Effect of the oxidation of TiN on the stability of the Al/TiN interface

The stability of TiN barriers deposited between Si or SiO2 substrates and AlSiCu metallic alloy contacts was investigated as a function of the sintering temperature and of the application of an oxidation step to the barrier. It was found that Al penetrates the barrier during the sintering at 450 °C for 1 h, which also results in the diffusion of Ti inside the Al alloy. This mutual interdiffusion increases with temperature but when oxygen is present at the barrier surface, the intensity of diffusion processes decreases considerably. It is also established that the barrier remains more stable on SiO2 than on the Si substrate. It is suggested that the better reaction resistance of oxidized TiN compared with oxygen-free nitride may be due to the blocking of fast-diffusion paths of Al diffusion by oxygen and subsequently the formation of Al2O3, AlN, and TiAl3 phases during sintering.