INTERFACE MICROSTRUCTURE OF TITANIUM THIN-FILM SILICON SINGLE-CRYSTAL SUBSTRATE CORRELATED WITH ELECTRICAL BARRIER HEIGHTS

The titanium (Ti)/single-crystal silicon (Si) interface has been examined by cross-section high-resolution transmission electron microscopy (HRTEM) combined for the first time with 2-nm-diam probe, energy-dispersive spectrometry. HRTEM shows that thin Ti-Si alloy formation always occurs at the interfaces, even in the as-deposited state. The thickness of the reacted alloy depends on the crystallinity of the Si surface, but does not depend on impurities or doping level. Crystallization of the Ti-Si alloy depends on the annealing temperature; it remains in the amorphous phase after annealing at temperatures lower than 430-degrees-C, and the C49 TiSi2 crystal phase was observed as the first crystalline phase after annealing at 460-625-degrees-C. The composition of the Ti-Si alloy at the Si interface is close to TiSi2, and it remains amorphous with variable composition across the alloy. It seems that the electrical barrier height is determined by the degree of crystallinity of TiSi2 at the Si interface. The barrier height for TiSi2/p-type Si interface decreases from 0.73 to 0.57 eV, accompanied by the crystallization of TiSi2 at around 460-degrees-C.