Nonlinear control strategy for thermal budget in spike rapid thermal processing systems based on Wiener model

Abstract

ABSTRACTThe spike‐shaped temperature profile in thermal treatments is widely used in semiconductor manufacturing for providing precise thermal budget. This thermal budget control issue gets more crucial as the technology node progressively shrinks. Therefore, rapid thermal processing (RTP) with spike‐shaped temperature profile, such as spike annealing, has the ability to meet this requirement. With its exceptionally stringent performance requirements (e.g. high temperature ramp‐up/down rate and high temperature uniformity), temperature control in RTP systems is a challenging task. Our previous work proposed a methodology of control system design which can precisely target the thermal budget indices. The major problem in that work is that a linear model of the RTP system is assumed, but the dynamics of RTP system is, in fact, nonlinear in nature. In this study, we extend the previous work by considering the nonlinearity of the RTP system. First, a nonlinear Wiener model, instead of linear model, is used to represent the RTP system. For this purpose, a simple noniterative algorithm for the identification of Wiener model is proposed. Then, a simple nonlinear control strategy based on the Wiener model is developed for providing precise thermal budget. Simulation results have shown that the proposed method performs well in spike RTP systems. © 2011 Curtin University of Technology and John Wiley & Sons, Ltd.