In Situ Two-Step Plasma Enhanced Atomic Layer Deposition of Ru/RuNx Barriers for Seedless Copper Electroplating

Abstract

The study prepared Ru/RuNx bilayer barriers on mesoporous SiO(2) (mp-SiO(2)) dielectric layers for direct Cu electroplating applications using in situ two-step plasma-enhanced atomic chemical vapor deposition (PEALD). For the 5 nm thick Ru/RuNx bilayer deposited at 200 degrees C, obvious thermal decomposition begins at temperatures lower than 400 degrees C. Copper can be successfully electroplated on the as-deposited Ru/RuNx bilayer, and the Cu/Ru/RuNx/mp-SiO(2) film stack can withstand thermal treatment at temperatures up to 500 degrees C without significant physical and chemical degradations according to TEM and SIMS analyses. The study shows that the electroplated Cu layer behaves like a passivation layer that improves the thermal stability of the Ru/RuNx barrier during the thermal annealing. Pull-off tensile test shows that interfaces in the Cu/Ru/RuNx/mp-SiO2 film stack have good adhesion strength, but delamination occurs at the interface between the Ru/RuNx bilayer and the mp-SiO2 layer at 600 degrees C, resulting in Cu and Ru diffusion into the dielectric layer. The study has demonstrated that the PEALD Ru/RuNx bilayer structure prepared using the in situ two-step approach is suitable for the seedless Cu electroplating process in nanometer scale interconnect technology. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3554734] All rights reserved.