Cu has replaced Al as an interconnection material in ultra-large integrated circuits, reducing resistance capacitance delay and yielding higher electro-migration reliability. However, as the feature size decreases, it becomes more difficult to produce reliable Cu wiring. In this work, the Plasma Enhanced Atomic Layer Deposition (PEALD) of Cu seed layers deposited on Ta substrates (both with and without NH3 plasma pretreatment) was investigated. The Cu seed layers deposited on NH3 plasma-pretreated Ta substrates were found to have favorable properties compared to films deposited without plasma pretreatment because of an increase in the surface energy and of the Ta substrate, which resulted in improved surface wetting.