AVS 50th International Symposium
    Surface Science Monday Sessions
       Session SS3-MoM

Paper SS3-MoM3
Surface Characterization and Inter-diffusion Study of Copper on Ruthenium Thin Film Deposited on Silicon Substrate

Monday, November 3, 2003, 9:00 am, Room 328

Session: Surface Diffusion and Wetting
Presenter: T. Arunagiri, University of North Texas
Authors: O. Chyan, University of North Texas
T. Arunagiri, University of North Texas
R. Chan, University of North Texas
R.M. Wallace, University of North Texas
M.J. Kim, University of North Texas
T.G. Hurd, Texas Instruments
Correspondent: Click to Email
The dual-damascene patterning processing, coupled with the bottom-up Cu electrofill of damascene features and chemical-mechanical planarization, will continue to be the key for the future success of advanced IC chips. Recent advances in physical vapor deposition development allow highly engineered Ta/TaN diffusion barrier to be extended through 90 nm node. However, the tri-layer Cu-seed/Ta/TaN will likely encounter scaling difficulties in the Cu damascene trench/via features of advanced 65 and 45 nm nodes. We recently reported, J. Electrochem. Soc., 150, C347(2003), that Ruthenium (Ru) metal can function as a directly plate-able, seedless barrier materials. In this presentation, we report new findings centered on the interfacial and inter-diffusion studies of Cu/Ru system. Specifically, comparative study of wetting properties between electroplated-Cu and PVD-Cu on Ru barrier film (~ 10 nm) was carried out by XPS, SEM and AFM. Both electroplated and PVD Cu were found to wet well on Ru, based on SEM, AFM imaging and the scribe/peeled test, before and after thermal annealing over 450C. A strong adhesion between Cu/Ru interconnect microstructures is critical in order to withstand the demanding chemical-mechanical planarization process. Interfacial profiling was performed on Cu/Ru/Si samples using secondary ions mass spectroscopy (SIMS) depth profiling. To avoid knock-in ion-mixing interference, SIMS profiling was directed through the silicon back substrate. The backside SIMS profiling through Cu/Ru/Si samples show distinct interfaces without Cu inter-diffusion after annealed at 450C. TEM was further used to provide detailed cross-sectional imaging of Cu/Ru/Si interfaces. The wetting and inter-diffusion data of Cu/Ru systems will be discussed in the context of Cu diffusion barrier application.