High-numerical-aperture effects in photoresist

Area of Science:

• Optics and Photonics
• Materials Science
• Lithography

Background:

• Understanding polarized light behavior is crucial for advanced lithography.
• Thin photoresist films are key components in microfabrication processes.
• High-numerical-aperture (NA) illumination significantly influences lithographic outcomes.

Purpose of the Study:

• To investigate and highlight the distinct effects of s-polarized and p-polarized light in vector interference lithography.
• To compare simulation and experimental results for various photoresist and substrate configurations.
• To analyze the impact of illumination polarization on feature formation and image quality.

Main Methods:

• Utilizing two-beam and three-beam vector interference techniques.
• Performing both optical simulations and experimental validations.
• Examining undyed and dyed photoresist on silicon substrates, with and without anti-reflective layers.
• Employing a high-numerical-aperture (NA) system (0.85 NA).

Main Results:

• Observed striking differences in interference patterns between s-polarized and p-polarized illumination.
• Documented variations in feature shapes, with p-polarized light yielding more elliptical features compared to rectangular features from s-polarized light.
• Reported lower image contrast for p-polarized illumination.
• Confirmed simulation results through experimental data across different sample configurations.

Conclusions:

• Polarization state critically affects high-NA lithography outcomes in photoresist films.
• s-Polarization generally leads to sharper, more rectangular features, while p-polarization results in broader, elliptical features and reduced contrast.
• The findings provide essential insights for optimizing lithographic processes by controlling illumination polarization.