The Experts below are selected from a list of 306 Experts worldwide ranked by ideXlab platform

Panagiotis D Christofides - One of the best experts on this subject based on the ideXlab platform.

  • multiscale computational fluid dynamics modeling of thermal atomic layer deposition with application to chamber design
    Chemical Engineering Research & Design, 2019
    Co-Authors: Yichi Zhang, Yangyao Ding, Panagiotis D Christofides
    Abstract:

    Author(s): Zhang, Yichi | Advisor(s): Christofides, Panagiotis D. | Abstract: This work develops a first-principles-based three-dimensional, multiscale computational fluid dynamics (CFD) model, together with reactor geometry optimizations, of SiO2 thin-Film thermal atomic layer deposition (ALD) using bis(tertiary-butylamino)silane (BTBAS) and ozone as precursors. Specifically, an accurate macroscopic CFD model of the ALD reactor chamber gas-phase development is integrated with a detailed microscopic kinetic Monte-Carlo (kMC) model that was developed in [1], accounting for the microscopic lattice structure, atomic interactions and detailed surface chemical reactions. The multiscale information exchange and the transient simulation of the microscopic distributed kMC algorithms and the macroscopic CFD model are achieved through a parallel Processing message passing interface (MPI) structure. Additionally, density functional theory (DFT)-based calculations are used compute the key thermodynamic and kinetic parameters for the microscopic thin-Film Growth Process. Recognizing the transient non-uniformity and the possibility to reduce the current ALD cycle time, the optimal configuration of reactor geometry is designed including a showerhead panel adjustment and geometry modifications on reactor inlet and upstream. It is demonstrated that with suitable reactor chamber design the required BTBAS ALD half-cycle time can be reduced by 39.6%.

  • Controller and Estimator Design for Regulation of Film Thickness, Surface Roughness, and Porosity in a Multiscale Thin Film Growth Process
    Industrial & Engineering Chemistry Research, 2010
    Co-Authors: Xinyu Zhang, Gangshi Hu, Gerassimos Orkoulas, Panagiotis D Christofides
    Abstract:

    This work focuses on simultaneous regulation of Film thickness, surface roughness, and porosity in a multiscale model of a thin Film Growth Process using the inlet precursor concentration as the manipulated input. Specifically, under the assumption of continuum, a partial differential equation model is first derived to describe the dynamics of the precursor concentration in the gas phase. The thin Film Growth Process is modeled via a microscopic kinetic Monte Carlo simulation model on a triangular lattice with vacancies and overhangs allowed to develop inside the Film. Closed-form dynamic models of the thin Film surface profile and porosity are developed and used as the basis for the design of model predictive control algorithms to simultaneously regulate Film thickness, surface roughness, and porosity. Both state feedback and porosity estimation-based output feedback control algorithms are presented. Simulation results demonstrate the applicability and effectiveness of the proposed modeling and control approach by applying the proposed controllers to the multiscale model of the thin Film Growth Process.

  • CDC - Simultaneous regulation of Film thickness, surface roughness and porosity in a multiscale thin Film Growth Process
    Proceedings of the 48h IEEE Conference on Decision and Control (CDC) held jointly with 2009 28th Chinese Control Conference, 2009
    Co-Authors: Gangshi Hu, Gerassimos Orkoulas, Xinyu Zhang, Panagiotis D Christofides
    Abstract:

    This work focuses on simultaneous regulation of Film thickness, surface roughness and porosity in a multiscale model of a thin Film Growth Process using the inlet precursor concentration as the manipulated input. Specifically, a continuous macroscopic partial differential equation model is used to describe the dynamics of the gas phase. The thin Film Growth Process is modeled via a microscopic kinetic Monte Carlo simulation model on a triangular lattice with vacancies and overhangs allowed to develop inside the Film. Closed-form dynamic models of thin Film surface profile and porosity are developed and used as the basis for the design of a model predictive control algorithm to simultaneously regulate Film thickness, surface roughness and Film porosity. Simulation results demonstrate the applicability and effectiveness of the proposed modeling and control approach by applying the proposed controller to the multiscale model.

