Method of forming capped copper interconnects with reduced hillock formation and improved electromigration resistance

摘要

The electromigration resistance of capped Cu or Cu alloy interconnects is significantly improved by sequentially and contiguously treating the exposed planarized surface of in-laid Cu with a plasma containing NH₃ and N₂, ramping up the introduction of SiH₄ and then initiating deposition of a silicon nitride capping layer. Embodiments include treating the exposed surface of in-laid Cu with a soft NH₃ plasma diluted with N₂, ramping up the introduction of SiH₄ in two stages, and then initiating plasma enhanced chemical vapor deposition of a silicon nitride capping layer, while maintaining substantially the same pressure, N₂ flow rate and NH₃ flow rate during plasma treatment, SiH₄ ramp up and silicon nitride deposition. Embodiments also include Cu dual damascene structures formed in dielectric material having a dielectric constant (k) less than about 3.9.