An ultrathin (e.g., ≤ 2 nm) barrier is needed for fabricating Cu interconnects associated with porous low-k (p-SiOCH) dielectrics with a high aspect ratio trenches/vias in the ultra large scale integrated circuits. To implement successfully the ultrathin Mn oxide barrier on the p-SiOCH dielectric for Cu interconnection, understanding is needed of how the Mn oxide is formed. This study investigated a 2-nm-thick Mn oxide film, deposited by sputtering with a biased-filter intermediating, as the barrier layer to prevent Cu from diffusion. Phase formation of the as-deposited Mn oxide was examined by X-ray photoelectron spectroscopy and X-ray absorption near edge spectroscopy to confirm the formation of Mn 2 O 3 . The experimental results indicated that the formation of Mn 2 O 3 barrier is highly effective in preventing the Cu film from diffusion and agglomeration. Thermal stability of the Cu film increased up to 550 • C, 250 • C greater than the p-SiOCH dielectric without the Mn 2 O 3 film, when combining the nitrogen-stuffed treatment on the p-SiOCH dielectric and annealed the Mn 2 O 3 before the Cu deposition. The structures of Mn 2 O 3 barrier and p-SiOCH dielectric after nitrogen-stuffing treatments were analyzed to evaluate their applicability in Cu interconnects.

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.