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Title: Application of iterative feedback tuning
Keywords: resist thickness, IFT, relay auto-tuning
Issue Date: 28-Oct-2003
Citation: DENG JIEWEN (2003-10-28). Application of iterative feedback tuning. ScholarBank@NUS Repository.
Abstract: Lithography technology has been one of the key enablers and drivers for the semiconductorindustry for the past several decades. Improvements in lithography are responsible for roughly half of the improvement in cost per function in integrated circuit(IC) technology. In this thesis, in-situ process monitoring and Iterative Feedback Tuning(IFT) are used to control the resist thickness uniformity across the wafer, as well as to improve the convergence time to a specified reference thickness. Using an array of in-situ thickness sensors to measure the thickness, and the IFT algorithm to update the PI(Proportional Integral) controller, a real-time control strategy is implementedto control the resist thickness during softbake. An average of 19 times improvement in the resist thickness uniformity is achieved and the time to convergence is reduced significantly. Also, the thesis investigated the application of IFT to auto-tune a PID controller during the relay experiment to give specified phase margin and bandwidth. Goodtuning performance according to the specified phase margin and bandwidth can be obtained and the limitation of the standard relay auto-tuning technique using a version of the Ziegler-Nichols formula can be eliminated.
Appears in Collections:Master's Theses (Open)

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