Fuzzy control of temperature in a semiconductor processing furnace

The ability to control temperature in semiconductor processing furnaces is critical to the manufacturing of semiconductor devices. In this paper, a fuzzy PI controller is described that takes into account some of the unique characteristics of such a furnace. Entries in the rule base are used to prevent integrator windup and a fuzzy gain scheduler allows the controller to be tuned once and used over the whole operating temperature range of the system. Substantial improvements are shown for settling times following both large and small step changes in reference setpoint