Optimal 3D phase-shifting masks in partially coherent illumination

Area of Science:

• Computational lithography
• Semiconductor manufacturing

Background:

• Thin-mask assumption limits phase-shifting mask (PSM) optimization in subwavelength lithography.
• Thick-mask effects, especially in etching profiles, degrade printing accuracy.
• Existing methods fail to account for these prevalent 3D effects.

Purpose of the Study:

• Develop novel three-dimensional phase-shifting mask (PSM) optimization methods.
• Overcome limitations of thin-mask assumptions in computational lithography.
• Address prevalent thick-mask effects in subwavelength lithography systems.

Main Methods:

• Developed gradient-based PSM optimization incorporating 3D effects.
• Utilized the boundary layer model to characterize and simplify thick-mask effects.
• Applied methods to lithography systems with partially coherent illumination.

Main Results:

• Demonstrated improved performance of 3D PSM optimization over thin-mask methods.
• Successfully accounted for aggravated thick-mask effects in simulations.
• Validated the effectiveness of the boundary layer model approach.

Conclusions:

• The developed 3D PSM optimization effectively mitigates thick-mask effects.
• This approach enhances computational lithography for subwavelength printing.
• Future work can further refine 3D modeling for advanced lithography.