Challenges in scaling of IPVD deposited Ta barriers on OSG low-k films: Carbonization of Ta by CH_x 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, TaCx, or be redeposited in the pores as CHx polymers. This is evidenced by a decrease in CH3 groups that correlates with an increase in TaCx. The formation of TaCx poses a significant challenge in the back end of line (BEOL) technology when reducing the barrier thickness.