Numerical Simulation of the Film Distribution During Atomic Layer Deposition within Porous Substrates

Atomic layer deposition (ALD) technology can deposit thin films on porous substrates with sub-nanometer precision, thereby adjusting the pore size and interface properties. Such ALD processes are affected by the diffusion and reaction of precursors, which causes difficulties in studying the reaction kinetics. In this paper, models were established for the depositions on the outer surface and inside the pores of the γ-Al₂O₃ substrate where ZnO films were formed via ALD. A sensitivity analysis was carried out for the two models through numerical simulation, which led to the formulas of surface coverage of the deposits. The results show that during the deposition on the outer surface of the substrate, with the increase of adsorption rate constant k_a, the conversion rate constant k₁ of adsorbed diethyl zinc to monoethyl zinc, the hydroxyl concentration C_OH, and the decrease of the desorption rate constant k_d, the film deposition accelerates. For the deposition inside the pores, higher C_OH and lower diffusion coefficient D_S result in deposit formation in a shallow position. The analytical formulas can accurately predict the deposit coverage and its distribution on the outer surface and inside the pores of porous substrates.