Bond chuck, methods of bonding, and tool including bond chuck

A tool comprising:

• a wafer bonding module comprising:
• a first chuck having a first surface and a second surface opposite the first surface, the first surface being configured to accept a first wafer, wherein the first surface comprises a plurality of convex regions, and wherein a first center of curvature of a first convex region of the plurality of convex regions is closer to the second surface than a second center of curvature of a second convex region of the plurality of convex regions;
• and
• a second chuck having a third surface, the third surface being configured to accept a second wafer to be bonded to the first wafer.

A tool comprising:

• a wafer bonding module comprising:
• a first chuck having a first surface, the first surface being configured to hold a first wafer, wherein the first surface comprises a plurality of concentric regions, wherein each of the plurality of concentric regions is a convex surface, and wherein a first curvature of a first concentric region of the plurality of concentric regions is greater than a second curvature of a second concentric region of the plurality of concentric regions;
• and
• a second chuck having a second surface, the second surface being a planar surface, the second surface being configured to hold a second wafer to be bonded to the first wafer.