Generalized inverse lithography methods for phase-shifting mask design.

Area of Science:

• Semiconductor Manufacturing
• Computational Lithography
• Optical Engineering

Background:

• Optical proximity correction (OPC) and phase shifting masks (PSM) are crucial resolution enhancement techniques (RET) in semiconductor manufacturing.
• Existing methods often face limitations in pattern fidelity and manufacturability for advanced lithography.

Purpose of the Study:

• To develop generalized gradient-based optimization methods for the inverse lithography problem.
• To design efficient phase shifting masks (PSMs) with arbitrary discrete phases.
• To enhance manufacturability of lithographic patterns using novel regularization techniques.

Main Methods:

• Generalized gradient-based RET optimization allowing arbitrary complex search spaces.
• Mask quantization for designing PSMs with multiple discrete phases.
• Wavelet regularization framework for improved pattern manufacturability.
• Double-exposure optimization for general inverse lithography.

Main Results:

• Development of highly effective four-phase PSMs for arbitrary Manhattan geometries.
• Demonstration of arbitrary search trajectories in complex space for RET.
• Introduction of a wavelet regularization framework offering localized flexibility.
• Successful design of double-exposure optimization using two-phase masks.

Conclusions:

• The proposed methods enable efficient design of advanced PSMs for semiconductor lithography.
• Wavelet regularization enhances pattern manufacturability beyond traditional methods.
• The double-exposure technique offers a new approach for inverse lithography optimization.