US Patent 10014153 Electron microscope and method of aberration measurement

There is provided an electron microscope capable of measuring aberration with high accuracy. The electron microscope (100) comprises: an electron beam source (10) for producing an electron beam (EB); an illumination lens system (101) for focusing the electron beam (EB) onto a sample (S); a scanner (12) for scanning the focused electron beam (EB) over the sample (S); an aperture stop (30) having a plurality of detection angle-limiting holes (32) for extracting rays of the electron beam (EB) having mutually different detection angles from the electron beam (EB) transmitted through the sample (S); and a detector (20) for detecting the rays of the electron beam (EB) passed through the aperture stop (30).