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A model-based methodology for the analysis and design of atomic layer deposition processes—Part III: Constrained multi-objective optimization

Holmqvist, Anders LU ; Torndahl, Tobias and Stenström, Stig LU (2013) In Chemical Engineering Science 96. p.71-86
Abstract
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... (More)
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. (Less)
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author
organization
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type
Contribution to journal
publication status
published
subject
keywords
Atomic layer deposition, Optimization, Uncertainty and sensitivity, analysis, Numerical analysis, Mathematical modeling, Transport processes
in
Chemical Engineering Science
volume
96
pages
71 - 86
publisher
Elsevier
external identifiers
  • wos:000320508200007
  • scopus:84877049721
ISSN
0009-2509
DOI
10.1016/j.ces.2013.03.061
language
English
LU publication?
yes
id
5bbaeb16-f37a-4fcf-8a9d-dd7d40843aae (old id 3979796)
alternative location
http://dx.doi.org/10.1016/j.ces.2013.03.061
date added to LUP
2013-09-02 15:57:23
date last changed
2019-02-27 03:07:22
@article{5bbaeb16-f37a-4fcf-8a9d-dd7d40843aae,
  abstract     = {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.},
  author       = {Holmqvist, Anders and Torndahl, Tobias and Stenström, Stig},
  issn         = {0009-2509},
  keyword      = {Atomic layer deposition,Optimization,Uncertainty and sensitivity,analysis,Numerical analysis,Mathematical modeling,Transport processes},
  language     = {eng},
  pages        = {71--86},
  publisher    = {Elsevier},
  series       = {Chemical Engineering Science},
  title        = {A model-based methodology for the analysis and design of atomic layer deposition processes—Part III: Constrained multi-objective optimization},
  url          = {http://dx.doi.org/10.1016/j.ces.2013.03.061},
  volume       = {96},
  year         = {2013},
}