The Effect of Thin Dielectric Films on the Accuracy of Pyrometric Temperature Measurement

Pyrometers are used to measure wafer temperature in rapid thermal processors. This paper focuses on the effect of thin dielectric films on the accuracy of pyrometric temperature measurement. The thin films affect the emissivity of the wafer, which in turn affects the radiation emitted by the wafer. Wafers with different oxide thicknesses were monitored by both pyrometer and thermocouple. Temperature errors of the order of 10°C to 50°C were found for wafers of differing oxide thicknesses. The chamber reflectivity was found to be an important factor in determining the ‘effective’ emissivity of the wafer. Pyrometer recalibration is necessary to accurately measure wafer temperature.