Reliability Enhancement of Copper/Porous SiOCH Metallization Systems Using Nitrogen Stuffing and Bias-Filter Sputter Deposited Mn₂O₃ Barrier

Abstract

A robust ultrathin barrier to retard Cu diffusion is needed for fabricating state-of-the-art Cu interconnects associated with porous dielectric materials. Gas stuffing of grain boundaries is widely used to strengthen conventional polycrystalline TiN and TaN barriers. Alternatively, a self-formed MnOx layer derived typically from sputter-deposited Cu(Mn) alloy film is a viable barrier. However, vacuum plasma generated during Cu(Mn) deposition tends to damage porous dielectric materials. Thus, this study combines the two approaches, proposing a strategy to enhance reliability of copper/porous carbon-doped organosilica (p-SiOCH) metallization systems using nitrogen stuffed p-SiOCH and bias-filter sputter deposited Mn2O3. An ultrathin (1–4 nm) Mn2O3 film, deposited by reactive sputtering with a biased-filter mechanism on nitrogen-stuffed p-SiOCH (p-SiOCH(N)), was proposed as a barrier layer to prevent Cu from diffusion. Electrical properties of the samples were evaluated by capacitance-voltage and current density-electric field measurements. The bias-filter mechanism eliminated plasma damage of the p-SiOCH(N) layers. Furthermore, stabilization annealing converted Mn2O3 to Mn2O3-x(N) (manganese sub-oxynitride), giving the highest barrier performance for the Cu metallization layer, while maintaining the pristine dielectric properties of the p-SiOCH(N) layers. The Cu/Mn2O3-x(N)/p-SiOCH(N) structure also exhibited extremely low leakage currents after reliability tests, indicting their applicability to Cu metallization.