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 SiHxFy 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.