Single spherical mirror optic for extreme ultraviolet lithography enabled by inverse lithography technology

Area of Science:

• Optics and Photonics
• Semiconductor Manufacturing
• Computational Lithography

Background:

• Extreme ultraviolet (EUV) lithography traditionally uses multiple mirrors for aberration correction, leading to high source power demands.
• Lossy mirrors in conventional EUV projection optics necessitate substantial power input, hindering efficiency.

Purpose of the Study:

• To investigate a single spherical mirror projection system for EUV lithography.
• To demonstrate aberration correction using Inverse Lithography Technology (ILT) integrated into the mask design.
• To reduce power requirements for EUV lithography by minimizing optical components.

Main Methods:

• Modeling a single spherical mirror system with significant inherent spherical aberration.
• Implementing Inverse Lithography Technology (ILT) via an adjoint-based gradient descent optimization algorithm.
• Designing photomasks to compensate for large optical aberrations.

Main Results:

• Successfully designed photomasks capable of printing test patterns despite substantial spherical aberrations.
• Demonstrated the feasibility of aberration correction through mask-based ILT in a simplified optical system.
• The ILT method was validated using a 6-plane wave illumination source.

Conclusions:

• A single mirror EUV projection system with ILT-based mask correction is a viable alternative to multi-mirror systems.
• ILT offers a pathway to reduce power consumption in EUV lithography.
• Further research is needed to optimize power throughput with incoherent sources.