GROWTH-KINETICS AND CHARACTERIZATION OF LOW-PRESSURE CHEMICALLY VAPOR-DEPOSITED SI3N4 FILMS FROM (C4H9)(2)SIH2 AND NH3

The use of the environmentally benign precursor ditertiarybutylsilane (DTBS) with NH3 to synthesize silicon nitride films by low pressure ch emical vapor deposition was investigated. In the temperature range 600 to 700 degrees C, the growth rate is observed to follow an Arrhenius behavior with an activation energy of 50 kcal mol(-1), while above 700 degrees C, the rate decreases with higher temperatures primarily due to the gas phase decomposition of DTBS. The growth rate varied linearl y 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 seem in agreement with a L angmuir-Hinshelwood mechanism. A rapid decrease in growth rate was obs erved with higher NH3/DTBS ratios due to a reduction in the partial pr essure of DTBS and its enhanced competition with NH3 for available sur face sites. All deposits were found to be essentially stoichiometric a nd to contain approximate to 10 at% carbon. The films were found in al l cases to be amorphous and highly tensile. At deposition temperatures below 750 degrees C, values of the refractive index were near those r eported for Si3N4. FTIR spectra revealed the presence of hydrogen for even the highest investigated deposition temperature (900 degrees C). The hardness and Young's modulus of the films increased with higher de position temperatures reaching values near 19 and 190 GPa, respectivel y, at 900 degrees C.