wafer chuck, the second surface having a second convex curvature, wherein the second surface is curved prior to both an application of a second vacuum to the second wafer chuck and an attachment of a second wafer, the first convex curvature being smaller than the second convex curvature;
• and
• an alignment unit located to emit infrared energy through the first surface.