TiN-Ti_xSi_y Codeposits A.P.C.V.D. Produced Using the TiCl₄-N₂-SiH₂Cl₂-H₂ System

Abstract
Mixtures of TiN_x, TiSi₂ and Ti₅Si₃(N) were chemically vapour codeposited at atmospheric pressure using the TiCl₄ - N₂ - SiH₂C1₂ - H₂ system. Compact materials with very intimately dispersed phases and with controlled composition were obtained between 825 - 875°C and using flow rate ranges : 0.5 ≤ D_N2 ≤ 2.5, and 0.05 ≤ D_SiH2Cl2 ≤ 0.2 (in l/h). D_TiCl4 and D_H2 were kept constant at 0.183 and 30 (in l/h) respectively. According to the Ti-Si-N ternary phase diagram, TiN_x whith x = 0.95 +/- 0.05, TiSi₂ and Ti₅Si₃(N), corresponding to some solubility of nitrogen into Ti₅Si₃, were in thermodynamical equilibrium. At 850°C, D_TiC14 = 0.183 and D_H2 = 30 (in l/h), the effect of N₂ and SiH₂Cl₂ input concentrations were studied. At D_SiH2Cl2 = 0.1 l/h, the deposition rate was found to increase linearly with the square root of the N₂ molar fraction up to 5.10^-2, then to decline at higher concentration. TiN_x was 20 mol% at D_N2 = 0.5 l/h, reached about 40 mol% at 1 l/h and remained almost constant while D_N2 increased to 2 l/h. At D_N2 = 2 l/h, about 70 mol% in TiN_x was obtained with D_SiH2Cl2 = 0.05 l/h. Then from D_SiH2Cl2 ranging from 0,l to 0.2 l/h, TiN_x concentration remains almost equal to 35 mol%. A linear dependence in the SiH₂Cl₂ concentration was observed for the growth rate. The relationship between the logarithmic plot of the growth rate versus the reciprocal of codeposition temperature (in Kelvin) was linear and an apparent activation energy of 105 kJ/mol was calculated. The effect of temperature on the TiN_x preferred orientations was also evidenced.