A model-based methodology for the analysis and design of atomic layer deposition processes—Part II:

This paper demonstrates the experimental validation and mechanistic analysis of the continuous cross-flow atomic layer deposition (ALD) reactor model developed in the first article of this series (Holmqvist et al., in press). A general nonlinear parameter estimation problem was formulated to identify the kinetic parameters involved in the developed ALD gas–surface reaction mechanism, governing ZnO film growth, from ex situ film thickness measurements. The presented methodology for comprehensive model assessment considers the statistical uncertainty of least-squares estimates and its ultimate impact on the model predicted response. Joint inference regions were determined to assess the significance of parameter estimates and results indicate that all estimates involved in the precursor half-reactions were adequately determined. The reparameterization of the Arrhenius equation effectively decreased the characteristically high correlations between Arrhenius parameters, leading to improvement in precision of individual parameter estimates. Model predictions of the spatially dependent film thickness profile with narrow confidence band were in good agreement with both calibration and validation experimental data, respectively, under a wide range of operating conditions. The subsequent extensive theoretical analysis exhibits that the experimentally validated model successfully reproduces the detailed process dynamics revealed by in situ quartz crystal microbalance and quadrupole mass spectroscopy diagnostics, and thereby provides a supplementary analysis tool. Finally, the univariate sensitivity analysis revealed the mechanistic dependence of all the measured process operating parameters on the spatially dependent film thickness profile, resolved at the level of a single pulse sequence. Hence, the presented model-based framework serves as a means to guide future research efforts in the field of ALD process optimization.

► Methodology for estimating kinetic parameters involved in the ALD gas–surface reactions. ► Assessment of the statistical reliability of the parameter estimates and the model response. ► Continuous flow ALD reactor model was validated experimentally and showed high predictability. ► Mechanistic dependence of process operating parameters on ALD film growth profiles were assessed. ► Application of a heuristic optimization algorithm implemented in a cluster environment.