Surface science investigations of atomic layer deposition half-reactions using TaF5 and Si2H6

Fundamental adsorption and surface chemistry studies of TaF₅ and Si₂H₆ on a polycrystalline Ta surface were performed in ultra-high vacuum (UHV) in the range 303-523 K to understand if these precursors may be used in applications to grow Ta-based films by atomic layer deposition. TaF₅ uptake saturated in UHV conditions for less than 100 L exposure for adsorption on both clean Ta and on 144 L Si₂H₆-treated Ta. TaF₅ dissociatively adsorbed on clean Ta, and F ligands were determined to govern the self-limiting adsorption behavior. The extent of each “half-reaction”, the reaction of TaF₅ with a Si₂H₆-treated surface and the reaction of Si₂H₆ with a TaF₅-treated surface, increased with surface temperature and was dependent on SiH_xF_y byproduct desorption. Neither Si₂H₆ adsorption nor Si₂H₆ half-reaction reached saturation in UHV conditions, as measured by the surface Si concentration. F ligands were removed during the Si₂H₆ half-reaction, and residual F asymtotically approached a constant value.