A new evaluation method for interferometric surface topography measurements which is robust against environmental disturbances

Abstract Installing manufacturing metrology as close as possible to the production line is the key to short feedback times to process parameters. Apart from finding the appropriate measurement technique with the required resolution, the solution has to be applied under unavoidable production conditions. Although white light interferometers (WLI), which provide surface data with details in micro- and nanometer dimensions, are accepted as important tools of modern manufacturing metrology, it should be borne in mind that environmental factors like vibrations may be a significant contributor to the measurement uncertainty without appropriate precautions. Measured surface topography raw data can be affected by disturbances of the optical path length of the interferometer caused by e.g. vibrational excitation, which is typical in the production environment, or by local variations of the refractive index of the medium caused by turbulence due to strong temperature variations. A new method which significantly reduces the effects of these environmental interferences is described in this paper. Unlike other techniques, which tend to create artefacts that are larger in amplitude than the disturbances, the new method is more robust and does not require explicit identification and compensation of external noise. Following a description of the implementation of this robust method, some case studies from real world applications are shown.