Closed-loop adaptive control for rapid thermal processing

An important objective of the feedback control for a rapid thermal processing (RTP) system for a semiconductor wafer is to maintain a uniform temperature of the wafer as it follows a given temperature trajectory. In this paper an adaptive control algorithm is developed using a combination of feedback linearization and a new, nonlinear observer for estimating the exogenous disturbance parameters. The dynamic model, exploiting the circular symmetry of the physical configuration, uses coefficients of a Bessel function expansion as the state variables. An interesting separation property of the control algorithm is proved. A simulation study, using process parameters derived from experimental data obtained from an actual RTP system, gives excellent results