Temperature measurement and control are key issues in many technologically important areas of semiconductor processing, including rapid thermal annealing, molecular‐beam epitaxy, and plasma processing. As a result, the development of accurate techniques for the characterization of thermal cycles is a problem of great practical interest.
In this study, the total emissivity of specimens of GaAs was determined using a technique which combines isothermal electron‐beam heating with a temperature measurement method which exploits the temperature dependence of the band gap of GaAs. Emission spectra from the GaAs specimens were recorded for a range of heating power densities. These spectra display a maximum near the semiconductor absorption edge, because the blackbody radiation rises with increasing wavelength but the spectral emissivity decreases rapidly once the photon energy falls below the band gap.
The temperature was determined by fitting the Planck radiation function to the high‐energy side of the maximum. This allowed a self‐consistent determination of the temperature dependence of the position of the absorption edge.
The results were used to calibrate a second set of experiments in which a corresponding set of reflection spectra were recorded. The reflection spectra exhibit a large change in reflectivity at the absorption edge, because light starts being reflected from the back surface of the wafer as well as from the front when it becomes transparent.
Timans, P.J., 1992. The experimental determination of the temperature dependence of the total emissivity of GaAs using a new temperature measurement technique. Journal of applied physics, 72(2), pp.660-670.
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Categories: Semiconductor & Process Monitoring