20 April 2011 A method for improving resolution of a scanning electron microscope for inspection of nanodevices
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Abstract
A method for improving the resolution of a scanning electron microscope (SEM) designed for inspection of nanodevices was developed. The trade-off between the resolution and depth of focus of the SEM was quantitatively evaluated by a method based on "information passing capacity". It was theoretically and experimentally shown that depth of focus is enhanced under observation conditions with increased pixel size. Furthermore, increasing depth of focus is effective in obtaining high-resolution images because increasing the pixel size of the formed SEM image maintained the focal plane of the electron beam. The maximum axial magnetic field and the focal length of the objective lens in the SEM optics needed to obtain a resolution of 0.9 nm were determined theoretically. The maximum axial magnetic field can be strengthened by improving the immersion lens in the SEM optics in terms of geometry and material composition. The focal length was reduced by adopting the immersion lens and by dynamically controlling the electron beam by deflectors as well as optical correctors. This method will be applied in developing apparatuses for R&D purposes as well as for improving the yield of the production process for integrated circuits.
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Muneyuki Fukuda, Noritsugu Takahashi, Tomoyasu Shojo, Hiroya Ohta, Hiroshi Suzuki, "A method for improving resolution of a scanning electron microscope for inspection of nanodevices", Proc. SPIE 7971, Metrology, Inspection, and Process Control for Microlithography XXV, 797110 (20 April 2011); doi: 10.1117/12.879042; https://doi.org/10.1117/12.879042
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