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Interferometric analysis of nanostructured surface profiles: correcting material-dependent phase shifts
Leonid P Yatsenko1, Matthias Loeffler, Bruce W Shore
1Technical University of Kaiserlautern, 678653 Kaiserlautern, Germany.
Applied Optics
|June 9, 2004
Summary
This study introduces a new method to correct interferometry phase shifts caused by material variations on surfaces. This technique ensures nanometer accuracy for non-homogeneous materials, crucial for precise surface measurements.
Area of Science:
- Optical metrology
- Surface science
- Materials science
Background:
- Interferometry requires precise phase measurements for nanometer-accuracy surface characterization.
- Non-homogeneous surfaces introduce material-dependent phase shifts, complicating accurate measurements.
- Existing methods struggle with surfaces composed of multiple, unresolved materials.
Purpose of the Study:
- To develop a technique for correcting material-dependent phase shifts in interferometry.
- To enable nanometer-accuracy surface measurements on non-homogeneous materials.
- To adapt existing reflection theory for practical, two-material surface applications.
Main Methods:
- Adapted general reflection theory for surfaces with unresolved areas of multiple materials.
- Developed a method using three measured quantities and known optical constants.
- Validated the approach using numerical simulations for a two-material system (alumina with titanium carbide).
Main Results:
- The technique accurately determines material-dependent phase shifts on surfaces.
- Demonstrated nanometer accuracy even with a small numerical aperture in simulations.
- The method is effective for surfaces with embedded, optically unresolved granules.
Conclusions:
- The presented technique provides a reliable method for correcting phase shifts in interferometry.
- Achieves nanometer accuracy for non-homogeneous surfaces, enhancing metrology capabilities.
- Applicable to various interferometers and surface characterization challenges.