Patent ID: 7189981

Claim:
A method for projecting a predetermined pattern of an electron beam from an emitter to a wafer in a vacuum chamber of an electron-beam lithography system, the method comprising: setting an initial condition for performing an electromagnetic focusing; correcting outspread phenomenon of the electron beam, which is caused by an initial emitting velocity difference and an initial emitting angle difference between electrons emitted from the emitter; correcting a shift of the electron beam, which is caused when an electric field is not in parallel with a magnetic field; correcting a shift of the electron beam, which is caused by a gradient of the magnetic field; correcting an increase of a beam diameter of the electron beam, which is caused by Coulomb-interaction force between the electrons emitted from the emitter; and determining if a focusing error is within a range of an allowable error and repeating, when it is determined the focusing error is out of the range of the allowable error, the above operations.