Crystalline defects in InP-to-silicon direct wafer bonding

InP-to-Si wafer bonding has been proposed as a way of circumventing the pro blems associated with lattice-mismatch in heteroepitaxial growth. Therefore , in this study the dislocation density and material degradation in InP-to- Si hydrophobic bonding are evaluated. Both interface and InP bulk defects w ere studied using IR-transmission. atomic force microscopy (AFM) and defect -etching. When the bonded wafers were annealed below 300 degreesC, no volum e dislocations were generated in InP. However, when annealing above 300 deg reesC. the thermal mismatch stress induced large numbers of volume dislocat ions in InP. It was also shown that hydrophobic InP-to-Si wafer bonding unf ortunately requires high-temperature annealing to achieve sufficient bondin g-strength. However, a considerably lower dislocation density was observed in InP-to-Si wafer bonding than that in InP heteroepitaxial growth on Si. A lso. when the samples were annealed above 400 degreesC. asymmetric voids em erged at the inter-face. These voids are associated with the nucleation of indium droplets which causes microcavities at the interface where volume di slocations can sweep-out, forming surface steps. The voids completely disap peared when channel-patterned interfaces were used.