Subwavelength resist patterning using interference exposure with a deep ultraviolet grating mask: Bragg angle...

Area of Science:

• Nanofabrication
• Optical Lithography
• Materials Science

Background:

• Deep-ultraviolet (DUV) interference lithography enables subwavelength pattern creation for visible wavelengths.
• High aspect ratio patterns, fringe visibility, and exposure uniformity are critical for sub-200 nm period fabrication.

Purpose of the Study:

• Investigate grating mask strategies for DUV interference lithography.
• Optimize mask setup and illumination for high-quality subwavelength pattern manufacturing.
• Determine optimal grating orientation (air vs. liquid interface) for index matching.

Main Methods:

• Utilized a two-beam interference lithography setup with liquid immersion.
• Employed a fused-silica grating mask operated under Bragg geometry.
• Analyzed the impact of grating orientation and liquid immersion on pattern quality.

Main Results:

• Liquid immersion and a two-beam configuration are necessary but insufficient for high aspect ratio patterns.
• Bragg geometry with a fused-silica grating and high-index liquid immersion is the most feasible method for sub-200 nm periods.
• Grating orientation relative to the liquid interface is crucial for maintaining beam-splitting properties.

Conclusions:

• A specific grating mask strategy involving Bragg geometry and liquid immersion is essential for DUV interference lithography.
• Optimizing the grating-resist interface with high-index liquid is critical for achieving sub-200 nm resolution.
• This approach provides a viable pathway for fabricating advanced optical components.