Interference method of measuring distribution of refractin index continuous heterogeneities in semiconductors are described. Difference distributions of sample thickness and refracting index are calculated by scanning three interferograms and making use of computer analysis. Distributions of sample cuneiformity and refracting index gradient may also be found as well as the speed of variation of these quantities with respect to the variation of coordinates. Measuring results of silicon sample are given. Measuring accuracy 1x10-5 may be achieved for refracting index distribution in 1 mm-thick semiconductor sample.
"Interferometric Measurement Of Heterogeneities In Semiconductors", Proc. SPIE 0136, 1st European Conf on Optics Applied to Metrology, (18 April 1978); doi: 10.1117/12.956130; https://doi.org/10.1117/12.956130