page_title: Extreme ultraviolet lithography
section_title: Reduced fields
hierarchical_section_title: Extreme ultraviolet lithography / Throughput-scaling limits / Reduced fields
caption_attribution_description: English: Features patterned across adjacent features are subject to stitching faults. Ref.:S-Y. Fang et al., DAC 2013 [1]
context_page_description: Extreme ultraviolet lithography is a lithography technology using a range of extreme ultraviolet wavelengths, roughly spanning a 2% FWHM bandwidth about 13.5 nm.
  While EUV technology is available for mass production, 53 machines worldwide capable of producing wafers using the technique were delivered since Q1 2018, while 201 immersion lithography systems were delivered during the same period. Issues that make EUV adoption difficult are tool costs, tool uptime and stochastic phenomena. The latest NXE:3400 tools have been equipped with lower pupil fill capability for better imaging, but this leads to lower productivity due to limited use of the exposure field.
context_section_description: Preparation of an anamorphic lens with an NA between 0.5 and 0.6 is underway as of 2016. The demagnification will be 8X in one dimension and 4X in the other, and the angle of reflection will increase.
  Higher demagnification will increase the mask size or reduce the size of the printed field. Reduced field size would divide full-size chip patterns (normally taking up 26 mm × 33 mm) among two or more conventional 6-inch EUV masks. Large (approaching or exceeding 500 mm²) chips, typically used for GPUs or servers, would have to be stitched together from two or more sub-patterns from different masks. Without field stitching, die size would be limited. With field stitching, features that cross field boundaries would have alignment errors, and the extra time required to change masks would reduce the throughput of the EUV system.
caption: Field stitching. Stitching together exposure fields is a concern where critical features cross a field boundary (red dotted line).
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