6 December 2004 Evaluation of multilayer damage in EUVL mask fabrication process
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To obtain a high throughput and good CD uniformity, the EUV reflectivity of EUVL masks must be high and very uniform. In this study, EUVL masks were fabricated, and the degradation in EUV reflectivity due to the fabrication process was evaluated. The damage to the multiplayer due to plasma etching appeared as a drop in peak reflectivity of about 2.0%. Etching the Cr buffer layer by a wet process reduced the value to within the measurement error. On the other hand, thermal damage appeared as both a drop in peak reflectivity and a shift in centroid wavelength. The drop in peak reflectivity was about 0.5-1.0% in the temperature range 140-240° C, and about 1.5% in the temperature range 260-280°C. The shift in centroid wavelength increased monotonically as the temperature rose from 180degrees C to 280°C. To ensure good CD uniformity, both the shift and the variation in centroid wavelength should be kept within ∓0.02 nm. If a drop in peak reflectivity of 1-2% is acceptable, annealing could be an effective way to adjust the centroid wavelength by as much as 0.10 nm with an accuracy of ∓0.01 nm.
© (2004) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Yuusuke Tanaka, Iwao Nishiyama, Tsukasa Abe, Shiho Sasaki, Naoya Hayashi, "Evaluation of multilayer damage in EUVL mask fabrication process", Proc. SPIE 5567, 24th Annual BACUS Symposium on Photomask Technology, (6 December 2004); doi: 10.1117/12.568984; https://doi.org/10.1117/12.568984

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