Abstract: Phase stepping digital interference microscopy (PSM) is a measuring technique that can be used for the three-dimensional analysis of small surface defects in many microelectronic applications on bulk materials and epitaxial layers. If the resulting intensities for the interference after regular phase stepping are I$-1$/, I$-2$/,...,I$-p$/, where p $EQ 3,4,5,... according to the method, then the relief h(x,y) is given as a well known function of the I$-i$/. We have used fuzzy logic to improve the algorithms in order to secure the final result and also to afford a possibility for a subsample resolution: first we define into the I-space N fuzzy classes in a non linear way; then the regularity needed in phase stepping leads us to define theoretical p-uples of fuzzy classes. Finally we correct the p-uples of measured values (I$-1$/, I$-2$/,..., I$-p$/) according to the membershipness to the theoretical p-uples of fuzzy classes. These algorithms lead to important image improvements, offering better accuracy and a partial solution to the problem of image noise. !2
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