Method of forming nitride capped cu lines with reduced electromigration along the cu/nitride interface

Abstract

The electromigration resistance of nitride capped Cu lines is significantly improved by controlling the nitride deposition conditions to reduce the compressive stress of the deposited nitride layer, thereby reducing diffusion along the Cu-nitride interface. Embodiments include depositing a silicon nitride capping layer on inlaid Cu at a reduced RF power, e.g., about 400 to about 500 watts and an increased spacing, e.g., about 680 to about 720 mils, to reduce the compressive stress of the deposited silicon nitride layer to below about 2×10 Pascals. Embodiments also include sequentially and contiguously treating the exposed planarized surface of in-laid Cu with a soft plasma containing NH diluted with N , ramping up the introduction of SiH and then initiating plasma enhanced chemical vapor deposition of a silicon nitride capping layer, while maintaining substantially the same pressure and N flow rate during plasma treatment, SiH 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.