Temperature Measurement of Silicon Wafers by Transmissivity Sensing

Transmissivity of a silicon wafer strongly depends on temperature. Using this characteristic of the silicon wafer, we studied two non-contact methods of temperature measurement for silicon wafers in the temperature range from 300 K to 1000 K. The one is the use of temperature dependence of transmissivity, and the other is the use of optical absorption edge wavelength. Both methods are pursued from the view points of wavelength (900~1750 nm), polarization (p-and s-polarized) and direction (normal to 80deg) for specimens with different resistivity (0.01 Omegacm~2700 Omegacm). We obtained some promising knowledge for application to temperature measurement of silicon wafers. For example, for the former method, the use of longer wavelengths over 1500 nm is suitable in the high temperature range over 600 K, and the use of shorter wavelengths less than 1200 nm is appropriate in the low temperature range below 600 K. On the other hand, for the latter method using optical absorption edge wavelength is effective in the temperature range from room temperature to high temperature of 1000 K. In this paper, experimental results and discussions are quantitatively described and considered in detail