Time‐scale analysis of atomic layer deposition processes: Predicting the transition from mass‐transfer to kinetically limited regimes

Abstract

AbstractThe relative rates of adsorption and irreversible reaction are modeled for a prototypical atomic layer deposition (ALD) system. Surface species balance modeling equations are processed through a reaction factorization procedure to eliminate redundant dynamic modes. The resulting singular perturbation problem then is used to develop a criterion that distinguishes between mass‐transfer and kinetically‐limited deposition regimes for this dynamic process. Detailed simulations of a TMA/water alumina ALD process are used to evaluate our analysis approach and to demonstrate the dominance of mass‐transfer limitations for this system during both precursor exposure periods. Our analysis shows the increasing likelihood of encountering mass‐transfer limitations at reduced temperatures, a finding opposite of what might be expected. We find that the ALD dynamics evolve on a manifold defined by the balancing of adsorption and irreversible reaction rates, further reducing the dynamic dimension of the deposition dynamics. (© 2015 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)