Optimizing Cu barrier thickness for interconnects performance, reliability and yield

Abstract

Cu barrier thickness optimization on our 90nm pitch Vx/Mx layers with porous ULK SiCOH (κ=2.55) was systematically investigated. Both via resistance and intrinsic EM performance favors thinner TaN and Ta films, however, the robustness of the plating requires thicker Ta to improve seed quality that withstand dissolution during plating. Overall, a thin TaN barrier with moderate thick Ta provides the optimum solution for performance, reliability and yield.