The formation of a copper silicide interfacial layer by surface reaction in a plasma enhanced chemical vapour deposition (PECVD) system has been studied. Tri-methyl silane (TMS, SiH(CH 3) 3) has been employed as the Si source as an alternative to more conventional silane (SiH 4) approach. TMS precursor has been chosen due to improved control of Si penetration into the copper S. Chhun, L.G. Gosset, N. Casanova, J.F. Guillaumond, P. Dumont-Girard, X. Fedespiel, R. Pantel, V. Arnal, L. Arnaud, J. Torres, Microelectronic Engineering 76 (2004) 106–112. AFM, SIMS, light scattering, FT-IR spectroscopy and dielectric constant measurements were performed on various stacks to evaluate CuSiN formation. Resistance, leakage, and electromigration (EM) reliability characterization were performed on test structures based on 65 nm design rules. Nitridation step in silicidation process was shown to have positive impact on EM reliability, minimizing the line resistance increase.