Seedless Copper Electrochemical Deposition on Air Exposed TaN Barrier Layers with Pd and Ru Adhesion Promoters

Abstract

A method is presented for the direct plating of copper on plasma enhanced atomic layer deposited (PE-ALD) palladium for ULSD applications. While the nucleation and growth of copper directly onto TaN is possible, difficulties arise with the growth of adherent, uniform, conformal layers. This study examines the possibility of depositing a thin interlayer, (essentially a seed layer) that is sufficiently thin that it does not compromise the resistance of the copper, and provides a conformal seed layer for the subsequent electrodeposition step, without the problems associated with line-of-site techniques such as PVD for aggressive ULSD features. Cu deposition was performed on both patterned trench structures and on planar substrates of PE-ALD Pd on air-exposed tantalum nitride. Successful copper deposition was obtained from conventional bath formulations, and clear superfilling behavior was observed.