Challenges in scaling of IPVD deposited Ta barriers on OSG low-k films: Carbonization of Ta by CHx radicals generated through VUV-induced decomposition of carbon-containing groups

The effect of vacuum ultraviolet (VUV) radiation during ionized physical vapor deposition (IPVD) of tantalum barriers on various porous organosilicate glass low-k SiCOH films is studied using advanced diagnostics and quantum chemical calculations. VUV photons break the Si–C bonds, releasing hydrocarbon radicals from the pore surfaces. These radicals, trapped in pores that are partially sealed by tantalum deposition, can either react with tantalum to form carbide-like compounds, TaC_x, or be redeposited in the pores as CH_x polymers. This is evidenced by a decrease in CH₃ groups that correlates with an increase in TaC_x. The formation of TaC_x poses a significant challenge in the back end of line (BEOL) technology when reducing the barrier thickness.