Surface reaction kinetics in atomic layer deposition: An analytical model and experiments

Abstract

Atomic layer deposition (ALD) surface reactions are comprised of several elementary surface interactions (such as physisorption, desorption, and chemisorption) occurring at the substrate. Since ALD processes are often far from thermodynamic equilibrium, the surface saturation behavior is controlled by the kinetics of these involved interactions. In this article, we present a first-order kinetic model for ALD reaction, to simulate the cumulative effect of precursor exposure (tA), post-precursor purge (tP1), reactant exposure (tB), post-reactant purge (tP2), and substrate temperature (Tsub) on the resulting growth per cycle (GPC) in an ABAB… pulsed ALD process. Furthermore, to simulate the effect of inadequate reactor purges (tP1, and/or tP2) and undesired non-ALD side reactions, reaction pathways to account excess GPC are also taken into consideration. From our model calculations, we simulate GPC vs Tsub trends observed in ALD growth experiments and demonstrate that the process temperature window (ΔTALD) for a constant GPC depends upon the deposition cycle parameters tA, tP1, tB, and tP2. The modeled GPC vs Tsub trends are discussed and compared with SiNx, ZrN, and ZnO PEALD growth experiments.