Ion-implanted TiN films as diffusion barriers in silicon device technology

Abstract

Titanium nitride (TiN) films are of increasing interest for metallization schemes in silicon devices, particularly for very-large-scale integration applications, as they act as diffusion barriers between the silicon substrate and the top metal layer. Polycrystalline TiN films of various thicknesses were obtained by implanting N 2 + ions in titanium-coated silicon wafers. The sheet resistance of these films is already low in the as-implanted form and tends to undergo a further marked decrease after heat treatments carried out between 600 and 800°C in vacuum; this is related in some cases to the formation on annealing of a film of titanium silicide at the TiN-Si interface. The deposition of an aluminium layer 1 μm thick onto the TiN barrier followed by thermal treatment in a furnace at 600°C for 10 min gives rise to negligible diffusion of silicon in aluminium, thus demonstrating the stability of these TiN films as diffusion barriers.