Impact of Cu Protrusion on Connection Resistance in Hybrid Bonding of Via-middle TSV Wafer

In this study, we investigated the impact of Cu protrusion on the connection resistance as detailed data regarding the hybrid bonding of the via-middle through-silicon-via (TSV) wafer. After several Cu TSV wafers and Cu electrode wafers with different amounts of Cu protrusion were prepared and bonded via a surface-activated bonding method using ultrathin Si films, the connection resistance of bonded wafers (that is, the sum of the TSV, Cu electrode, and interface resistances) was evaluated via four-terminal measurements. The results demonstrate that the amount of Cu protrusion is a crucial parameter for the hybrid bonding of via-middle TSV wafers with ultrathin Si films, and an electrical connection between the TSV and Cu electrode can be achieved without heat treatment by adjusting the Cu protrusion.