Design of angle-resolved illumination optics using nonimaging bi-telecentricity for 193 nm scatterfield microscopy

Area of Science:

• Optical Metrology
• Microscopy
• Nanotechnology

Background:

• Accurate dimensional measurements of sub-diffraction limit features require detailed knowledge of optical illumination and scattered light fields.
• Scatterfield microscopy combined with simulations and angle-resolved tool characterization can achieve sub-nanometer uncertainties.
• Existing methods face challenges in precisely controlling illumination angles for quantitative metrology.

Purpose of the Study:

• To design and validate bi-telecentric illumination optics for angle-resolved scatterfield microscopy.
• To enable precise control over illumination beam angles with minimal distortion for improved metrology.
• To enhance the measurement accuracy of deep-subwavelength structures using deep-ultraviolet light.

Main Methods:

• Implementation of a bi-telecentric optical system with Köhler illumination.
• Utilizing a telecentric conjugate back focal plane (CBFP) for aperture or source scanning.
• Characterization of angle-resolved illumination beams for distortion and wavefront deviations.

Main Results:

• A novel bi-telecentric illumination optics design was successfully developed.
• The design enables angle-resolved illumination in both aperture and source scanning modes.
• Optimized design achieved a maximum chief ray angle of 0.002° at the CBFP and wavefront deviations < 0.06 λ.

Conclusions:

• The developed bi-telecentric optics provide high-quality angle-resolved illumination.
• This advancement promises improved quantitative metrology for deep-subwavelength structures.
• The system offers low distortion and chief ray parallelism crucial for accurate measurements.