The role of Ni buffer layer on high yield low temperature hermetic wafer bonding using In/Sn/Cu metallization

Low temperature hermetic wafer bonding using In/Sn interlayer and Au/Ni/Cu metallization as the high-melting-point (HMP) components was reported, wherein the thin Ni layer was introduced as a buffer layer to prevent solder consumption after their deposition. 8 in. wafer to wafer bonding was achieved at 180 °C for 20 min under 5.5 Mpa. Voids free seal joints composed of high temperature intermetallic compounds were obtained with good hermeticity. Present results show that the buffer layer is the key to ensure high yield hermetic wafer bonding when the low-melting-point solder was deposited directly on the HMP component.