Electron Transport Across Cu/Ta(O)/Ru(O)/Cu Interfaces in Advanced Vertical Interconnects

Abstract The vertical resistance of Cu/Ta/Ru/Cu stacks is calculated using a combination of first-principles density functional theory (DFT) and a Non-Equilibrium Green’s Function (NEGF) formalism. The effects of oxidizing either one or both of the Ta and Ru layers are analyzed. These oxides can be either metallic (TaO and RuO 2 ) or insulating (Ta 2 O 5 ) in nature. Simulations indicate that for the metallic oxides, the presence of RuO 2 results in more electron scattering than TaO. Complete oxidation of both Ta/Ru layers results in a ≈ 3 × increase in resistance for Cu/TaO/RuO 2 /Cu relative to the un-oxidized structure, and a ≈ 8 x increase in resistance for Cu/Ta 2 O 5 /RuO 2 /Cu relative to the un-oxidized structure. Electron transmission/reflection coefficients as well as values of total resistance are reported for each interface structure. These results highlight the importance of identifying and controlling oxygen contamination in high-volume manufacturing in order to obtain low resistance vertical interconnects and favorable device performance.