Accurate measurement and adjustment method for interference fringe direction in a scanning beam interference...

Area of Science:

• Optical Engineering
• Nanofabrication
• Metrology

Background:

• Scanning Beam Interference Lithography (SBIL) is crucial for high-precision grating fabrication.
• Exposure contrast in SBIL is sensitive to directional errors, impacting grating quality.
• Existing methods lack sufficient accuracy in measuring and correcting these directional errors.

Purpose of the Study:

• To establish a mathematical model for scanning exposure in SBIL, incorporating measurement mirror direction error.
• To analyze the impact of the angle between interference fringe direction and measurement mirror direction on exposure contrast.
• To propose and validate an accurate method for measuring and adjusting this critical angle.

Main Methods:

• Developed a mathematical model for scanning exposure, including measurement mirror direction error.
• Proposed an accurate interference fringe direction measurement method using heterodyne interferometry and metrology gratings.
• Combined diffraction characteristics of metrology gratings with phase shift interferometry for angle calculation and adjustment.

Main Results:

• Achieved an angle measurement accuracy of 0.6777 µrad, meeting high-precision grating fabrication demands.
• Demonstrated that a smaller angle significantly improves grating groove production quality.
• Validated theoretical analysis and the feasibility of the proposed interference fringe direction adjustment method.

Conclusions:

• The developed mathematical model accurately predicts the effect of directional errors on SBIL exposure contrast.
• The proposed measurement and adjustment method effectively controls the angle for enhanced grating fabrication.
• This work lays a foundation for achieving high-quality grating fabrication using SBIL systems.