Thermodynamic and experimental study of CVD of non-stoichiometric titanium nitride from TiCl₄N₂-H₂ mixtures

Abstract

Using the polynomial description of the Gibbs free energy of formation of titanium nitride against its composition, thermodynamic deposition diagrams were determined at 1900 K. The description of the whole range of non-stoichiometry needs XTiCl₄ < 10⁻² andXN₂ as low as 10⁻⁴. Deposition rates and composition of the film were studied. The cold wall reactor is associated with a dew point evaporator. At 1900 K, on a molybdenum substrate, experiments carried out as a function of input nitrogen, temperature and pressure, confirmed the theoretical trends. The different deposition mechanisms in relation to total pressure are thermodynamically related with a progressive reduction of the halide to solid titanium under one atmosphere instead of a major formation of gaseous titanium under 6.6 × 10⁻³ atm. The lowest N/Ti value obtained in the deposits is 0.63.