High-speed lateral scanning white-light phase shift interferometry

Area of Science:

• Metrology
• Optical Engineering
• Surface Metrology

Background:

• Traditional white light interferometry (WLI) faces limitations in inspecting large fields of view (FOV) at high speeds.
• Phase-shifting algorithms require specific interference signal acquisition conditions, often limiting measurement speed.
• Achieving high-resolution topography over extended areas necessitates advancements in interferometric techniques.

Purpose of the Study:

• To introduce and validate a novel lateral scanning white light interferometry (LS-WLI) technique.
• To enhance the speed and efficiency of topographic measurements for large FOV applications.
• To adapt phase-shifting algorithms for high-speed, large-area surface inspection.

Main Methods:

• Development of a lateral scanning white light interferometry (LS-WLI) system.
• Application of phase-shifting algorithms adapted for stretched fringe spacing.
• Acquisition of interference signals under specific conditions to meet phase-shifting requirements.
• High-speed data acquisition and processing for topographic mapping.

Main Results:

• Successful implementation of LS-WLI for large FOV topographic inspection.
• Demonstration of high-speed measurements with enhanced stage speed at a fixed camera speed.
• Generation of a laterally expanded topographic image measuring 5.25 mm × 1.25 mm.
• Accurate measurement of microstructure step height as 140 nm.

Conclusions:

• LS-WLI effectively overcomes the limitations of traditional WLI for large-area, high-speed topographic measurements.
• The adapted phase-shifting technique enables faster stage movement without compromising measurement accuracy.
• This method provides a robust solution for detailed microstructure analysis over extended fields of view.