Multi-Repeated Projection Lithography for High-Precision Linear Scale Based on Average Homogenization Effect.

Area of Science:

• Manufacturing Technology
• Metrology
• Optical Engineering

Background:

• Incremental linear scales are crucial for precision measurement systems.
• Traditional projection lithography faces limitations in achieving high accuracy for linear scales.
• Mask errors and alignment issues in lithography impact the uniformity and precision of manufactured scales.

Purpose of the Study:

• To present a multi-repeated photolithography method for manufacturing high-accuracy incremental linear scales.
• To improve the pitch accuracy and overall length precision of linear scales.
• To analyze and mitigate intensity errors in the focal plane during lithography.

Main Methods:

• Utilizing a multi-repeated photolithography approach with projection lithography.
• Applying an average homogenization effect by superposing light intensity from different mask pitch locations.
• Adjusting repeat exposure numbers and exposure spacing for optimized black and white stripe proportions.

Main Results:

• Theoretical error within 0.01 µm for a 2-µm sine-wave error mask.
• Reduced impact of mask errors, static positioning, and focal plane alignment errors on pitch uniformity compared to common methods.
• Achieved pitch accuracy of 43 nm at 10 locations over 1 m.
• Demonstrated whole length accuracy of less than 1 µm/m.

Conclusions:

• The multi-repeated photolithography method effectively enhances the accuracy of incremental linear scales.
• This technique offers a viable solution for achieving sub-micrometer length accuracy in precision manufacturing.
• The findings confirm the potential for improved precision in metrology and automation systems.