Drawdown-Effect of Lightpipes in Silicon Wafer Surface Temperature Measurements

Lightpipe radiation thermometers (LPRTs) have been widely used for temperature measurement in the semiconductor industries. According to the International Technology Roadmap for Semiconductors 2004 (ITRS), temperatures for semiconductor wafer processing should be measurable to within an uncertainty of ± 1.5°C at 1,000 °C with temperature calibration traceable to ITS (international temperature standard)-90. To achieve this uncertainty, there are several issues associated with LPRTs to be resolved. The “draw-down effect” is the one that will be examined in this paper. We discuss this effect both experimentally and numerically in the temperature range of 500°C to 900°C.