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EUV lithography is the most promising technology for semiconductor device manufacturing of the 10nm node and
beyond. The image border is a pattern free dark area around the die on the photomask serving as transition area between
the parts of the mask that is shielded from the exposure light by the Reticle Masking (REMA) blades and the die. When
printing a die at dense spacing on an EUV scanner, the reflection from the image border overlaps edges of neighboring
dies, affecting CD and contrast in this area. This is related to the fact that EUV absorber stack reflects 1-3% of actinic
EUV light. To reduce this effect several types of image border with reduced EUV reflectance (<0.05%) have been
proposed; such an image border is referred to as a black border. In particular, an etched multilayer type black border was
developed; it was demonstrated that CD impact at the edge of a die is strongly reduced with this type of the black border
(BB). However, wafer printing result still showed some CD change in the die influenced by the black border reflection. It
was proven that the CD shift was caused by DUV Out of Band (OOB) light from the EUV light source. New types of a
multilayer etched BB were evaluated and showed a good potential for DUV light suppression.
In this study, a novel BB called ‘Hybrid Black Border’ (HBB) has been developed to eliminate EUV and DUV OOB
light reflection by applying optical design technique and special micro-fabrication technique. A new test mask with HBB
is fabricated without any degradation of mask quality according to the result of CD performance in the main pattern,
defectivity and cleaning durability. The imaging performance for N10 imaging structures is demonstrated on
NXE:3300B in collaboration with ASML. This result is compared to the imaging results obtained for a mask with the
earlier developed BB, and HBB has achieved ~3x improvement; less than 0.2 nm CD changes are observed in the
corners of the die. A CD uniformity budget including impact of OOB light in the die edge area is evaluated which shows
that the OOB impact from HBB becomes comparable with other CDU contributors in this area. Finally, we state that
HBB is a promising technology allowing for CD control at die edges.
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