SELECTIVE DEPOSITION OF TISI2 FROM H2-TICL4 GAS-MIXTURES AND SI - ASPECTS OF THERMODYNAMICS INCLUDING CRITICAL-EVALUATION OF THERMOCHEMICAL DATA IN THE TI-SI SYSTEM

Chemical vapor deposition (CVD) of TiSi2 from TiCl4, H-2, and substrate silicon has been investigated thermodynamically. From a critical evaluation of the thermochemical data, an assessment of the Ti-Si binary phase diagram has been performed. This is the basis of a new set of thermodynamic values for the titanium silicides, which have been used in the calculations. As a comparison, two other common data sets have also been used. The results from the calculations showed that the trends in selectivity as well as substrate etching were not affected by the choice of the silicide data. However, in the calculated CVD phase diagrams the stability regions for the various equilibria were strongly affected. The selectivity of the process was found to be very high and was favored by a low temperature and a low H-2/TiCl4, molar ratio. Moreover, improved selectivity can be expected for hot-wall reactor conditions. It was also shown that thermodynamics can be used for prediction of trends in substrate etching. The lowest etching yield was obtained at low pressures, at high temperatures, and at high H-2/TiCl4 molar ratios.