WAFER BONDING OF GALLIUM-ARSENIDE ON SAPPHIRE

Three-inch (100) gallium arsenide wafers were bonded to <(1(1)over bar 02)> sapphire in a micro-cleanroom at room temperature under hydrophi lic or hydrophobic surface conditions. Subsequent heating up to 500 de grees C increased the bond energy of the GaAs-on-sapphire (GOS) wafer pair close to the fracture energy of the bulk material. The bond energ y was measured as a function of the temperature. Since the thermal exp ansion coefficients of GaAs and sapphire are close to each other, the bonded wafer pair is stable against thermal treatment and quenching in liquid nitrogen. During heating in different gas atmospheres, macrosc opic interface bubbles and microscopic imperfections were formed withi n the bonding interface, which were analysed by transmission electron microscopy (TEM). These interface bubbles can be prevented by hydropho bic bonding in a hydrogen atmosphere.