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13 October 2011 Electron beam EUV patterned mask inspection system
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EUV lithography is expected to begin production in 2014. Production of successful EUV photomasks requires patterned mask inspection (PMI). The ultimate PMI tool is expected to utilize actinic (EUV) illumination. Development of such a tool is expected to require three years after funding. Current test EUV masks, such as 22 nm, can be inspected using 193 nm wavelength deep UV (DUV) inspection tools similar to those currently being used for DUV masks. The DUV inspection tools may be extended for the 16 nm node. However EUV production is expected to start with 11 nm node masks which cannot be inspected with proposed DUV inspection tools. Therefore E-beam inspection (EBI) is discussed as the interim PMI method. EBI has the advantage of high resolution and the disadvantages of low inspection speed and relative insensitivity to ML defects (in the multi-layer material). EBI inspection speed is limited by the pixel size, pixel capture rate and the number of electron columns. The pixel rate is limited by the detector time-resolution, the beam current, and the detection efficiency. Technical improvements in beam focus, secondary electron detection, and defect detection and analysis provide good performance for 22 nm node masks. We discuss the advances and show that performance can be extrapolated for 16 and 11 nm node patterned mask inspections. We present sensitivity and false-defect frequency results of using the Holon EBI tool on 22 nm test masks and a roadmap for extending its operation for use on 16 and 11 nm node masks for inspections requiring 2-5 hours per mask.
© (2011) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Keizo Yamada, Yasunobu Kitayama, and Peter Fiekowsky "Electron beam EUV patterned mask inspection system", Proc. SPIE 8166, Photomask Technology 2011, 81662W (13 October 2011);

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