Scanning electron microscope line-profile analysis of less-than-10-nm patterns

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Scanning electron microscopes (SEMs) are widely used in various fields and have contributed to advances in nanotechnology. To analyse SEM images, it is necessary to consider the size of the probe electron (PE) beam and the range of PE scattering inside the pattern because they affect edge sharpness in SEM images. As the feature size of the sample drops to less than 10 nm, their effects become even more noticeable. In this study, we utilized Monte-Carlo simulation to clarify the effects of the size of the PE beam and the range of PE scattering for patterns with a line width less than 10 nm. Using a reference pattern with a known cross-sectional shape, we determined the PE beam full-width at half maximum (FWHM) for the simulation by fitting the simulation line profile to the experimental one. The resultant simulation SEM images matched the experimental ones for various PE beam FWHM conditions at acceleration voltages of 500 to 2400 V, even though the pattern dimensions differed from those of the reference pattern. These results indicate that analysis using Monte-Carlo simulation is an effective approach to clarifying SEM image formation and that the optimum observation conditions for patterns with a line width even less than 10 nm can be explored using simulation.