When temperatures are measured on silicon coated with Si3N4or SiO2layers using an infrared radiation pyrometer, large differences in temperature have been observed on slices with the same true temperature. Analysis of this phenomenon reveals that the emission coefficient of the combined siliconhyphen;layer system is determined by the thickness of the Si3N4or SiO2layer and the angle of observation. From calculations it follows that the value of the emission coefficient of coated Si may vary from 0.66 to 1.0. The variation of the emissivity as a function of the thickness of the dielectric layer is represented in a graph, by means of which the observed temperature readings can be converted into true temperatures. Good correlation with experiment is obtained. On the other hand, when the emissivity is calculated for the epitaxial system Si/Si3N4/Si or Si/SiO2/Si the maximum value of the emission coefficient is 0.5, independent of the dielectric coating (Si3N4or SiO2).
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