Methods for hybrid wafer bonding

A method of bonding semiconductor wafers, comprising:

• forming a metal pad layer in a dielectric layer on at least two semiconductor wafers;
• performing a CMP process on each of the at least two semiconductor wafers to expose the metal pad layer and planarize the dielectric layer to form a bonding face on each of the at least two semiconductor wafers;
• performing an oxidation process on each of the at least two semiconductor wafers to form a metal oxide in the metal pad layers;
• performing an oxide etch process on each of the at least two semiconductor wafers to remove the metal oxide, exposing a recessed surface of each of the metal pad layers;
• determining that the recessed surface of each of the metal pad layers meets a profile match criterion;
• responsive to the determining, aligning the bonding faces on the at least two semiconductor wafers in a face to face relation;
• physically contacting the bonding faces of the at least two semiconductor wafers;
• and
• subsequently annealing the at least two semiconductor wafers;
• wherein bonding occurs between the dielectric layers and between the metal pad layers of the at least two semiconductor wafers.

A method of wafer bonding, comprising:

• forming a copper pad layer in a dielectric layer on at least two semiconductor wafers;
• performing a CMP process on the dielectric layer on each of the at least two semiconductor wafers to expose the copper pad layer and planarize the dielectric layer to form a bonding face on each of the at least two semiconductor wafers;
• performing an oxidation process on each of the at least two semiconductor wafers to form a copper oxide to a predetermined depth in the copper pad layers;
• performing an oxide etch process on each of the at least two semiconductor wafers to remove the copper oxide, exposing a recessed planar surface of each of the copper pad layers;
• aligning the bonding faces on the at least two semiconductor wafers in a face to face relation;
• physically contacting the bonding faces of the at least two semiconductor wafers;
• and
• thermally annealing the at least two semiconductor wafers;
• wherein bonding occurs between the dielectric layers and between the copper pad layers of the at least two semiconductor wafers.