Institute for Systems Research Technical Reports
Permanent URI for this collectionhttp://hdl.handle.net/1903/4376
This archive contains a collection of reports generated by the faculty and students of the Institute for Systems Research (ISR), a permanent, interdisciplinary research unit in the A. James Clark School of Engineering at the University of Maryland. ISR-based projects are conducted through partnerships with industry and government, bringing together faculty and students from multiple academic departments and colleges across the university.
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Item A Comparative Study of Reactor Designs for the Production of Graded Films with Applications to Combinatorial CVD(2007-10-24) Sreenivasan, Ramaswamy; Adomaitis, Raymond A.Segmented CVD reactor designs enabling spatial control of across-wafer gas phase composition were evaluated for depositing graded films suitable for combinatorial studies. Specifically two reactor designs were constructed and evaluated with experiments and response surface model (RSM) based analysis to quantify the reactor performance in terms of film thickness uniformity, sensitivity to adjustable reactor operating conditions, range of thickness over which uniformity could be achieved and each reactor’s ability to control the thickness gradient across the wafer surface. Design features distinguishing the two reactor systems and their influence on gradient control versus deposition rate performance are summarized. RS models relating wafer state properties to process recipes are shown to be effective tools to quantify, qualify and compare different reactor designs.Item Influence of Gas Composition on Wafer Temperature Control in a Tungsten Chemical Vapor Deposition Reactor(2000) Chang, Hsiao-Yung; Adomaitis, Raymond A.; Kidder, John N., Jr.; Rubloff, Gary W.; ISRExperimental measurements of wafer temperature in a single-wafer,lamp-heated CVD system were used to study the wafer temperature responseto gas composition. A physically based simulation procedure for theprocess gas and wafer temperature was developed in which a subset ofparameter values were estimated using a nonlinear, iterative parameteridentification method, producing a validated model with true predictivecapabilities.With process heating lamp power held constant, wafertemperature variations of up to 160 degrees K were observed by varying feed gasH_2/N_2 ratio. Heat transfer between the wafer and susceptor wasstudied by shifting the instrumented wafer off the susceptor axis,exposing a portion of the wafer backside to the chamber floor. Modelpredictions and experimental observations both demonstrated that the gasvelocity field had little influence on the observed wafer and predictedgas temperatures.
Item Model Reduction for a Tungsten Chemical Vapor Deposition System(1998) Chang, Hsiao-Yung; Adomaitis, Raymond A.; ISRA model of a tungsten chemical vapor deposition (CVD) system isdeveloped to study the CVD system thermal dynamics and wafer temperaturenonuniformities during a processing cycle. We develop a model for heattransfer in the system's wafer/susceptor/guard ring assembly and discretizethe modeling equation with a multiple-grid, nonlinear collocation technique.This weighted residual method is based on the assumption that the system'sdynamics are governed by a small number of modes and that the remaining modesare slaved to these slow modes. Our numerical technique produces a model thatis effectively reduced in its dynamical dimension, while retaining theresolution required for the wafer assembly model. The numerical techniqueis implemented with only moderately more effort than the traditional collocationor pseudospectral techniques. Furthermore, by formulating the technique in termsof a collocation procedure, the relationship between temperature measurementsmade on the wafer and the simulator results produced with the reduced-ordermodel remain clear.Item Analysis of Heat Transfer in a Chemical Vapor Deposition Reactor: An Eigenfunction Expansion Solution Approach(1997) Chang, Hsiao-Yung; Adomaitis, Raymond A.; Adomaitis, Raymond A.; ISRA numerical solution procedure combining several weighted residual methods and based on global trial function expansion is developed to solve a model for the steady state gas flow field and temperature distribution in a low-pressure chemical vapor deposition reactor. The enthalpy flux across the wafer/gas boundary is calculated explicitly and is found to vary significantly as a function of wafer position. An average heat transfer coefficient is estimated numerically and is compared to typical radiative heat transfer rates in the system. The convergence properties of the discretization method developed also are discussed.