Influence of Minimum Barrier Metal Thickness at Trenches on Void Formation in 50-nm-wide Cu Wiring

In order to completely fill the 50 nm wide high aspect ratio trenches with Cu electroplating, we investigated the influence of barrier metal thicknesses on the voids formation in the trenches. The void occurrence rates were decreased significantly with increasing minimum barrier metal thickness at the side wall of trenches, and it becomes less than 1% when the minimum thickness becomes thicker than 4.6 nm independent of width and aspect ratio of trenches. Resistivities of Cu wires with minimum total barrier metal thickness thicker than 4.6 nm by electroplating, annealing at 573 K for 30 min were found to be almost the same level as those listed in ITRS. (C) The Electrochemical Society of Japan, All rights reserved.