InP-to-Si wafer bonding was proposed as a way of circumventing the problems associated with lattice-mismatch in hetero-epitaxial growth. Therefore, the dislocation density and material degradation in InP-to-Si hydrophobic bonding were evaluated. Both interface and InP bulk defects were studied using IR-transmission, atomic force microscopy and defect-etching. When the bonded wafers were annealed below 300C, no volume dislocations were generated in InP. However, when annealing above 300C, the thermal mismatch stress induced large numbers of volume dislocations in InP. It was also shown that hydrophobic InP-to-Si wafer bonding unfortunately requires high-temperature annealing to achieve sufficient bonding-strength. However, a considerably lower dislocation density was observed in InP-to-Si wafer bonding than that in InP hetero-epitaxial growth on Si. Also, when the samples were annealed above 400C, asymmetric voids emerged at the interface. These voids were associated with the nucleation of In droplets which caused micro-cavities at the interface where volume dislocations could sweep-out, forming surface steps. The voids completely disappeared when channel-patterned interfaces were used.

Crystalline Defects in InP-to-Silicon Direct Wafer Bonding. D.Pasquariello, M.Camacho, F.Ericsson, K.Hjort: Japanese Journal of Applied Physics - 1, 2001, 40[8], 4837-44