8 October 2014 Impact of B4C capping layer for EUV mask on the sensitivity of patterned mask inspection using projection electron microscope
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Abstract
The inspection sensitivity of a patterned extreme ultraviolet (EUV) mask with B4C capped multilayer (ML) was investigated using a simulated projection electron microscope (PEM) image. Extrusion and intrusion defects with 16 nm in size were detected with their intensity of > 10 times the standard deviation of the background level on a half-pitch (hp) 64 nm line and space pattern. The defect detection sensitivity in this case was higher than that of Ru capped ML sample, and has a potential to meet the requirement for beyond 16 nm node generation from the standpoint of patterned mask inspection using the PEM technique. These results indicate that B4C capping layer besides its good durability has an advantage for high sensitivity of patterned mask inspection. The optimal condition of the incident beam energy was found to be 500 and 1000 eV for the samples of B4C capped ML and B4C buffered Ru capped ML, respectively. The sensitivity of defect detection was strongly affected by the difference of secondary electron emission coefficients (SEECs) between the absorber layer and capping layer. However, severely scattered electrons near the pattern edge become a source of noise and then they block the effect of large SEEC difference. Thus, the small incident beam energy was found to be preferable when the SEEC difference was relatively high.
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Susumu Iida, Ryoichi Hirano, Tsuyoshi Amano, Hidehiro Watanabe, "Impact of B4C capping layer for EUV mask on the sensitivity of patterned mask inspection using projection electron microscope", Proc. SPIE 9235, Photomask Technology 2014, 92351B (8 October 2014); doi: 10.1117/12.2065655; https://doi.org/10.1117/12.2065655
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