The temperature of silicon wafers may be inferred by measuring the transmission of infrared light through the wafers. In this paper, the fundamental absorption mechanisms in silicon at 1.30 and 1.55 μm have been investigated in the temperature range of 500-800°C. For lightly doped wafers in this temperature range, the absorption at 1.55 pm is by free carriers, and that at 1.30 μm is predominantly by bandgap absorption. The effect of heavy substrate doping on infrared absorption at elevated temperature has also been studied, and it was found that doping has little effect below levels of 7 × 1017 cm-3, Above that level the temperature dependence of free carrier absorption strongly affects the transmission as a function of temperature. The knowledge of the fundamental absorption processes is then used to predict the ultimate temperature ranges over which the technique will be useful.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Electrical and Electronic Engineering