An emissivity-invariant condition of silicon wafers and its application to radiation thermometry

The emissivity behavior of a silicon wafer is simulated using a simple modeling of the spectral, directional and polarization characteristics of thermal radiation. This study reveals that the p-polarized spectral emissivity of the silicon wafer at a specified direction remains constant. Then, subsequent experiments confirmed the simulated results that the p-polarized emissivity of silicon wafers is maintained to be 0.83 at an angle of 55.4deg and a wavelength of 0.9 mum in spite of wide variations in oxide film thickness from 0 to 950 nm, temperature over 900 K as well as resistivity from 0.01 to 2000 Omegacm relevant to impurity concentrations doped into the silicon wafer. The overall extended uncertainty (k =2) of the temperature measurement is estimated to be 3.82 K over 900 K at the moment. This result is expected to enable significantly more accurate in situ radiation thermometry of silicon wafers in real manufacturing processes.