Patent ID: 7129485

Claim:
A method of evaluating a sample, using an electron beam apparatus comprising: preparing a plurality of standard marks having different line and space patterns; selecting one of standard marks, which has a line and space pattern corresponding to a width of a line on the sample to be evaluated; irradiating the selected standard mark with a plurality of electron beams having different diameters at a plurality of times, respectively; detecting secondary electron beams emitted from the selected standard mark at the respective irradiation times to evaluate S/N ratios; selecting a diameter from the different diameters of the irradiated electron beams, with which a maximum S/N ratio has been obtained in the S/N ratio evaluation; irradiating said sample with a primary electron beam having the selected beam diameter; detecting a secondary electron beam generated from the sample by the irradiation; and evaluating the sample, wherein said electron beam apparatus comprises: an electron gun having a cathode for forming a primary electron beam; a lens positioned near said electron gun; a beam separator for separating said secondary electron beam from a primary electro-optical system and directing it to a secondary electron detector; and an objective lens for accelerating said secondary electron beam emitted from the sample, wherein said beam separator is positioned above said objective lens so that the secondary electron beam passes though said objective lens and then is deflected and separated from said primary electro-optical system without entering a second lens from the sample surface.