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289 (1996) [2]). Purpose of this paper is to present an extension of this method to characterisation of ultra-thin compound wide bandgap wafers mounted on insulating carriers. We present alternative technique, which does not suffer from above discussed limitations, and can be easily integrated in the production tools, and provide accurate measurement of samples while they are being processed. IntroductionThe metrology of thin (0.1-0.2 mm) and ultra-thin (below 0.1 mm) semiconductor compound materials wafers has been identified very early as one of the technology gaps of the industry. The most commonly employed metrologies include capacitance and air pressure techniques. These two competing technologies have been proven to be reliable and quite accurate solutions for measurement of thickness, bow, warp and related parameters in relatively thick and well conducting materials.

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Single probe infrared low coherence optical interferometry has been proven to be an effective tool for characterization of thin and ultra-thin semiconductor Si and compound materials wafers. Its application was however limited to wafers transparent at probing wavelength, and having relatively smooth surfaces. Purpose of this paper is to present an extension of low coherence interferometry to characterization of non-transparent wafers, and wafers with rough surfaces.