  • Stochastic Modeling and Simultaneous Regulation of Surface Roughness and Porosity in Thin Film Deposition
    Industrial & Engineering Chemistry Research, 2009
    Co-Authors: Gangshi Hu, Gerassimos Orkoulas, Panagiotis D Christofides
    Abstract:

    This work focuses on stochastic modeling and simultaneous regulation of surface roughness and porosity for a porous thin Film deposition Process modeled via kinetic Monte Carlo (kMC) simulation on a triangular lattice. The microscopic model of the thin Film Growth Process includes adsorption and migration Processes. Vacancies and overhangs are allowed inside the Film for the purpose of modeling thin Film porosity. The definition of the surface height profile is first introduced for a porous thin Film deposition taking place in a triangular lattice. The dynamics of surface height of the thin Film are described by an Edwards-Wilkinson (EW) type equation, which is a second-order linear stochastic partial differential equation (PDE). The root-mean-square (RMS) surface roughness is chosen as one of the controlled variables. Subsequently, an appropriate definition of Film site occupancy ratio (SOR) is introduced to represent the extent of porosity inside the Film and is chosen as the second to-be-controlled var...

  • Simultaneous regulation of Film thickness, surface roughness and porosity in a multiscale thin Film Growth Process
    Proceedings of the 48h IEEE Conference on Decision and Control (CDC) held jointly with 2009 28th Chinese Control Conference, 2009
    Co-Authors: Gangshi Hu, Gerassimos Orkoulas, Xinyu Zhang, Panagiotis D Christofides
    Abstract:

    This work focuses on simultaneous regulation of Film thickness, surface roughness and porosity in a multiscale model of a thin Film Growth Process using the inlet precursor concentration as the manipulated input. Specifically, a continuous macroscopic partial differential equation model is used to describe the dynamics of the gas phase. The thin Film Growth Process is modeled via a microscopic kinetic Monte Carlo simulation model on a triangular lattice with vacancies and overhangs allowed to develop inside the Film. Closed-form dynamic models of thin Film surface profile and porosity are developed and used as the basis for the design of a model predictive control algorithm to simultaneously regulate Film thickness, surface roughness and Film porosity. Simulation results demonstrate the applicability and effectiveness of the proposed modeling and control approach by applying the proposed controller to the multiscale model.

Nikolaus Dietz - One of the best experts on this subject based on the ideXlab platform.

  • Real time optical characterization of gas flow dynamics in high-pressure chemical vapor deposition
    Journal of Vacuum Science and Technology, 2004
    Co-Authors: Vincent Woods, H. Born, Martin Strassburg, Nikolaus Dietz
    Abstract:

    While low-pressure chemical vapor deposition (CVD) methods offer excellent pathways for many compound semiconductors, these Growth techniques possess limitations in the Growth of high quality compounds with large thermal decomposition pressure such as InN and related materials. To study and extend the Growth towards elevated pressures a high-pressure CVD system with integrated real time optical characterization techniques has been established. The built-in real time monitoring techniques allow the characterization of gas flow kinetics, precursor decomposition kinetics, as well as the crucial steps of nucleation and Film formation. In this contribution, we report the characterization of Process parameter under which the thin Film Growth Process can be maintained under laminar flow condition. Laser light scattering has been proven as the most robust optical tool to characterize the onset of turbulence. Hence, it allows the mapping the pressure and flowing regime under which laminar flow can be maintained.

  • Real-time optical characterization of thin Film Growth
    Materials Science and Engineering B-advanced Functional Solid-state Materials, 2001
    Co-Authors: Nikolaus Dietz
    Abstract:

    The further spatial reduction together with stringent thickness and composition tolerances in manufacturing of advanced electronic and optical devices require new approaches to control the Growth Process as well as to improve the insight into the deposition Process itself. The development of non-invasive, real-time, structure-specific analytical tools for characterizing phenomena occurring at surfaces and interfaces during thin Film Growth has therefore to address both, providing a detailed understanding of the thin Film Growth Process and providing robust Process control signals in real-time. This review gives an overview of the principles of angle resolved reflectance techniques applied to real-time thin Film Process monitoring, the study of surface reaction kinetics, and to Growth Process control. The capabilities of high-sensitive thin Film Growth monitoring and control are illustrated for the Growth of III-V compounds under pulsed chemical beam epitaxy conditions, using p-polarized reflectance spectroscopy as an example.

