Patent ID: 8013315
Filing Date: 2011-09-06
Classification: H01J

Abstract:
1. A charged particle beam apparatus for observing and estimating a sample by irradiating the sample with a charged particle beam to detect secondary charged particles such as electrons emitted from the sample, reflected electrons and backscattered electrons, said apparatus comprising an electro optical system which includes astigmatism adjusting means having a multipole for adjusting astigmatism of the charged particle beam, wherein said astigmatism adjusting means is supplied with a correction voltage which maximizes a value for adjusting focus obtained from an image of a pattern formed on said sample; and wherein said astigmatism adjusting means is operable to: (a) obtain a first pattern image including lines formed longitudinally and transversely on the sample; (b) adjust said electro optical system to obtain a first auxiliary voltage when the visibility of the longitudinal and transversal lines of the image becomes maximum; (c) apply the first auxiliary voltage to said multipole to adjust a cross section of the electron beam; (d) adjust said electro optical system while maintaining the first auxiliary voltage when the longitudinal line can been seen clearly to obtain a second auxiliary voltage when the visibility of the transverse line in the image becomes maximum; and (e) apply the second auxiliary voltage to said multipole to adjust the cross section of the electron beam so that a difference between the visibilities of the longitudinal line and the transverse line becomes minimum.