Cu has replaced Al as the main interconnection material in ultra-large integrated circuits, reducing resistance capacitance delay and yielding higher electro-migration reliability. As feature size decreases, however, it has become more difficult to produce reliable Cu wiring. We studied a Cu seed layer deposited using plasma enhanced atomic layer deposition (PEALD). The electrical properties of the PEALD Cu thin film with sub-10 nm thickness were determined by the continuities and morphologies of the films. At a deposition temperature of 150 degrees C. the resistivity of Cu thin films was 5.2 mu Omega-cm and the impurity content was below 5 atomic %. Based on these results, Cu seed layers were deposited on 32-nm Ta/SiO(2) trench substrates, and electrochemical plating was performed under conventional conditions. A continuous seed layer was deposited using PEALD, resulting in a perfectly filling of the 32-nm sized trench. (C) 2011 Elsevier B.V. All rights reserved.