The present invention provides methods of selectively depositing refractory metal and metal nitride cap layers onto copper lines inlaid in a dielectric layer. The methods result in formation of a cap layer on the copper lines without significant formation on the surrounding dielectric material. The methods typically involve exposing the copper lines to a nitrogen-containing organo-metallic precursor and a reducing agent under conditions that the metal or metal nitride layer is selectively deposited. In a particular embodiment, an amino-containing tungsten precursor is used to deposit a tungsten nitride layer. Deposition methods such as CVD or ALD may be used.