Microstructure modulation for metal wafer-wafer bonding

A method of forming a three-dimensional (3D) bonded semiconductor structure, the method comprising:

• providing a first semiconductor structure comprising a first semiconductor wafer, a first interconnect structure, a first bonding oxide layer, and at least one first metallic bonding structure having a columnar grain microstructure and embedded in the first bonding oxide layer, and a second semiconductor structure comprising a second semiconductor wafer, a second interconnect structure, a second bonding oxide layer, and at least one second metallic bonding structure having a columnar grain microstructure and embedded in the second bonding oxide layer;
• and
• bonding the first semiconductor structure to the second semiconductor structure, wherein the bonding provides a bonding interface between the first and second bonding oxide layers and another bonding interface between the at least one first and second metallic bonding structures, wherein during the bonding columnar grain growth is initiated and provides at least one columnar grain that extends across the another bonding interface that is present between the first and second metallic bonding structures.