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A model-based methodology for the analysis and design of atomic layer deposition processes-Part III: Constrained multi-objective optimization
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Solid State Electronics.
2013 (English)In: Chemical Engineering Science, ISSN 0009-2509, E-ISSN 1873-4405, Vol. 96, 71-86 p.Article in journal (Refereed) Published
Abstract [en]

This paper presents a structured methodology for the constrained multi-objective optimization (MO) of a continuous cross-flow atomic layer deposition (ALD) reactor model with temporal precursor pulsing. The process model has been elaborated and experimentally validated in the first two papers of this series (33 and 34). A general constrained MO problem (MOP) was formulated to simultaneously optimize quasi-steady-state reactor throughput and overall precursor conversion for the controlled deposition of ZnO films from Zn(C2H5)(2) and H2O, subject to a set of operational constraints. These constraints included lower bounds for the cross-substrate film thickness uniformity and post-precursor purge duration. The non-dominated Pareto optimal solutions obtained successfully revealed the relation between the incommensurable process objectives and reduced the design space of the ALD process into a feasible set of design alternatives. The results presented here show that post-precursor purge duration is essential when optimizing throughput in temporally separated ALD processes, and that this is a major drawback when considering operation at atmospheric pressure. Finally, the robustness of the process along the Pareto optimal front, i.e. the ability of the process to accommodate variations in the associated set of optimal decision variables (DVs), was assessed by Monte Carlo simulations, in which the values of the parametric uncertainties were randomly generated from a multivariate normal distribution. The uncertainty and sensitivity analysis showed that the inherent robustness of the process is progressively lost with the precursor conversion, and revealed the mechanistic dependence of all DVs on the proposed optimization specifications. 

Place, publisher, year, edition, pages
2013. Vol. 96, 71-86 p.
Keyword [en]
Atomic layer deposition, Optimization, Uncertainty and sensitivity analysis, Numerical analysis, Mathematical modeling, Transport processes
National Category
Engineering and Technology
Research subject
Engineering Science with specialization in Electronics
URN: urn:nbn:se:uu:diva-204803DOI: 10.1016/j.ces.2013.03.061ISI: 000320508200007OAI: oai:DiVA.org:uu-204803DiVA: diva2:641037
Available from: 2013-08-15 Created: 2013-08-12 Last updated: 2014-02-03Bibliographically approved

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Törndahl, Tobias
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