Sub-1 nm misalignment sensing with cascaded interference in polar coordinate for lithography

Area of Science:

• Optical Metrology
• Nanotechnology
• Precision Engineering

Background:

• Previous structured illumination methods achieved sub-nanometer misalignment sensing using linear gratings.
• Limitations included the inability to use circular gratings due to pattern consistency requirements.

Purpose of the Study:

• To propose a novel misalignment sensing method using cascaded interference in polar coordinates.
• To enable the use of sub-wavelength circular gratings for sub-nanometer alignment.

Main Methods:

• Development of a cascaded interference technique in polar coordinates.
• Implementation with sub-wavelength circular gratings for misalignment sensing.

Main Results:

• Demonstration of 2D misalignment measurement.
• Achieved an accuracy of 0.62 nm across a 50 µm range.

Conclusions:

• The proposed method overcomes limitations of linear gratings.
• Offers a robust solution for wide-range, high-precision 2D alignment.