Radiation thermometry of silicon wafers based on emissivity-invariant condition.

An emissivity-invariant condition for a silicon wafer was determined by simulation modeling and it was confirmed experimentally. The p-polarized spectral emissivity at a wavelength of 900 nm and at temperatures over 900 K was constant at 0.83 at an angle of about 55.4° irrespective of large variations in the oxide layer thickness and the resistivity due to the different impurity doping concentrations of the silicon wafer. The expanded uncertainty, U(c) = ku(c) (k = 2), of the temperature measurement is estimated to be 4.9 K. This result is expected to significantly enhance the accuracy of radiometric temperature measurements of silicon wafers in actual manufacturing processes.