Field-position dependent apodization in dark-field digital holographic microscopy for semiconductor metrology

Area of Science:

• Optics and Photonics
• Materials Science and Engineering
• Semiconductor Manufacturing

Background:

• Overlay metrology is critical for semiconductor fabrication.
• Existing methods face challenges in precision and accuracy.
• Accurate overlay measurement ensures device performance and yield.

Purpose of the Study:

• To introduce dark-field digital holographic microscopy for advanced overlay metrology.
• To investigate and explain the field-of-view dependency of the point-spread function.
• To propose mitigation strategies for observed optical effects.

Main Methods:

• Implementation of dark-field digital holographic microscopy.
• Analysis of point-spread function variations across the field-of-view.
• Theoretical modeling incorporating light source bandwidth and lens properties.

Main Results:

• Observed position-dependent point-spread function in the microscope.
• Attributed the effect to finite light source bandwidth and wavelength-dependent focal length.
• Validated theoretical model with experimental data.

Conclusions:

• The developed microscopy technique addresses key overlay metrology challenges.
• Understanding the optical aberrations is crucial for accurate measurements.
• Proposed solutions can reduce optical effects to acceptable levels for semiconductor manufacturing.