THERMODYNAMICS OF THE FORMATION OF TIN FROM TICL4-NH3-H-2 ON A PATTERNED OXIDIZED SILICON SUBSTRATE

A thermodynamic study of titanium nitride formation on a patterned oxi dized silicon substate in the TiCl4-NH3-H-2 gaseous phase was carried out. Calculations were performed in the temperature range of 700-1300 K and in the total pressure range of 27-133 Pa. On a silicon oxide sur face, TiN formation occurs according to a three-step mechanism involvi ng TiCl3 formation as an intermediate compound. On a TiN surface, the deposition occurs in the same manner. On a silicon surface, titanium d isilicide or silicon nitride are the only condensed phases obtained at equilibrium in the TiCl4-rich and NH3-rich cases, respectively. Becau se silicon diffusion is allowed through TiSi2 and not through Si3N4, T iN can only grow on a Si3N4 surface. In spite of the fact that Si3N4 i s not conductive, the formation of a thin Si3N4 covering layer is nece ssary for TiN growth. Calculations show that the best TiN yield is obt ained with an ammonia-rich gaseous phase at a deposition temperature o f about 1100 K.