Hermetic Wafer Level Packaging

A method of packaging, comprising:

• providing a first wafer, wherein the first wafer contains a plurality of transistors and an interconnect structure having a plurality of metal layers;
• providing a second wafer, wherein the second wafer contains a through-silicon-via (TSV) and a bonding pad disposed on the TSV;
• and
• bonding, through a metal diffusion process, the bonding pad of the second wafer to a top-most metal layer of the interconnect structure of the first wafer.

A method of packaging, comprising:

• providing a first semiconductor wafer and a second semiconductor wafer;
• forming a first bonding pad on the first wafer, the first bonding pad including a first bonding material;
• forming a second bonding pad on the second wafer, the second bonding pad including a second material different from the first material, one of the first and second materials being aluminum, and the other thereof being a titanium alloy;
• and
• bonding the first and second wafers together through the first and second bonding pads.