Low pressure chemical vapor deposition of silicon nitride using the environmentally friendly tris(dimethylamino)silane precursor

This study investigates the use of the environmentally benign precursor tri(dimethylamino)silane (TDMAS) with NH₃ to synthesize silicon nitride films by low pressure chemical vapor deposition. The growth kinetics are investigated as a function of deposition temperature, total pressure, and NH₃/TDMAS flow ratios. The deposits are found to be essentially stoichiometric and to contain ∼5 at. % carbon when appropriate NH₃ concentrations are present. The films are found in all cases to be amorphous and highly tensile. For optimized processing conditions, values of the refractive index are close to those reported for Si₃N₄. The film density is observed to increase with higher deposition temperatures up to 800°C and then decrease due to the onset of gas phase nucleation effects. This behavior is readily reflected in the etch rate of those films. FTIR spectra reveal the presence of hydrogen even at high deposition temperatures (900°C). Hardness and Young's modulus of the films are seen to increase with higher deposition temperatures, reaching saturation values near 20 and 185 GPa, respectively, above 800°C.