Multiscale investigation of the influence of surface morphology on thin film CVD

We have developed a multiscale CVD model in which we coupled consistently the gas phase and surface dynamics. In particular at the macroscale we solve overall mass, momentum, and energy conservation equations with the finite element method, while at the microscale the morphological evolution of the film is investigated with 3D kinetic Monte Carlo. Macro and microscales are linked together imposing continuity of gas phase concentrations and fluxes at the common boundary. The surface model implemented in KMC takes into account the Si(100)2 × 1 surface reconstruction, and the anisotropic diffusion of H and Si adatoms and dimers. Our simulations show that the diffusion of adsorbed species when most of the surface is covered by hydrogen can hinder the formation of Si dimers, which are favorable Si adsorption sites, affecting the overall growth rate. This indicates that a macroscale model in which an elementary surface kinetic mechanism is implemented cannot predict accurately Si film growth rates at low temperatures, when the surface is mostly covered by adsorbed species. Also, the comparison between experimental and calculated data suggests that a hydrogen desorption mechanism different from the intradimer pathway is active, and that Si adatoms might play a role.