Patent ID: 7420164

Claim:
A method for evaluating a pattern on a sample plane with plural beams, comprising the steps of: (a) forming multiple beams by irradiating plural apertures with an electron beam emitted from an electron gun having a cathode; (b) forming a cross-over of a beam passed through the plural apertures on an aperture having a dimension substantially larger than a dimension of the cross-over or at a position in the vicinity of the aperture; (c) focusing a magnified cross-over by a condenser lens at a Z-coordinate position in the vicinity of a principal plane of an objective lens; (d) forming a reduced image of an image of the multiple beam on the sample plane with at least a reducing lens and an objective lens; (e) scanning the sample with the multiple-beams by using at least a two-stage deflector disposed between the reducing lens and the objective lens; (f) accelerating and focussing a secondary electron group emitted from the scanning point on the sample with an objective lens; (g) deflecting the secondary electron group passed through the objective lens with an electromagnetic deflector and sending it to a secondary optical system; (h) magnifying a mutual distance of the secondary electron group by the secondary optical system and leading the secondary electron group to plural secondary electron detectors; and (i) evaluating a pattern on the sample plane from a signal detected with the detector; wherein a cross-over to be formed by the electron gun for irradiating the plural apertures has a negative spherical aberration.