Calibration of Lightpipe Radiation Thermometers in a RTP Tool at 1000 Degrees Celsius
Vincent P. Scheuerman, K Kreider, C Meyer, D Dewitt
We are developing an instrumented calibration wafer for radiometric temperature measurements in rapid thermal processing (RTP) that uses Pt/Pd wire and noble metal thin-film thermocouples that are welded to thin-film pads of Pt. The Pt/Pd wire thermocouples determine the weld junction temperature within a standard uncertainty of 0.1 degrees C at 1000 degrees C. Thin films of noble metals including Pd, Pt, Rh, Ru, and Ir reach from the wire junction to locations near the radiometric target to establish the surface temperature of the wafer at the target. These thin-film thermocouples (TFTC's) are calibrated at NIST and have a standard uncertainty of 0.3 degrees C for differential temperature measurements of up to 10 degrees C at temperatures up to 1000 degrees C on the wafer. In the past we have reported on TFTCs that were useful up to 900 degrees C, but problems of SiO(2) electrical conductivity, coalescence of the thin films, and oxidation of the films have precluded their use at 1000 degrees C. We now report solutions to those problems while maintaining a standard uncertainty of 0.4 degrees C for the surface temperature measurement. We have found that it was necessary to increase the thickness of the thermal SiO(2) to 690 nm from the 310 nm previously used. In order to improve the stability of the Pt against coalescence and pore growth, we have made the traces thicker (>1 um) and covered them with SiO(2). We can fabricate the TFTCs from the more refractory noble metals (Rh, Ru, and Ir) but an increase in the temperature measurement uncertainty is caused by the smaller Seebeck coefficients of these combinations cause an increase in the temperature measurement uncertainty because of their smaller Seebeck coefficients. We use the NIST Rh/Pt thin-film thermocouple wafer with Pt/Pd wire thermocouples in the NIST RTP test bed to illustrate a method of in situ calibration. The 0.4 degrees C standard uncertainty combined with the uncertainty of temperature difference between the locations of the thermocouple junction and radiometric measurements led to a calibration uncertainty of 2 degrees C for RTP light pipe radiation thermometers in the range of 700 degrees C and 1000 degrees C.
International Symposium on Advanced Thermal Processing of Semiconductors
, Kreider, K.
, Meyer, C.
and Dewitt, D.
Calibration of Lightpipe Radiation Thermometers in a RTP Tool at 1000 Degrees Celsius, International Symposium on Advanced Thermal Processing of Semiconductors, San Francisco, CA
(Accessed May 29, 2023)