Enhanced Grain Growth of Electroplated Copper on Cobalt-Containing Seed Layer

Cu films with low impurities were electroplated on pure Cu, CuCo alloy and electrodeposited Co seed layers to study the room temperature grain growth behavior. As-evaporated Cu and CuCo alloy seed layers showed a significant enhancement effect on the Cu recrystallization compared with sputtered Cu seed layers and post-annealed evaporated seed layers. The impact of the electrodeposited Co seed layer on the Cu grain growth was found to be dependent on the Co plating chemistry and on the thickness of the Co film. Co films plated in the absence and presence of saccharin showed a crystal structure of fcc and hcp, respectively. While the former showed little to no impact on the Cu recrystallization, the later was found to enhance or hinder the Cu recrystallization depending on the thickness of the Co. Studies on a Cu/Co sandwich stack structure showed that the recrystallization started at the top Cu layer, proceeding to the middle layer and then to the bottom layer. (C) 2013 The Electrochemical Society. All rights reserved.