The present invention relates to a scanning electron microscope and calibration of a scanning electron microscope image distortion.
Miniaturization of semiconductor devices has recently been advancing more and more and geometrical dimensions need to be controlled more highly precisely. Under the circumstances, the dimension control using a scanning electron microscope is prevailing on the spot of semiconductor production. In the scanning electron microscope, however, a distortion called a scanning distortion takes place at the time that an electron beam is scanned using an electromagnetic deflector. Originally, a deflection magnetic field generated by the deflector of scanning electron microscope is uniform near the center but is not uniform at the edges, thus being the principal cause of a scanning distortion. Because of the non-linearity of the scanning signal, the dimension control by the scanning electron microscope is accompanied by errors. Then, JP-A-2000-48755 proposes method and apparatus for calibrating errors attributable to the scanning distortion. Specifically, the same site on the same specimen is observed at plural positions within the field of view of an electron microscope to measure the size. Results of sizes measured at the plural positions within the electron microscope view field are compared with one another and from the error in measurement result, the scanning distortion in the scanning electron microscope is measured.