(658d) Chemical Vapor Deposition Growth and Characterization of Amorphous, Phosphorous-Doped Ruthenium Films

Chemical vapor deposition growth of amorphous-like ruthenium films containing ~15 percent phosphorous is reported along with the surface reactions that enable the growth of this metallic glass. Dihydridotetrakis(trimethylphosphine) ruthenium was used at growth temperatures ranging from 525 to 575 K. The phosphorous content changed with growth temperature and with film depth. X-ray photoelectron spectroscopy reveals films grown at 575 K contain both phosphorous and ruthenium in the zero-valent state. 30 nm films grown at 575 K are found to be nearly amorphous, with very small crystalline clusters observed near the SiO₂ substrate interface in transmission electron microscopy and with a featureless X-ray diffraction pattern. By comparison 5 to 30 nm ruthenium films deposited by physical deposition at room temperature are polycrystalline, with readily apparent Ru X-ray diffraction features. Surface studies reveal the precursor to dissociatively adsorb on the surface of SiO₂ at the growth temperatures. Adsorption at 210 K reveals a rich surface chemistry that ultimately leads to the desorption of P(CH₃)_xH_y, P(CH₃) ₃ and CH₃ above 285 K. The surface studies and growth studies suggest the trimethylphosphine ligands desorb at the growth conditions and readsorb, and subsequently incorporate the P into the Ru film. Phosphorous and its manner of incorporation appear responsible for the amorphous-like character.