Effects of variations of silicide characteristics on the Schottky-barrier height of silicide-silicon interfaces

Abstract

One basic question concerning Schottky-barrier formation at the silicide-Si interface is whether the barrier height is influenced by the material characteristics of the silicide. This question was investigated by studying the barrier formation at Pd-Si and Ni-Si interfaces over a range of parameters, including the silicide stoichimetry, microstructure, substrate orientation, surface preparation and annealing after silicide formation. The barrier was formed by evaporating metal on chemically cleaned and atomically cleaned [ultrahigh-vacuum- (UHV-) prepared] Si surfaces. The photoresponse technique was used to measure the barrier height and results are compared with $I\ensuremath{-}V$ measurements. Rutherford ion backscattering and transmission electron microscopy were used to characterize the silicide phase, microstructure, and interface morphology. Within the experimental accuracy, the barrier height was found to be unaffected by variations in the silicide characteristics with the exception of surface preparation. The results can be qualitatively understood by classifying the interface to be either extrinsic or intrinsic. The barrier height for the extrinsic interface is mainly controlled by defects and contaminants induced during the praparation of the interface. For the intrinsic interface it is determined by some interfacial characteristics originating from metal-silicon interaction at the interface. We proposed that one such characteristic is the metal-silicon bond at the interface.