Scatterfield microscopy for extending the limits of image-based optical metrology

Area of Science:

• Optical Metrology
• Microscopy Techniques
• Nanoscale Imaging

Background:

• Existing optical metrology methods face limitations with sub-50-nm features and dense pitches.
• Previous scatterfield microscopy demonstrated success with sparse features beyond the Rayleigh resolution criterion.
• The need for advanced techniques to measure increasingly dense nanoscale features is critical.

Purpose of the Study:

• To extend scatterfield microscopy techniques for measuring dense nanoscale features.
• To develop and analyze a novel approach combining zero-order optical response and edge-based imaging.
• To determine the ultimate limits of feature size and density measurable with these optical techniques.

Main Methods:

• Engineered illumination combined with specialized metrology targets.
• Development of a new approach using zero-order optical response and edge-based imaging.
• Comprehensive theoretical analysis and evaluation using electromagnetic scattering simulations.
• Experimental validation of the developed techniques.

Main Results:

• Demonstrated capability to image and measure features much denser than the conventional Rayleigh resolution criterion.
• Theoretical analysis provides a direct measure of the ultimate size and density limits.
• Experimental results and simulations confirm the sensitivity and extensibility of the scatterfield microscopy approach.

Conclusions:

• Scatterfield microscopy, particularly with the new zero-order and edge-based imaging approach, significantly extends optical metrology capabilities.
• The techniques enable precise measurement of dense nanoscale features previously unachievable.
• This work provides a framework for understanding and pushing the boundaries of optical measurement sensitivity and resolution.