Condenser optics, partial coherence, and imaging for soft-x-ray projection lithography.

Area of Science:

• Optics and Photonics
• Lithography Technology
• Plasma Physics

Background:

• Condenser systems are crucial for controlling illumination uniformity and partial coherence in imaging systems.
• Soft-x-ray projection lithography presents unique design challenges for condenser systems due to its specific source and imaging requirements.
• Achieving precise control over illumination is vital for high-resolution aerial imaging.

Purpose of the Study:

• To propose and evaluate novel condenser system designs for soft-x-ray projection lithography.
• To address the constraints imposed by ring-field imaging and laser-produced plasma x-ray sources.
• To ensure optimal uniformity and partial coherence at the object plane for improved lithography performance.

Main Methods:

• Two condenser designs, critical illumination and Köhler illumination, were developed.
• Each design utilizes a three-mirror configuration.
• Scanning mechanisms were incorporated to cover the entire ring field with desired illumination properties.
• Image simulations were performed using Hopkins' formulation for partially coherent imaging.

Main Results:

• Both proposed condenser designs enable control over uniformity and partial coherence.
• The three-mirror system with scanning effectively covers the ring field.
• Simulations demonstrate the impact of condenser design on aerial image characteristics.

Conclusions:

• The proposed condenser designs are suitable for soft-x-ray projection lithography.
• Effective control of illumination parameters is achievable with the presented optical configurations.
• The study provides a foundation for optimizing condenser systems in advanced lithography applications.