Traceable temperature calibrations of radiation thermometers for rapid thermal processing

Lightpipe radiation thermometers (LPRTs) have been successfully calibrated at NIST for rapid thermal processing (RTP) applications using a sodium heat-pipe blackbody (Na-HPBB) between 700°C and 900°C with an uncertainty of about 0.3°C (k=1) traceable to the International Temperature Scale of 1990 (ITS-90). Using appropriate effective emissivity models, LPRTs have been used to determine the wafer temperature in the NIST RTP Test Bed with an uncertainty of 3.5°C. With the aid of a thin-film thermocouple wafer, the LPRT can measure the wafer temperature in the NIST RTP Test Bed with an uncertainty of 2.1°C. In RTP reactors where optical access is available, spot-type radiation thermometers (STRTs) become an attractive technique for temperature measurement. From 700°C to 900°C, STRTs can be calibrated against the Na-HPBB with an uncertainty of about 1.1°C. Cable-less LPRTs (CLRTs) offer a decisive advantage to greater traceability than traditional LPRTs. Application of CLRTs eliminates 2.0°C or more uncertainty from the calibration scheme. The Na-HPBB source and the calibration procedures and uncertainties will be discussed. Calibrating radiation thermometers using the NIST Na-HPBB offers traceability to the ITS-90, decreases temperature measurement uncertainties, and improves temperature accuracy.