Study of the rapid thermal nitridation and silicidation of Ti using elastic recoil detection. I. Ti on Si

This paper describes a study of the rapid thermal processing of Ti thin films on Si in Ar and N2 in the temperature range 400–1100 °C. The resulting layer structures were analyzed by means of Rutherford backscattering spectrometry and elastic recoil detection. The latter technique yields quantitative information with a low detection limit about the depth distribution of O and N. Rapid thermal annealing in both Ar and N2 results in the uptake of nitrogen in the Ti surface region. Very little oxygen, if any, is incorporated. This nitridation leads to a shift of the originally present oxygen from the surface region into deeper layers, notably at the higher temperatures. For rapid thermal processing (RTP) in both Ar and N2 the evolution of the layer structures is governed by a competition between silicide (TiSi2) formation at the interface and nitridation at the outer surface. For the case of RTP in N2, the nitride to silicide thickness ratio is considerably larger than for RTP in Ar. The originally present oxygen is found between the silicide and the Ti nitride. In the case of RTP in Ar, Si appears at the surface at temperatures above 600 °C via diffusion through a thin titanium (oxy) nitride layer. This results in a buried titanium nitride layer via lateral overgrowth of Si on a nanoscale. This silicon surface layer effectively stops further nitridation.