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MIT Electrical Engineering and Computer Science
EECS Event |
Tuesday, October 3, 2000
4:00 PM (reception following)
Room 35-225
LIDS Colloquium
Abstract
This talk will address the modeling, control, and optimization issues involved in thermal processing and thin film deposition. The modeling and control design issues will be illustrated based on our experiences with RTP (rapid thermal processing) for silicon wafers, RF diode sputtering deposition of GMR (giant magneto-resistive) materials, and MBE (molecular beam epitaxy) for III-V nanoelectronic devices.
The common theme that links these three different processes is that they all operate under closed-loop control. It is our experience that the best models for control design borrow heavily from the physics of the process, but how the models are used for specific application depends on the performance goals. In some cases (e.g., RTP), the closed-loop control depends entirely on having very good physical models of the system. For sputter deposition of GMR, a carefull sensitivity analysis identified the primary sources of uncertainty, and lead to significant repeatability improvements. For MBE, a single species KMC model of island (layer-to-layer) growth was used to devise a control strategy for controlling morphology using a RHEED sensor.
Model reduction and uncertainty modeling will also be discussed in the more general context of controling the atomic assemby or materials or manipulating quantum mechanical states. Modeling for control on this scale remains an open research issue.