MODELING OF GAS-PHASE PROCESSES IN LASER-INDUCED CHEMICAL VAPOR-DEPOSITION FROM CR(CO)6 WITH AN EXCIMER LASER

Laser-induced chemical vapor deposition from Cr(CO)6 with an excimer laser has been modeled and simulated to investigate the kinetics and mechanisms of the deposition. The model concerns gas-phase processes including photolysis of Cr(CO)6, transportation of photofragments to the substrate surface, and elimination of photofragments through chemical reactions during transportation. The photofragments are eliminated through the reforming to Cr(CO)6 that is divided into the two stages: stabilization of the photofragments in excited states by collisions with buffer gases (CO, Ar) and recombination of the photofragments in the ground state with CO. The simulation shows that the deposition rate without additional buffer gases is of the same order as the experimental rate and that deposition rates in the presence of additional CO and Ar agree qualitatively with experimental results. This suggests that the supply of Cr species to the substrate surface is mainly controlled by the gas-phase processes where the chemical reactions eliminating photofragments play an important role. Applications of the model for the deposition under other conditions are discussed.