One aspect of the present invention relates to a system for determining and controlling a microloading effect in order to achieve desired feature depth on a wafer. The extraction module includes a particulate removal unit for removing pollutants from the extracted combustion gas and a heat exchanger in downstream fluid communication with the particulate removal unit for cooling the extracted combustion gas. In partial-screen display, the signal processing circuit interrupts a signal tapped off from a predetermined stage of the shift register.