Observation of microstructure at the polycrystalline silicon and tungsten silicide interface

Abstract

Formation of native oxide on the WSi 2 surface during loading into the LPCVD reactor of poly-silicon, and annihilation of the oxide at the interface between poly-silicon and WSi 2 with subsequent annealing are studied using microstructural analysis. The WSi 2 surfaces are covered with native oxide composed of WO 3 and SiO 2 which were formed in the LPCVD reactor during loading. From XTEM observation, the poly-silicon/WSi 2 interface is completely covered with an amorphous bilayer film. The bilayer is concluded to be WO 3 in the upper layer and SiO 2 in the lower layer. The two-layer structure persists during subsequent annealing up to 900°C. In the sample annealed at 1020°C, the oxide layers are annihilated but partially remain at the region surrounded by poly-Si and two granular WSi 2 grains.