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Discrepancies between roughness measurements obtained with phase-shifting and white-light interferometry
Hyug-Gyo Rhee1, Theodore V Vorburger, Jonathan W Lee
1Precision Engineering Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8212, USA. hrhee@nist.gov
Applied Optics
|October 20, 2005
Summary
Discrepancies in step-height and surface roughness measurements between phase-shifting and white-light interferometry are linked to surface roughness. The skewing effect in white-light interferometry is a key factor causing these measurement issues.
Area of Science:
- Metrology and Surface Characterization
- Optical Measurement Techniques
Background:
- Phase-shifting interferometry (PSI) and white-light interferometry (WLI) are common techniques for surface metrology.
- Observed discrepancies exist between PSI and WLI measurements for step-height and surface roughness.
Purpose of the Study:
- To investigate the causes of discrepancies between PSI and WLI measurements.
- To understand the relationship between these discrepancies and surface roughness parameters.
Main Methods:
- Analysis of measurement data from both phase-shifting and white-light interferometry.
- Correlation of observed discrepancies with the roughness average parameter.
- Identification of the skewing effect as a contributing factor in WLI for step-height measurements.
Main Results:
- Discrepancies between PSI and WLI are strongly related to the surface roughness average.
- The skewing effect, particularly near sample peaks, valleys, and edges, is identified as a cause for step-height discrepancies in WLI.
- Two potential sources for discrepancies in surface roughness measurements are proposed.
Conclusions:
- Surface roughness significantly influences the accuracy of interferometric measurements.
- The skewing effect in WLI needs consideration for accurate step-height profiling.
- Further investigation is required to fully understand roughness measurement discrepancies.