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Abstract The class of continuous film-forming reactors used in the diffusion limited stages of polycondensation processes can be modeled approximately as a finite thickness slab in which reaction and simultaneous diffusion of the volatile... more
Abstract The class of continuous film-forming reactors used in the diffusion limited stages of polycondensation processes can be modeled approximately as a finite thickness slab in which reaction and simultaneous diffusion of the volatile by-product toward the free surface must be coupled with a step to account for periodic mixing of the film. Solutions of the resulting partial differential equation model are shown to correlate adequately by a single algebraic equation over a wide range of values of the three independent parameters. Rearrangement of this “ mixing film model” into an “efficiency factor” yields an expression for the importance of diffusional resistances in the reactor.
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... Edgar 1980), and it reduces the optimization problem to a single parameter search. (In any case, if two or more non-zero closed-loop poles are desired, the tech-nique can easily be extended.) Now V becomes (17) and eqn. (16) is... more
... Edgar 1980), and it reduces the optimization problem to a single parameter search. (In any case, if two or more non-zero closed-loop poles are desired, the tech-nique can easily be extended.) Now V becomes (17) and eqn. (16) is written or (18) Page 8. 1138 PE McDermott ...
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Iii previous work by Sturtevant et al [1994] it was shown how the use of scatterometry data obtained in real time during the post-expose bake (PEB) step of the photolithography process can improve critical dimension (CD) control. However,... more
Iii previous work by Sturtevant et al [1994] it was shown how the use of scatterometry data obtained in real time during the post-expose bake (PEB) step of the photolithography process can improve critical dimension (CD) control. However, it is not obvious that the ad hoc methodology utilized during these experiments conducted at IBM, is the best way to use this valuable information. This paper focuses on the development of more rigorous methods that can incorporate scatterometry data in on-line prediction of the bake time necessary to achieve the target CD. First, a brief description of the system and required tools is given. Then, a model that can relate the measured intensity and the time the wafer has been baked (referred to hereafter as the bake time) is introduced. Then, two theoretical methods that can utilize this model to calculate the bake end point are described. Finally, these two methods are applied to the analysis ofadditional data collected at IBM and operation oftbe complete end point control system is emulated to the extent that is possible. Keywords: end-point detection, process control, deep-UV lithography, scatterometry, post-exposure bake process
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ABSTRACT
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Richard H. Heist (with T.O. Olsen and H.M. Saltsburg) is a contributing author, Unsteady State Heat Transfer in a Sphere , pp. 5967 and Ion Exchange Experiment , pp. 85-96
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The performance of a multivariable self-tuning controller (STC) has been evaluated via a simulation study of two distillation columns. The self-tuner is based on Koivo's approach (1980), but it can be applied to systems which contain... more
The performance of a multivariable self-tuning controller (STC) has been evaluated via a simulation study of two distillation columns. The self-tuner is based on Koivo's approach (1980), but it can be applied to systems which contain multiple time delays and/or multirate sampling. The effects of important design parameters are illustrated by the simulation results.
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Abstract The multivariable self-tuning controllers of Chien et al. incorporate a Smith predictor-type of time delay compensation (STC-TDC). These are applied to dual composition control of a pilot-scale multicomponent distillation... more
Abstract The multivariable self-tuning controllers of Chien et al. incorporate a Smith predictor-type of time delay compensation (STC-TDC). These are applied to dual composition control of a pilot-scale multicomponent distillation process. Both versions of the STC-TDC, i.e., with and without decoupling, are compared with a standard dual-loop PI controller and are seen to provide excellent control in the face of significant process interactions and nonlinearities.
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This paper presents a method of interactive or real-time predictive control which can be implemented without a stored program computer. By restricting the process dy namic model to a second-order-plus-dead-time format, a configuration... more
This paper presents a method of interactive or real-time predictive control which can be implemented without a stored program computer. By restricting the process dy namic model to a second-order-plus-dead-time format, a configuration which is satisfactory for many chemical or petroleum processing systems, a time-optimal controller can be built entirely on a small analog/hybrid computer. For set-point changes, the controller utilizes an analog model of the process to search out the predicted optimum input switching sequence and continuously maintains the process on the time-optimal trajectory. Because of the predictive nature of the method there is no necessity to include the time-delay term in the high-speed model; the predicted switches in the process input are simply ad vanced in time by the amount of the time-delay.
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... Current interest in self-tuning control systems was largely stimulated by the development of the self-tuning regulator (STR) by Astrorn and Wittenmark (1973 ...
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... t)= T~(O,t)= T0(t)=unknown c(O,t)10 for any t O (4) at z= 1 T,(1,t)= TF(t) for any taO (5) STEADY ... N) The matnces formed from the coefficients of these equations A1, A2, A3 contain time-independent ele-ments which are computed... more
... t)= T~(O,t)= T0(t)=unknown c(O,t)10 for any t O (4) at z= 1 T,(1,t)= TF(t) for any taO (5) STEADY ... N) The matnces formed from the coefficients of these equations A1, A2, A3 contain time-independent ele-ments which are computed according to the method of Villadsen and ...
