Low-temperature direct flip-chip bonding for integrated micro-systems

This paper reports the results of low-temperature flip-chip bonding of a vertical cavity surface emitting laser (YCSEL) on a micromachined Si substrate. Low temperature bonding was achieved by introducing surface activation by plasma irradiation into the flip-chip bonding process. After the surfaces of the Au electrodes of the VCSEL and Si substrate were cleaned using an Ar radio frequency (RF) plasma, Au-Au bonding was carried out only by contact in ambient air. At a bonding temperature of 100 °C, the die-shear strength exceeded the failure criteria of MIL-STD-883.