Patent ID: 8455356

Claim:
A method of forming a through hole extending through a first wafer and a second wafer bonded to the first wafer, the first wafer having a face and metallic features exposed at the face, the second wafer having a face confronting the face of the first wafer and metallic features exposed thereat and joined with the metallic features of the first wafer, the method comprising: a) etching a hole extending through the first wafer until the face of the second wafer is partially exposed, the hole having a first wall extending in a vertical direction, the hole having a second wall sloping inwardly away from the first wall to an inner opening through which the face of the second wafer is exposed; b) directing particles into the hole to sputter material of at least one of the first and second wafers, the sputtered material being deposited onto at least one of the exposed confronting faces of the first and second wafers adjacent to the hole; and c) resuming etching the hole so as to extend the first wall fully through the first wafer, the interfacial gap and into the second wafer, such that the wall of the hole extends continuously from the first wafer through the sputtered material and into the second wafer.