Abstract: A system and method for controlling a critical process variable, such as the temperature of one or more temperature control units for cluster tools in a semiconductor fabrication facility, uses dual interrelated PID) algorithms for interrelated but at times separate control of heating capabilities. The temperature control units operate with high power efficiency, because no heating energy is expended during cooling and non-transition modes. When approaching a temperature threshold, however, the heating algorithm is reinstated just long enough to provide minimum undershoot and enabling precise, low per consuming, steady state control at ±0.1° C., minimizing undershoot and enabling precise steady state control at ±0.1° C.

Abstract: A system and method for controlling a critical process variable, such as the temperature of one or more temperature control units for cluster tools in a semiconductor fabrication facility, uses dual interrelated PR) algorithms for interrelated but at times separate control of heating capabilities. The temperature control units operate with high power efficiency, because no heating energy is expended during cooling and non-transition modes. When approaching a temperature threshold, however, the heating algorithm is reinstated just long enough to provide minimum undershoot and enabling precise, low per consuming, steady state control at ±0.1° C., minimizing undershoot and enabling precise steady state control at ±0.1° C.