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Large-field step-structure surface measurement using a femtosecond laser
Optics Express
|August 6, 2020
Summary
A femtosecond laser interferometry system enables precise step-structure surface measurement over a large field of view. This advanced technique achieves nanometer-level precision for micro/nano-device manufacturing.
Area of Science:
- Optics and Photonics
- Metrology
- Surface Science
Background:
- Accurate surface measurement is critical for micro/nano-device fabrication.
- Existing interferometry methods face limitations in field of view or precision.
Purpose of the Study:
- To develop a femtosecond laser-based interferometry system for large-field, high-precision surface measurement.
- To demonstrate the system's capability for step-structure metrology.
Main Methods:
- Utilized femtosecond laser interferometry with repetition frequency scanning for a 348 µm axial scanning range.
- Employed a combined method: envelope peak positioning, synthetic-wavelength interferometry, and carrier wave interferometry.
- Achieved a 17.3 mm field of view, expandable due to the laser's spatial coherence.
Main Results:
- Successfully measured a three-step specimen with 7 nm height precision.
- Verified accuracy against a commercial white light interferometer.
- Demonstrated potential for large-field, high-precision measurements.
Conclusions:
- The femtosecond laser system integrates the benefits of white light and phase shifting interferometry.
- This technology shows significant potential for ultra-precision manufacturing of micro/nano-devices.
- Applications include semiconductor chips, integrated circuits, and micro-electro-mechanical systems.
