Dopant effects on lateral silicide growth in self-aligned titanium silicide process

The effects of sidewall material and implanted dopants have been investigated on the lateral silicide growth in self-aligned titanium silicide process. The SiO2 sidewall spacer showed no lateral silicide growth and has a low leakage current between gate and source/drain up to silicidation temperatures of 750 degrees C. This was found to be due to released oxygen from the SiO2 sidewall spacer into titanium film, which impedes silicon diffusion over the SiO2. However, the Si3N4 side-wall spacer showed dopant dependence of the lateral silicide growth and leakage current. This discrepancy between SiO2 and Si3N4 results from the fact that nitrogen has lower reactivity with titanium and less suppression of the lateral silicide growth than oxygen. The lateral silicide growth and leakage current in Si3N4 decreased in the order of dopant species of B > BF2 > As and P. Released dopants from Si3N4 can affect the silicon diffusion, and this is closely related to the reactivity of each dopant with titanium.