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

Abstract

Mixtures of TiN x , TiSi 2 and Ti 5 Si 3 (N) were chemically vapour codeposited at atmospheric pressure using the TiCl 4 -N 2 -SiH 2 Cl 2 -H 2 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 with x = 0.95 ± 0.05, TiSi 2 and Ti 5 Si 3 (N), corresponding to some solubility of nitrogen into Ti 5 Si 3 , were in thermodynamical equilibrium. At 850°C, D TiC14 = 0.183 and D H2 = 30 (in l/h), the effect of N 2 and SiH 2 Cl 2 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 N 2 molar fraction up to 5.10 -2 , then to decline at higher concentration. TiN x was 20 mol% at DN 2 = 0.51/h, reached about 40 mol% at 1 l/h and remained almost constant while DN 2 increased to 2 l/h. At DN 2 = 2 l/h, about 70 mol% in TiNx was obtained with D SiH2Cl2 = 0.05 l/h. Then from D SiH2Cl2 ranging from 0,1 to 0.2 l/h, TiN x concentration remains almost equal to 35 mol%. A linear dependence in the SiH 2 Cl 2 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.