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Copper has been deposited into prepatterned high-aspect-ratio (3:1) trenches using electroplating (EP), CVD and sputter reflow. Filling capability, electrical properties, electromigration lifetimes and mechanical stress are examined. Also, barriers against Cu diffusion are studied using electrical bias at elevated temperatures. CVD Cu can fill high aspect ratio features that electroplating cannot. Sputter-reflowed Cu can also fill high aspect ratio features, but has a high thermal budget for features >0.4 /spl mu/m. Preliminary results show that CVD Cu may be limited by electromigration lifetime.