Hybrid bond using a copper alloy for yield improvement

A method for bonding a pair of semiconductor structures together, the method comprising:

• providing a pair of semiconductor structures comprising dielectric layers and metal features arranged in the dielectric layers, wherein the metal features comprise a primary metal that is pure, and wherein at least one of the metal features is a metal alloy, comprising the primary metal and a secondary metal;
• and
• forming a hybrid bond interface between the semiconductor structures, wherein the forming the hybrid bond interface comprises forming a first bond interface between the dielectric layers, and further forming a second bond interface between the metal features, and wherein the second bond interface is formed with the secondary metal filling voids between metal grains of the metal features;
• wherein the providing the pair of semiconductor structures comprises:
• performing an etch into a first dielectric layer of the dielectric layers to form an opening for a first metal feature of the metal features;
• forming a seed layer of the metal alloy lining the opening;
• forming a fill layer of the primary metal filling the opening over the seed layer;
• performing an anneal of the seed and fill layers to interdiffuse the seed and fill layers, such that the fill layer becomes the metal alloy;
• and
• performing a chemical mechanical polish (CMP) into the interdiffused seed and fill layers to form the first metal feature.

A method for bonding a pair of integrated circuits (ICs) together, the method comprising:

• providing a first IC and a second IC, wherein the first and second ICs comprise individual back-end-of-line (BEOL) interconnect structures overlying individual semiconductor substrates;
• forming a first metal feature and a second metal feature respectively in the BEOL interconnect structures of the first and second ICs, wherein the first metal feature is copper alloy, wherein the second metal feature is pure copper, and wherein the copper alloy comprises a primary metal of copper and a secondary metal different than copper;
• hybrid bonding the first and second ICs together through the BEOL interconnect structures, wherein the hybrid bonding the first and second ICs together comprises bonding dielectric layers individual to the first and second ICs together, and further bonding the first and second metal features together, and wherein the bonding the first and second metal features together results in voids between the first and second metal features;
• and
• performing an anneal to the first and second ICs to form precipitates of the secondary metal from the copper alloy, wherein the precipitates are formed filling the voids between the first and second metal features.