I. Hirabayshi - One of the best experts on this subject based on the ideXlab platform.

  • Novel understanding of the YBa2Cu3O7-x thin Film Growth
    Journal of Materials Research, 2002
    Co-Authors: D.x. Huang, Y Nakamura, Y. Yamada, I. Hirabayshi
    Abstract:

    By combining the cross-sectional observation of the randomly oriented Film areas and the analyses of the Film microstructural influence by the substrate-surface morphology, we achieved a novel understanding of the YBa 2 Cu 3 O 7 - x (YBCO) thin Film Growth Process, which leads to an explanation of different microstructures formed in YBCO thin Films. Selective and competitive Growth of YBa 2 Cu 3 O 7 - x and Ba-Cu-O/Cu-O was found to occur in the whole Film Growth Process depending on the local surface roughness in which the interfacial energy played a controlling role.

  • Novel understanding of the YBa_2Cu_3O_7–x thin Film Growth
    Journal of Materials Research, 2002
    Co-Authors: D.x. Huang, Y Nakamura, Y. Yamada, I. Hirabayshi
    Abstract:

    By combining the cross-sectional observation of the randomly oriented Film areas and the analyses of the Film microstructural influence by the substrate-surface morphology, we achieved a novel understanding of the YBa_2Cu_3O_7– x (YBCO) thin Film Growth Process, which leads to an explanation of different microstructures formed in YBCO thin Films. Selective and competitive Growth of YBa_2Cu_3O_7– x and Ba–Cu–O/Cu–O was found to occur in the whole Film Growth Process depending on the local surface roughness in which the interfacial energy played a controlling role.

Gangshi Hu - One of the best experts on this subject based on the ideXlab platform.

  • Controller and Estimator Design for Regulation of Film Thickness, Surface Roughness, and Porosity in a Multiscale Thin Film Growth Process
    Industrial & Engineering Chemistry Research, 2010
    Co-Authors: Xinyu Zhang, Gangshi Hu, Gerassimos Orkoulas, Panagiotis D Christofides
    Abstract:

    This work focuses on simultaneous regulation of Film thickness, surface roughness, and porosity in a multiscale model of a thin Film Growth Process using the inlet precursor concentration as the manipulated input. Specifically, under the assumption of continuum, a partial differential equation model is first derived to describe the dynamics of the precursor concentration in the gas phase. The thin Film Growth Process is modeled via a microscopic kinetic Monte Carlo simulation model on a triangular lattice with vacancies and overhangs allowed to develop inside the Film. Closed-form dynamic models of the thin Film surface profile and porosity are developed and used as the basis for the design of model predictive control algorithms to simultaneously regulate Film thickness, surface roughness, and porosity. Both state feedback and porosity estimation-based output feedback control algorithms are presented. Simulation results demonstrate the applicability and effectiveness of the proposed modeling and control approach by applying the proposed controllers to the multiscale model of the thin Film Growth Process.

  • CDC - Simultaneous regulation of Film thickness, surface roughness and porosity in a multiscale thin Film Growth Process
    Proceedings of the 48h IEEE Conference on Decision and Control (CDC) held jointly with 2009 28th Chinese Control Conference, 2009
    Co-Authors: Gangshi Hu, Gerassimos Orkoulas, Xinyu Zhang, Panagiotis D Christofides
    Abstract:

    This work focuses on simultaneous regulation of Film thickness, surface roughness and porosity in a multiscale model of a thin Film Growth Process using the inlet precursor concentration as the manipulated input. Specifically, a continuous macroscopic partial differential equation model is used to describe the dynamics of the gas phase. The thin Film Growth Process is modeled via a microscopic kinetic Monte Carlo simulation model on a triangular lattice with vacancies and overhangs allowed to develop inside the Film. Closed-form dynamic models of thin Film surface profile and porosity are developed and used as the basis for the design of a model predictive control algorithm to simultaneously regulate Film thickness, surface roughness and Film porosity. Simulation results demonstrate the applicability and effectiveness of the proposed modeling and control approach by applying the proposed controller to the multiscale model.

  • Stochastic Modeling and Simultaneous Regulation of Surface Roughness and Porosity in Thin Film Deposition
    Industrial & Engineering Chemistry Research, 2009
    Co-Authors: Gangshi Hu, Gerassimos Orkoulas, Panagiotis D Christofides
    Abstract:

    This work focuses on stochastic modeling and simultaneous regulation of surface roughness and porosity for a porous thin Film deposition Process modeled via kinetic Monte Carlo (kMC) simulation on a triangular lattice. The microscopic model of the thin Film Growth Process includes adsorption and migration Processes. Vacancies and overhangs are allowed inside the Film for the purpose of modeling thin Film porosity. The definition of the surface height profile is first introduced for a porous thin Film deposition taking place in a triangular lattice. The dynamics of surface height of the thin Film are described by an Edwards-Wilkinson (EW) type equation, which is a second-order linear stochastic partial differential equation (PDE). The root-mean-square (RMS) surface roughness is chosen as one of the controlled variables. Subsequently, an appropriate definition of Film site occupancy ratio (SOR) is introduced to represent the extent of porosity inside the Film and is chosen as the second to-be-controlled var...

