TIN-TIXSIY CODEPOSITS APCVD PRODUCED USING THE TICL4-N-2-SIH2CL2-H-2 SYSTEM

Mixtures of TiNx, TiSi2 and Ti5Si3(N) were chemically vapour codeposit ed at atmospheric pressure using the TiCl4 - N-2 - SiH2Cl2 - H-2 syste m. Compact materials with very intimately dispersed phases and with co ntrolled composition were obtained between 825 - 875 degrees C and usi ng flow rate ranges : 0.5 less than or equal to D-N2 less than or equa l to 2.5, and 0.05 less than or equal to D-SiH2Cl2 a 0.2 (in l/h). D-T iCl4 and D-H2 were kept constant at 0.183 and 30 (in l/h) respectively . According to the Ti-Si-N ternary phase diagram, TiNx with x = 0.95 /- 0.05, TiSi2 and Ti5Si3(N), corresponding to some solubility of nitr ogen into Ti5Si3, were in thermodynamical equilibrium. At 850 degrees C, D-TiCl4 = 0.183 and D-H2 = 30 (in l/h), the effect of N-2 and SiH2C l2 input concentrations were studied. At D-SiH2Cl2 = 0.1 l/h, the depo sition 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 concentr ation. TiNx was 20 mol% at D-N2 = 0.5 1/h, reached about 40 mol% at 1 l/h and remained almost constant while D-N2 increased to 2 l/h. At D-N 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, TiNx concentratio n remains almost equal to 35 mol%. A linear dependence in the SiH2Cl2 concentration was observed for the growth rate. The relationship betwe en the logarithmic plot of the growth rate versus the reciprocal of co deposition temperature (in Kelvin) was linear and an apparent activati on energy of 105 kJ/mol was calculated. The effect of temperature on t he TiNx preferred orientations was also evidenced.