Spectrally resolved phase-shifting interference microscopy: technique based on optical coherence tomography for...

Area of Science:

• Optical microscopy
• Thin-film metrology
• Spectroscopy

Background:

• Measuring thin-film thickness on patterned structures is challenging.
• Existing methods may struggle with steps and discontinuities.
• Accurate metrology is crucial for microelectronics and optics.

Purpose of the Study:

• To develop a direct method for measuring the thickness profile of transparent thin films.
• To address challenges posed by patterned substrates with steps.
• To utilize spectrally resolved white-light interference microscopy and optical coherence tomography principles.

Main Methods:

• Employs spectrally resolved white-light phase-shifting interference microscopy.
• Adapts principles from spectrally resolved optical coherence tomography.
• Utilizes inverse Fourier transformation of the complex spectral interference function.

Main Results:

• Successfully obtained a direct thickness profile of a transparent thin film.
• Demonstrated capability on a patterned structure with steps and discontinuities.
• The technique provides line profile measurements.

Conclusions:

• A simple and effective technique for thin-film thickness profiling is presented.
• The method is suitable for transparent films on complex substrates.
• Inverse Fourier transformation of spectral interference data is key to direct profiling.