AVS 50th International Symposium
    Surface Science Tuesday Sessions
       Session SS2-TuM

Paper SS2-TuM8
Nucleation Kinetics during Homoepitaxial Growth of TiN(001) by Reactive Magnetron Sputtering

Tuesday, November 4, 2003, 10:40 am, Room 328

Session: Nucleation and Growth
Presenter: M.A. Wall, University of Illinois at Urbana-Champaign
Authors: M.A. Wall, University of Illinois at Urbana-Champaign
D.G. Cahill, University of Illinois at Urbana-Champaign
I. Petrov, University of Illinois at Urbana-Champaign
D. Gall, Rensselaer Polytechnic Institute
J.E. Greene, University of Illinois at Urbana-Champaign
Correspondent: Click to Email
Polycrystalline TiN is extensively used as a diffusion barrier in microelectronics, as a hard wear resistant coating on cutting tools, and as a corrosion and abrasion resistant layer on optical components. The performance of TiN in all these applications is dependant on the texture of the layer, which is in turn a function of the film growth parameters and nucleation kinetics. To gain an atomic-scale understanding of the processes which govern TiN nucleation, we grow epitaxial layers on TiN(001) via reactive magnetron sputtering in an ultra-high vacuum (UHV) system and employ in-situ scanning tunneling microscopy (STM) to investigate the dynamics. In addition, we perform density functional calculations in order to guide the interpretation of our experimental results. The characteristic island size R@sub c@ necessary to nucleate a new layer on a growing island is measured as a function of growth temperature T@sub s@ and nitrogen fraction f@sub N2@ in an Ar/N@sub 2@ mixture. By applying nucleation rate theory to temperature dependant R@sub c@ data obtained from layers grown with f@sub N2@ = 1, we extract a diffusion activation energy E@sub s@ = 1.4±0.1 eV for T@sub s@ @<=@ 865 °C where nucleation is diffusion limited. For T@sub s@ @>=@ 910 °C, nucleation becomes limited by the formation of unstable clusters, and we extract an adspecies formation energy E@sub f@ = 1.4±0.2 eV. When f@sub N2@ is reduced from 1 to 0.1, E@sub s@ = 1.1±0.2 eV which results in a factor of two increase in R@sub c@ at a given T@sub s@. The activation energy we calculate for Ti diffusion on TiN(001) is 0.4 eV, significantly smaller than E@sub s@ extracted from our experiment, indicating that Ti is not the dominant diffusing species. Based on calculated binding energies of TiN@sub x@ clusters, the dominant diffusing species is likely TiN@sub x@, with 1 @<=@ x @<=@ 3.