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The use of in situ diagnostic tools, allowing real-time control during plasma-processing steps, may become a key issue in designing robust processes and reducing costs for the next generations of integrated circuits. Real-time ellipsometry is capable of monitoring the growth and the etching of various materials, but its use has generally been restricted to unpatterned areas. In this study, we focus on the monitoring of polysilicon and poly SiGe gate patterning using real-time ellipsometry in the ultraviolet. It is shown that the same characteristic signature is obtained at the end of the polysilicon etching in unpatterned and low pattern-density areas. The analysis of this signature reveals the presence of a perturbed layer at the surface of polysilicon during etching. In addition, whatever the nature of the etched materials, the mask layout, and the underlying topography, ellipsometric real-time traces can be used for process end pointing and control. © 1997 American Vacuum Society.