HOW TO FABRICATE LOW-RESISTANCE METAL-DIAMOND CONTACTS

Three types of mesa etched contact resistance test structures with Al/ Si, Ti-Au, TiWN-Au contacts are compared. The contact resistivity was calculated using transmission-line model(TLM) theory which is fully ap plicable to diamond. For Al/Si contacts the lowest contact resistivity was obtained after annealing at 500 degrees C in dry nitrogen. The lo west contact resistivity for as-deposited contacts was found for Ti-Au . In general, the contact resistivity drops with increasing levels of B dopant and depends on the metallization scheme. The dependence of th e contact resistivity on the surface concentration of B for as-deposit ed Al/Si contacts can be fitted by a power-law indicative of spatial i nhomogenous areas in the contact region leading to an additional sprea ding resistance component. The contact resistivity depends exponention ally on the operating temperature for as-deposited Al/Si contacts but the thermal coefficient is independent of the doping level for heavily B-doped diamond films, which is typical for tunneling.