Atomic layer deposition of TaSi x thin films on SiO 2 using TaF 5 and Si 2H 6

Abstract

The atomic layer deposition (ALD) of TaSi x thin films was achieved on SiO 2 at 500 K through the repetition of separate, alternating exposures to TaF 5 and Si 2H 6. Films were deposited and in situ analyzed by X-ray photoelectron spectroscopy (XPS) to evaluate growth kinetics, interfacial chemistry with the substrate, and film composition. The first 25 exposure cycles resulted in an average film thickness of only 0.3 nm. Afterward, film thickness increased linearly at a rate of ∼0.1 nm/cycle, and films deposited using 50 ALD cycles were about 2.5 nm thick. The formation of a Ta oxyfluoride interfacial compound was observed and attributed to the reaction of TaF 5 with SiO 2, based upon previous surface chemistry studies. After 150 cycles, films were thick enough to suppress photoelectrons from the substrate and substrate film interface. Based on XPS data, the surface composition of these as-grown films, which were cooled in Si 2H 6, was in atomic percent: 26.6% Ta, 51.3% Si, 17.9% F, 1.6% O and 2.6% C. After 30 s of sputtering with 5 keV Ar ions, the F XPS signal was at the noise level indicating negligible fluorine incorporation in the films. The Ta 4f and Si 2p XP spectra are consistent with zero-valent Ta and Si, most likely as a non-stoichiometric tantalum silicide-like phase.