PHASE IDENTIFICATION OF MICRO AND MACRO BUBBLES AT THE INTERFACE OF DIRECTLY BONDED GAAS ON SAPPHIRE

Direct wafer bonding (DWB) of 3 '' GaAs and R-cut sapphire was perform ed in a microcleanroom using ultra pure water as cleaning agent. The i nitial bonding is mediated by Van der Waals forces and hydrogen bridge s. The bond energy is released by subsequent heating up to temperature s of 500 degrees C. During heating the formation of macroscopic bubble s at the interface was observed. Details of the interface structure we re investigated by cross-sectional as well as plan-view transmission e lectron microscope (TEM) micrographs. The chemical composition of the elements at the interface was measured by energy dispersive X-ray anal ysis (EDX) and electron energy loss spectroscopy (EELS). A high densit y of micro bubbles in bonded areas, a network of micro channels in the transition region and macro bubbles in debonded areas could be distin guished. The macro bubbles are filled with a porous oxide. X-ray diffr action (XRD) and selected area electron diffraction (SAED) revealed th e growth of textured gamma-Ga2O3 and elemental arsenic. (C) 1998 Chapm an & Hall.