Patent ID: 8742343

Claim:
A method of making axial alignment of a charged particle beam in a charged particle beam system having a first alignment coil for deflecting the beam in a first direction, a second alignment coil for deflecting the beam in a second direction crossing the first direction and an objective lens for focusing the beam onto an object, and operating to adjust the axis of the beam by means of the first and second alignment coils, to detect a signal emanating from the object and to obtain image data, said method comprising the steps of obtaining at least first to third sets of image data by scanning the beam on a scanning area including a shielded region and repeating the scanning while varying conditions of excitation currents flowing through the first and second alignment coils, respectively; and calculating the values of the excitation currents through the first and second alignment coils, respectively, for axial alignment of the beam based on the obtained first to third sets of image data, wherein during the step of obtaining the at least first to third sets of image data, the first set of image data is obtained under conditions where the value of the excitation current through the first alignment coil is a first current value and where the value of the excitation current through the second alignment coil is a second current value, the second set of image data is obtained under conditions where the value of the excitation current through the first alignment coil is the first current value and where the value of the excitation current through the second alignment coil is a current value obtained by varying the second current value by a second incremental amount of current, and the third set of image data is obtained under conditions where the value of the excitation current through the first alignment coil is a current value obtained by varying the first current value by a first incremental amount of current and where the value of the excitation current through the second alignment coil is the second current value.