Many Rapid Thermal Processing (RTP) tools are currently monitored and controlled with lightpipe radiometers (LPRTs), which have been limited to measuring temperatures above 500 C because of the low signal level below 500 C. New commercial LPRTs couple the optical detector directly to the sapphire lightpipe, eliminating the signal loss from optical cables and allowing measurement of wafer temperatures to below 300 C. We present the results of calibrating a cable-less lightpipe radiation thermometer (CLRT) against our NIST thin-film thermocouple (TFTC) calibration wafer from 315 C to 700 C in our NIST RTP test bed. Below 550 C, light leakage from the heating lamps of the RTP tool introduced a significant error in the LPRT readings. By measuring the transient response of the LPRTs following rapid energizing of the heating lamps, we were able to differentiate between the radiance of the wafer and ambient chamber light. This allowed us to correct for the ambient chamber light from the radiance of the wafer.
Proceedings Title: 12th IEEE International Conference on Advanced Thermal Processing of Semiconductors
Conference Dates: September 28-30, 2004
Conference Location: Portland, OR
Pub Type: Conferences
calibration, lightpipe, pyrometry, wafer temperature