Hybrid feedforward and feedback control of wafer temperature in RTP using genetic algorithm and fuzzy logic

This paper proposes a hybrid controller design method using the genetic algorithm and the fuzzy logic to control the wafer temperature in RTP system. First, we design feedforward static controller to provide the control powers of the lamps for the given steady state temperature. Second, the feedforward dynamic controller is designed for the additional control powers to achieve a given transient response. These feedforward controllers are implemented by using the fuzzy logic to act as global nonlinear controller over a wide range of operating points. The parameters of these controllers are optimized by using genetic algorithm so that it can be used when the mathematical model is not available. In addition. A feedback controller is introduced to compensate the feedforward controllers when there exist disturbances and modeling errors. The gain of feedback controller is also obtained by means of genetic algorithm. Through simulations, we verify that the proposed control system can give a satisfactory performance