Monte Carlo simulation of hyperthermal physical vapor deposition

Low-pressure sputtering and ionized vapor deposition processes create atomic fluxes with kinetic energies in the 1.0-20 eV (and above) range. The impact energy of these hyperthermal atoms significantly effects the surface morphology and structure of vapor deposited films. Recent molecular dynamics simulations of metal atom interactions with a metal surface have established the energy and angular dependence of many of the impact energy induced mechanisms of atomic assembly including biased diffusion, atomic reflection, resputtering, and thermal transient induced "athermal" diffusion. These four effects have been incorporated into an earlier two-dimensional kinetic Monte Carlo model that analyzes the thermally driven multipath diffusional processes active during vapor deposition (Y. G. Yang et al., Acta Mater., 45 (1997) 1445). The contributions of the energy-dependent mechanisms to surface morphology were found to grow in importance as the substrate temperature was reduced and/or as the rate of deposition increased. The simulation method- ology was used to establish functional dependence of surface roughness upon the atom's kinetic energy and its direction of incidence during the hyperthermal deposition of nickel vapor. The simulations reveal the existence of a minimum surface roughness at an incident angle which increased with impact atom kinetic energy. Modification of the impact energy is shown to be a viable means for controlling surface morphology during physical vapor deposition under high deposition rate, low deposition temperature growth conditions.  2001 Published by Elsevier Science Ltd on behalf of Acta Materialia Inc.