Bottom-up metal nitride formation

Vapor deposition processes are provided for bottom up filling of trenches and other structures with metal nitrides such as vanadium nitride and titanium nitride. In some embodiments, VCl4 can be used as an etchant source in the deposition processes. The reaction conditions are selected such that some Cl2 forms in the reaction space and preferentially etches deposited metal nitride at the upper surfaces of a trench or other three-dimensional feature on a substrate. The self-etching during the deposition process facilitates a bottom up filling of the feature and may reduce or eliminate the formation of seams or voids.