  • Simultaneous regulation of Film thickness, surface roughness and porosity in a multiscale thin Film Growth Process
    Proceedings of the 48h IEEE Conference on Decision and Control (CDC) held jointly with 2009 28th Chinese Control Conference, 2009
    Co-Authors: Gangshi Hu, Gerassimos Orkoulas, Xinyu Zhang, Panagiotis D Christofides
    Abstract:

    This work focuses on simultaneous regulation of Film thickness, surface roughness and porosity in a multiscale model of a thin Film Growth Process using the inlet precursor concentration as the manipulated input. Specifically, a continuous macroscopic partial differential equation model is used to describe the dynamics of the gas phase. The thin Film Growth Process is modeled via a microscopic kinetic Monte Carlo simulation model on a triangular lattice with vacancies and overhangs allowed to develop inside the Film. Closed-form dynamic models of thin Film surface profile and porosity are developed and used as the basis for the design of a model predictive control algorithm to simultaneously regulate Film thickness, surface roughness and Film porosity. Simulation results demonstrate the applicability and effectiveness of the proposed modeling and control approach by applying the proposed controller to the multiscale model.

Luis A. Ricardez-sandoval - One of the best experts on this subject based on the ideXlab platform.

  • Optimization and control of a thin Film Growth Process: A hybrid first principles/artificial neural network based multiscale modelling approach
    Computers & Chemical Engineering, 2018
    Co-Authors: Donovan Chaffart, Luis A. Ricardez-sandoval
    Abstract:

    Abstract This work details the construction and evaluation of a low computational cost hybrid multiscale thin Film deposition model that couples artificial neural networks (ANNs) with a mechanistic (first-principles) multiscale model. The multiscale model combines continuum differential equations, which describe the transport of the precursor gas phase, with a stochastic partial differential equation (SPDE) that predicts the evolution of the thin Film surface. In order to allow the SPDE to accurately predict the thin Film Growth over a range of system parameters, an ANN is developed and trained to predict the values of the SPDE coefficients. The fully-assembled hybrid multiscale model is validated through comparison against a kinetic Monte Carlo-based thin Film multiscale model. The model is subsequently applied to a series of optimization and control studies to test its performance under different scenarios. These studies illustrate the computational efficiency of the proposed hybrid multiscale model for optimization and control applications.

  • Robust multivariable estimation and control in an epitaxial thin Film Growth Process under uncertainty
    Journal of Process Control, 2015
    Co-Authors: Shabnam Rasoulian, Luis A. Ricardez-sandoval
    Abstract:

    Abstract This study presents a multivariable robust estimator that predicts the controlled outputs in a thin Film Growth Process for online applications. The evolution of the epitaxial Growth Process on a substrate is modeled based on a multiscale approach, coupling a continuum gas phase model and a kinetic Monte Carlo (KMC) model that describes the evolution of the thin Film surface. In the estimator, the issue of computationally intensive KMC simulations is circumvented by developing reduced-order models that are identified offline based on data obtained from the multiscale model. This approach significantly reduces the simulation time over KMC and makes the online control and optimization feasible. The estimator evaluates the surface roughness and Growth rate based on the substrate temperature and the bulk precursor mole fraction during the Growth Process. To provide robust estimations, the estimator is designed to evaluate the upper and lower bounds on the outputs under model parameter uncertainties. To assess the uncertainty propagation into the system's outputs, power series expansion (PSE) is employed in the presence of distributional parametric uncertainties. The sensitivities of the outputs with respect to the uncertain parameters are assessed offline at different substrate temperatures and bulk precursor mole fractions. Accordingly, upper and lower bounds on the outputs are determined at a specific confidence level and employed to identify a reduced-order model for online applications. To assess the efficiency of the estimator, proportional integral (PI) controllers are coupled with the estimator to control surface roughness and Growth rate while manipulating the substrate temperature and the bulk precursor mole fraction, respectively. The robust control of the Process under parameter uncertainties is investigated using the bounds estimated on the controlled outputs.