SIMULATION OF COLLIMATED FLUX DISTRIBUTIONS DURING PHYSICAL VAPOR-DEPOSITION

We use the Monte Carlo simulations to estimate flux distributions leav ing a single hexagonal collimator cell and on the surface of a flat su bstrate. We assume the Maxwellian flux distribution for the species en tering the collimator, and that the pressure is low enough that the tr ansport inside the collimator cells is collisionless. Flux distributio ns at the exit of a collimator cell are obtained as functions of posit ion in the plane of the collimator exit. The dependence of flux on the angle measured relative to collimator axis (theta) is broader at the corner of the collimator exit than that at the center of the collimato r exit. The fluxes leaving the center of the collimator cell and avera ged over the entire cell exit do not depend on the angle measured arou nd the axis of the collimator cell (phi). At each corner of the collim ator, there is a maximum in the flux at the phi value corresponding to that corner. We simulate both collisionless and collisional transport from the collimator exit to the flat substrate and estimate the flux distributions of species as functions of position on the flat wafer su rface due to a single collimator cell. Tie flux distributions as a fun ction of position for the entire collimator are obtained by summing fl uxes from all contributing collimator cells. The flux distributions on the flat substrate due to the entire collimator do not depend on phi. The theta dependencies of the fluxes on a hat substrate depend on the position of the substrate relative to the collimator cell. Collisiona l transport from the collimator exit to the substrate broadens flux di stributions on the flat substrate, relative to collisionless transport .