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Page 1. POLE PLACEMENT SELF-TUNING CONTROL OF UNSTABLE NONMINIMUM PHASE SYSTEMS PE McDermott and DA Hellichamp Department of Chemical and Nuclear Engineering University of California Santa Barbara, CA 93106 USA ...
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Research Interests: Computer Science, Chemistry, Social Media, Icon, Citation, and 3 moreAltmetrics, ICON, and Frequency Domain
Parameter estimation methods often assume that no a priori knowledge of the plant is available. Often, as in the case of a stiff plant, qualitative or heuristic information is readily inferred. This paper presents a decentralized method... more
Parameter estimation methods often assume that no a priori knowledge of the plant is available. Often, as in the case of a stiff plant, qualitative or heuristic information is readily inferred. This paper presents a decentralized method of parameter estimation for stiff systems that utilizes available knowledge of the relationships among the response modes of this type of plant, in
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Research Interests: Engineering, Chemical Engineering, Biomedical Engineering, Agricultural Biotechnology, Bioprocess Engineering, and 12 moreBioreactor, Mass production, Biomass production, Industrial and production engineering, Nonlinear system, Simulation Study, System modeling, Nonlinear State Estimation, Process Model, Adaptive Optimization, optimal algorithm, and Dilution
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Page 1. Chem. Eny. Commun. Vol. 31 pp. 263-287 0 1984 Gordon and Breach, Science Publishers, Inc. 0098-6445/84/3 101 -0263$25.00/0 and OPA Lld. Printed in the USA EIGENVALUE SPECTRA AND MODAL CONTRIBUTIONS FOR COUNTERFLOW REACTOR ...
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Hierarchical computer networks are useful in process control because they decentralize processing and thereby result in easier system development and greater fault tolerance. This type of network can be characterized by the flow of jobs... more
Hierarchical computer networks are useful in process control because they decentralize processing and thereby result in easier system development and greater fault tolerance. This type of network can be characterized by the flow of jobs to and from a single node computer. In this work a three-level hierarchy with a single node computer has been simu lated using a dual minicomputer system. One of the machines is used to simulate the node computer, the other machine to represent the low-level computers and the overall master computer. The simulation allows the user to maintain control over all key network parameters and to adjust them dynamically if desired. The output data permits the detailed monitoring of the performance of the net work. Some typical operating results are presented which illustrate the use of the approach to evaluate alternate job-scheduling strategies or to optimize a single scheduling algorithm.
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A method is presented to apply the gain identification procedures developed in a companion paper to a control system. The method employs a small identification tank which follows the control tank; the identification tank is perturbed to... more
A method is presented to apply the gain identification procedures developed in a companion paper to a control system. The method employs a small identification tank which follows the control tank; the identification tank is perturbed to estimate the gain of the process (controlled tank system). The effects of load changes on the identification system are minimized by this approach.The results of analog and digital computer simulations of this adaptive process are given. Both a general system with linear change in gain and a pH control system with a step change in concentration of the buffer species are studied. Process gain changes up to 20:1 are introduced.It is concluded that an adaptive control system of this type can be designed to maintain good control characteristics in a process experiencing wide gain variation. Criteria are presented to aid in the design of an adequate identifier.
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... linewidih near the bom of the feature [161. The parmeterestthese tests was performed in an off-line fashion, ulang a situaon in which initial estimes were obtained before the beginnng of the nm by developing three wafers with differnt... more
... linewidih near the bom of the feature [161. The parmeterestthese tests was performed in an off-line fashion, ulang a situaon in which initial estimes were obtained before the beginnng of the nm by developing three wafers with differnt development times and fittng the ROM to the ...
Research Interests: Engineering, Computer Science, Adaptive Control, Computer Aided Manufacturing, Membrane Technology, and 11 moreParameter estimation, Photolithography, Lithography, Chemical Industry, Nonlinear system, Simulation Study, Nonlinear and Adaptive Control, Nonlinear Model, Development Time, Optimization of Chemical Processes, and Reduced Order Macro model
A closed-loop adaptive control technique for photolithography is proposed and evaluated. In this strategy, development time is manipulated in order to keep the output critical dimension at a desired value, despite the disruptive effects... more
A closed-loop adaptive control technique for photolithography is proposed and evaluated. In this strategy, development time is manipulated in order to keep the output critical dimension at a desired value, despite the disruptive effects of unmeasured process disturbances. The adaptive control strategy incorporates a three parameter reduced-order model of the photolithography process, a parameter estimator, and a nonlinear model-inversion controller. Simulation studies show that the adaptive controller is able to reject the detrimental effects of process disturbances and bring the critical dimension back to its desired value. In the simulations, PROLITH was used to represent the real lithography process.