Improving feature size uniformity from interference lithography systems with non-uniform intensity profiles.

Area of Science:

• Nanofabrication
• Lithography
• Materials Science

Background:

• Gaussian-like laser beams in interference lithography (IL) create non-uniform dose and feature sizes.
• Existing methods focus on IL system configuration, not photoresist response.

Purpose of the Study:

• To investigate photoresist response to non-uniform laser doses.
• To reduce feature size variation in 240 nm line/space patterns fabricated by IL.

Main Methods:

• Utilized a Lloyd's mirror IL system with a HeCd laser (325 nm).
• Exposed samples with varying average doses while maintaining a fixed intra-sample dose profile.
• Employed a binary model of photoresist response and experimental verification.
• Demonstrated an etch process to widen narrow features and fabricated a silicon nanoimprint mold.

Main Results:

• Experimentally verified a reduction in line width range from 50 nm to 16 nm with a 60% dose increase.
• Observed a decrease in the narrowest line width from 120 nm to 65 nm.
• Successfully fabricated a silicon nanoimprint mold using the developed technique.

Conclusions:

• Photoresist response is a critical factor in managing non-uniformity in IL.
• Increasing the overall laser dose is an effective strategy to improve feature size uniformity.
• The demonstrated etch process and nanoimprint mold fabrication show the practical applicability of the findings.