ITR: Feedback Control of Thin Film Microstructure Using Multiscale Distributed Models

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Research:The objective of this research program is to develop a comprehensive theoretical, computational and experimental program for nonlinear model-based feedback control of film microstructure in chemical vapor deposition of thin films using multi-scale distributed models. Distributed control theory for multi-scale distributed models will be developed and employed to produce novel analytical feedback controller and estimator designs that enforce the desired stability, performance and robustness specifications in the multi-scale closed-loop system and achieve thin film microstructure with desired characteristics (e.g., reduced roughness). The motivation for this work is provided by: a) the increasing need for control of thin film microstructure, b) the high-sensitivity of thin film microstructure with respect to arbitrary variations in operating conditions, and c) the lack of systematic and comprehensive framework for feedback control that can shape thin film microstructureon-line.To realize the desired objective, the proposed research will focus on the following projects:1. The development of computationally efficient and accurate algorithms for order reduction of multi-scale distributed models.2. The design of multi-scale reduced-order estimators and nonlinear feedback controllers that can shape material microstructure in a desirable way.3. The integration of on-line diagnostic techniques with multi-scale distributed models and the study of fundamental control theoretic issues.4. The application of the control algorithms to simulated thin film growth problems.5. The development and experimental application of a real-time integrated measurement/control system to a lab-scale plasma-enhanced CVD process at UCLA to control thin film microstructure and spatial variations.Impact:The research will provide a fundamental understanding of the nature of the model reduction, optimization and control problems for multi-scale distributed systems, develop concrete control algorithms that can be readily implemented in practice, illustrate the application of the control methods and derive tuning guidelines for the implementation of the controllers. The development of a software package and the collaboration with companies will be the means for transferring the results of the research to the industrial sector. The integration of the research into education would benefit educators teaching advanced-level classes in process control and semiconductor manufacturing. The new control algorithms are expected to lead to significant advances in our ability to shape, on-line, material microstructure in the chemical vapor deposition of thin films. Information Technology (IT) serves both as a major enabler and beneficiary of the proposed research. On the one hand, IT developments, such as advances in high-confidence computing, sensing, data processing, and software systems, provide an indispensable mechanism for realizing the project goals. In turn, the research has the potential to further advance IT developments through improved semiconductor manufacturing technologies that represent an integral part of modern-day IT infrastructure.