C3c measurement and dispersion reduction for beam-tilt optics of aberration-corrected SEM

To observe 3D structures of semiconductor devices, two beam-tilt observation methods for SEM were developed. The first is an aberration corrector with a tilted beam and the other is an aberration-measurement method for beam-tilt optics. The measured aberration coefficients show that the resolution of the tilted beam is restricted mainly by the dispersion of chromatic-spherical combination aberration. To reduce the dispersion of the tilted beam, a dispersion-suppression method was developed. Dispersion suppression improved the resolution of an SEM image to 2.7 nm at beam-tilt angle of 10° and landing energy of 800 eV.