3D integration technology using hybrid wafer bonding and via-last TSV process

A three-layer-stacked wafer with CMOS devices was fabricated by using hybrid wafer bonding and backside-via-last TSV (7-μm diameter/25-μm length) processes. Successful fabrication of this wafer confirmed that copper/polymer hybrid wafer bonding brings seamless copper bonding in face-to-face (F2F) and back-to-face (B2F) configurations. The low capacitance of the TSVs results in the highest level of transmission performance (15 Tbps/W) so far. Additionally, according to ring-oscillator measurements, the keep-out-zone (KOZ) is up to 2 μm from a TSV. This extremely small KOZ is mainly attributed to low residual stress in the silicon surrounding a TSV.