RESOLUTION OF SILICON-WAFER TEMPERATURE-MEASUREMENT BY IN-SITU ELLIPSOMETRY IN A RAPID THERMAL PROCESSOR

The application of ellipsometry as a technique for in situ silicon wafer temperature measurement in a rapid thermal processing environment was investigated. This technique is based on the ellipsometric measurement of the refractive index of silicon, and then the determination of the temperature from the known temperature dependence of the refractive index. An algorithm was developed which enables the determination of the resolution limits of this technique. Within the temperature range from 0 to 1100-degrees-C, a worst-case temperature error of +/- 10-degrees-C can be expected for an ellipsometer operating at a wavelength of 6328 angstrom and resolving 0.01-degrees in the measured parameters psi and DELTA, and in the angle of incidence phi. For an ellipsometer operating at a wavelength of 4133 angstrom, the maximum error improves to within +/- 1.4-degrees-C, for the temperature range investigated from 0 to 700-degrees-C.