Abstract

We describe a new interferometric technique using polarisation measurements which eliminates the need to count fringes, giving an unambiguous measurement of surface height. Applicable to the whole image, the height of each pixel element is determined independently without the need for scanning optical components. The technique is based on analysis of the polarisation state of the light reflected from the surface following its interference with an orthogonally polarised reference beam. We have demonstrated its viability by imaging the surface of a processed silicon wafer, identifying the heights of various layers even though separated by many optical wavelengths.

© 1998 IEEE