Materials aspects of Ti and Co silicidation of narrow polysilicon lines

The scalability of Ti and Co self-aligned silicide processes to deep-submicrometer technologies is determined by the fundamental materials aspects controlling phase formation and evolution. The kinetics of the high resistivity phase to low resistivity phase transformation (TiSi2 C49 to C54 transformation for Ti, and CoSi to CoSi2 transformation for Co) were studied for films on deep-submicrometer n(+) gates. For TiSi2, results of a detailed Johnson-Mehl-Avrami analysis show that activation energies for the transformation increase with decreasing him thickness in the 28-64 nm range and are insensitive to linewidth in the 0.26-0.8 mu m range, while transformation times increase as the linewidth or film thickness decreases. For Co, the transformation is diffusion limited, with the square of CoSi2 film thickness depending linearly on time. The transformation rate is also observed to be linewidth dependent, while the activation energy is quite insensitive to linewidth. The Co silicide phase transformation proceeds faster than the Ti silicide phase transformation at low temperatures, resulting in a range of process parameters for which no linewidth dependence is observed for Co silicide and a strong linewidth dependence is observed for Ti silicide owing to incomplete phase transformation of the narrowest lines.