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Elimination of Secondary and Tertiary Interferograms in Fourier Transform Spectroscopy of Semiconductor Wafers

Volume 36, Number 3 (June 1982) Page 319-319

Griffiths, Peter R.

In a recent paper in this journal, Baghdadi and Forman showed that multiple reflections, occurring both within a semiconductor specimen and between the specimen and the interferometer, give rise to a series of "secondary" and "tertiary" interferograms which are displaced from the main centerburst. Secondary interferograms arise from multiple internal reflections inside the wafer, whereas tertiary interferograms arise from radiation which reflects from the surface of the wafer back into the interferometer and is modulated a second time before it is measured at the detector. The effect of both interferograms is the generation of sinusoidal artifacts in the resulting spectrum which reduce the accuracy to which bands caused by the presence of impurities in the silicon can be measured. A number of different ways of removing the effects of secondary interferograms have been proposed and Baghdadi and Forman showed that the Hirschfeld-Mantz method could be used to reduce, but not entirely eliminate, the amplitude of the channel spectrum resulting from secondary and tertiary interferograms.