Patent ID: 9035550
Filing Date: 2015-05-19
Classification: H01J

Abstract:
1. A method of making axial alignment of a charged particle beam by a charged particle beam system having an astigmatic correction lens including a first pair of coils and a second pair of coils, the first pair of coils consisting of first and second coils which are located on opposite sides of the axis of the charged particle beam, the first and second coils having opposite coil surfaces having magnetic poles of a first polarity, the second pair of coils consisting of third and fourth coils which are located on opposite sides of the axis of the charged particle beam, the third and fourth coils having opposite coil surfaces having magnetic poles of a second polarity different from the first polarity, the second pair of coils being angularly spaced from the first pair of coils, said method comprising the steps of: obtaining first to sixth sets of image data while varying currents flowing through the first to fourth coils according to first to sixth sets of conditions; and then calculating the values of the currents through the first to fourth coils for correcting the position of the axis of the charged particle beam passing through the astigmatic correction lens based on the first to sixth sets of image data, wherein electric current J flowing through each of the first to fourth coils is the sum I+i(J=I+i), where I is a first component of the current J for correcting astigmatism and i is a second component of the current J for correcting the position of the axis of the charged particle beam; wherein under the first set of conditions, the first components (I's) through the first to fourth coils are equal to each other and equal to a given current value I wherein under the second set of conditions, the first components (I's) through the first to fourth coils are equal to each other and equal to a current value I wherein under the third set of conditions, the first components (I's) of the first to fourth coils are equal to the given current value I wherein under the fourth set of conditions, the first components (I's) through the first to fourth coils are current value I wherein under the fifth set of conditions, the first components (I's) through the first to fourth coils are the given current value I wherein under the sixth set of conditions, the first components (I's) through the first to fourth coils, respectively, are current value I