AVS 50th International Symposium
    Electronic Materials and Devices Thursday Sessions
       Session EM-ThM

Paper EM-ThM10
Evaluating Ruthenium Thin Film Deposited on Silicon as a Directly Plate-able Cu Diffusion Barrier

Thursday, November 6, 2003, 11:20 am, Room 321/322

Session: Materials for Interconnects and Contacts to Semiconductors
Presenter: O. Chyan, University of North Texas
Authors: O. Chyan, University of North Texas
T.G. Hurd, Texas Instruments
R.M. Wallace, University of North Texas
M.J. Kim, University of North Texas
R. Chan, University of North Texas
T. Arunagiri, University of North Texas
Correspondent: Click to Email
Tantalum (Ta) and tantalum nitride (TaN) bilayer diffusion barrier is currently used in the fabrication of 130 nm integrated circuits to ensure the electrical integrity of the copper interconnects. Thin Ta/TaN are too resistive to plate Cu effectively, additional Cu-seed layer is deposited on Ta/TaN to carry the required current for copper electrofill. However, the Cu-seed/Ta/TaN tri-layer configuration will encounter severe scaling difficulties at the 45 nm node where ultra-thin barrier is need to minimize effects on interconnect resistivity. In this paper, we explore using ruthenium (Ru) as a new Cu diffusion barrier to afford direct Cu plating without the additional Cu-seed layer. Ru is an air stable transition metal with high melting point (2310 C) and is nearly twice as thermally and electrically conductive as Ta. More importantly Ru, like Ta, shows negligible solid solubility with Cu even at 900 C. The preparation and interfacial characterization of Cu thin film on both Ru metal surface and Ru thin film (<10 nm) sputtered on silicon wafer substrate will be discussed. Both dry (magnetron sputtering) and wet (electrodeposition) preparation routes were employed to deposit Cu on Ru. We will present un-published results that demonstrate efficient Cu plating (over 95% efficiency) was achieved on a ~8 nm an ultra-thin film of Ru metal deposited on silicon wafer. The nucleation and growth of Cu deposited layer on Ru was studied by the current transient techniques. The Cu deposited Ru thin film samples (Cu/Ru) were characterized by XPS, SEM, AFM. XRD and SIMS depth profiling. The observed direct Cu-plating on the ultra thin Ru film with excellent adhesion and the effective barrier performance properties based on SIMS depth-profiling and sheet resistance measurements underscores the potential of Ru as an effective direct plate-able Cu diffusion barrier for the advanced 65 and 45 nm nodes.