Separating bonded wafers. A bonded wafer pair is mounted between first and second bonding chucks having flat chuck faces, the first bonding chuck face including adjustable zones capable of movement relative to each other, at least a component of the relative movement is along an axis that is perpendicular to the flat first bonding chuck face. The adjustable zones of the first face are moved relative to each other in a coordinated manner such that a widening gap is formed between the bonding faces of the wafer pair.