Method and apparatus measure the thickness of an epi layer grown on a substrate. IR energy 12 is directed onto the epi layer 13 and a portion 14 of the energy is reflected from the surface of the epi layer and from the interface of the epi layer and substrate. The spectral reflectance of the reflected...http://www.google.de/patents/US4555767?utm_source=gb-gplus-sharePatent US4555767 - Method and apparatus for measuring thickness of epitaxial layer by infrared reflectance
