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In situ measurement of etch rate of single crystal silicon

This paper reports on a simple method for in situ monitoring of silicon etch rate in watery solutions by laser reflectance interferometry. Accurate measurements of etch rate can be obtained by long term etching on one sample. All changes in etch rate due to the etchant or the sample itself can be observed in real time. The method is demonstrated by etching lightly- and heavily doped silicon at various temperatures. The first results also indicate a correlation between the optical signal intensity and the surface roughness of the sample under etching. Preliminary experimental results with in situ thickness monitoring using a spectroscopic reflectance interference technique are also given.