Low temperature direct bonding of flip-chip mounting VCSEL to Si substrate

This paper describes the result of low temperature direct metal bonding of vertical-cavity surface-emitting laser (VCSEL) for flip-chip mounting to Si substrate by surface activated bonding (SAB) method. In the SAB process, radio frequency (RF) driven, low-pressure argon (Ar) plasma was used to clean the surfaces to be bonded. After organic contaminants on the surfaces of Au electrodes of the VCSEL and Si substrate were removed by Ar RF plasma, Au-Au direct bonding was carried out in the ambient air. The high die-shear strength of 84 MPa (77.4 gf) was achieved at a bonding temperature of 150degC. Therefore, Au SAB bonding in the ambient air can be applied to realize low cost and highly functional optical microsystems