Growth kinetics and characterization of low pressure chemically vapor deposited Si₃N₄ films from (C₄H₉)₂SiH₂ and NH₃

The use of the environmentally benign precursor ditertiarybutylsilane (DTBS) with NH₃ to synthesize silicon nitride films by low pressure chemical vapor deposition was investigated. In the temperature range 600 to 700 °C, the growth rate is observed to follow an Arrhenius behavior with an activation energy of 50 kcal mol^-1, while above 700 °C, the rate decreases with higher temperatures primarily due to the gas phase decomposition of DTBS. The growth rate varied linearly with total pressure over the investigated range of 0.2 to 0.65 Torr and with DTBS flow rate up to a value of 20 sccm in agreement with a Langmuir-Hinshelwood mechanism. A rapid decrease in growth rate was observed with higher NH₃ DTBS ratios due to a reduction in the partial pressure of DTBS and its enhanced competition with NH₃ for available surface sites. All deposits were found to be essentially stoichiometric and to contain ≈ 10 at% carbon. The films were found in all cases to be amorphous and highly tensile. At deposition temperatures below 750 °C, values of the refractive index were near those reported for Si₃N₄. FTIR spectra revealed the presence of hydrogen for even the highest investigated deposition temperature (900 °C). The hardness and Young's modulus of the films increased with higher deposition temperatures reaching values near 19 and 190 GPa, respectively, at 900 °C.