Low-temperature LD direct bonding for highly functional optical MEMS

This paper reports the results of low-temperature flip-chip bonding of a vertical cavity surface emitting laser (VCSEL) 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 degC, the die-shear strength exceeded the failure criteria of MIL-STD-883