A real time Monte Carlo simulation of thin film nucleation in localized-laser chemical vapor deposition

A real time Monte Carlo simulation is used to model the nucleation and initial stages of thin film growth during localized-laser chemical vapor deposition (LLCVD). This model includes the effects of laser–substrate heating, heterogeneous pyrolytic decomposition of parent molecules on the laser-heated region of the surface, and adatom migration and desorption dynamics. The amount of material deposited as a function of time is obtained over a surface area of 150×150 Å for various values of the substrate temperature, parent gas pressure, and adsorbate–substrate binding energy. Additional information is obtained about the cluster density, and the role of surface defects and two-atom cluster dynamics on the initial growth rate. The deposition of silicon by heterogeneous pyrolytic decomposition of silane (SiH4) is used as a base case for the simulation. Predictions of the initial thin film morphology and its temporal evolution during static laser heating of micron-dimensional regions of the surface are presented. Simulation results indicate that for a given silane pressure and adsorbate–substrate binding energy, there is a critical temperature Tc such that for laser-induced peak temperatures Tp Tc, nucleation occurs initially in an annulus region centered with respect to the incident laser irradiation. The inclusion of two-atom cluster dynamics in the simulation is shown to increase the value of Tc and alter the initial morphology for low adsorbate–substrate binding energies. The simulation results are extended to scanning LLCVD to predict the maximum scan speed at which nucleation will occur.