Effect of Annealing on the Microstructure and Electrical Property of RuN Thin Films

Abstract

Ruthenium (Ru) and ruthenium nitride (RuN) thin films have been investigated as candidates for barrier layers in copper (Cu) damascene processes. In order to study the thermal stability of the Ru and RuN films, the as-deposited films were annealed by rapid thermal annealing (RTA), and the film resistance was real-time measured by a four-point probe, which was embedded in the RTA tool. The X-ray diffraction data show that the grain size of Ru decreased with the increase of the nitrogen (N) content. The Ru phases gradually changed to the RuN phases, and the resistivity of the RuN films decreased with annealing time due to nitrogen effusion. Discontinuous RuN films were found when the annealing temperature was higher than 800 degrees C and then caused a poor Cu diffusion barrier property. We also demonstrated that the Cu film could be directly electroplated on the RuN films with adequate adhesion. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3537825] All rights reserved.