3D modeling of coherence scanning interferometry on 2D surfaces using FEM

Area of Science:

• Optical metrology
• Surface topography measurement
• Interferometry

Background:

• Optical profilers, including coherence scanning interferometers, are widely used for contactless topography measurements.
• Measured profiles often exhibit systematic deviations due to the wave nature of light, which are not fully understood.
• Existing models may not fully capture the complexities of image formation for 2D surface structures in 3D.

Purpose of the Study:

• To rigorously analyze systematic deviations in optical profiler measurements.
• To investigate the physical relationships between measurement deviations and surface characteristics.
• To compare the efficacy of 3D modeling versus 2D approaches for topography analysis.

Main Methods:

• Development and application of a rigorous 3D simulation model for optical profiler image formation.
• Consideration of instrument transfer characteristics, object geometry, and material properties.
• Comparison of simulation results with experimental measurements using varying polarizations, wavelengths, and interferometer types. Finite Element Method (FEM) simulations were employed using AFM data for realistic results.

Main Results:

• The study provides a full 3D modeling approach for image formation concerning 2D surface structures.
• Simulation results are validated against experimental data for various surface features (edges, slopes) and materials.
• The research highlights the advantages of 3D modeling over time-efficient 2D methods for analyzing measurement deviations.

Conclusions:

• Rigorous 3D simulation is crucial for accurately understanding and mitigating systematic deviations in optical topography measurements.
• The developed model accurately predicts deviations caused by surface geometry and material properties.
• This work advances the accuracy and reliability of contactless surface topography analysis using optical methods.