Oxides formation on hydrophilic bonding interface in plasma-assisted InP/Al2O3/SOI direct wafer bonding

Successful direct wafer bonding between InP and silicon-on-insulator (SOI) wafers has been demonstrated by adopting a 20-nm-thick Al2O3 as the intermediate layer. A detailed investigation on the property of the bonding interface is carried out. Water contact angle test reveals an improved hydrophilicity for both the InP and the Al2O3/SOI wafers after oxygen plasma surface activation. X-ray photoelectron spectroscopy is employed to characterize the bonding interface before and after the wafer bonding process. It is found that oxides are formed on the bonding interface during bonding, which helps ensure high quality hydrophilic bonding.