Non-contact Temperature Measurement of Semitransparent Silicon Wafers

Silicon wafers become semitransparent at room temperature and at wavelengths more than 1.1 mum. Silicon wafers with an oxide film layer are also semitransparent because the extinction coefficient of the film optical constants is negligible at visible and infrared wavelengths. We experimentally studied optical properties such as emissivity, reflectivity and transmissivity of silicon wafers with and without oxide films to devise a new non-contact method of temperature measurement that is applicable to semitransparent silicon wafers near room temperature. The proposed method which is constituted from two blackbodies and p-polarized optical components showed the accuracy of plusmn1 K in the temperature range from 313 to 343 K using a radiometer with an InSb sensor at a wavelength of 4.7 plusmn0.1 (am for silicon wafers with low resistivity, irrespective of changes of oxide layer thickness. The method is, however, unable to apply to the measurement near room temperature for silicon wafers with resistivity over 0.1 Omegacm because of their emissivities are extremely small