Patent ID: 7361896
Filing Date: 2008-04-22
Classification: H01J

Abstract:
1. A scanning electron microscope, comprising: an electron optic system having an electron source of electron beams, an electron lens for focusing said electron beams, so as to generate a focused electron beam, a deflection portion for deflecting an irradiation position of said focused electron beam within a view field, so as to irradiate the focused electron beam upon an observation target, an electron detector for detecting secondary electrons or reflecting electrons which are discharged from said observation target and converted into a signal, and a focal position controller for controlling a focal position of said focused electron beam; an AD converter/memory unit for converting the signal of the secondary electrons or the reflecting electrons detected by said electron detector of said electron optic system into a digital signal which is memorized into a memory; a view field moving unit for moving said electron optic system or an image-pickup target, relatively, so as to move the view filed, upon which said electron optic system picks up an image of said image-pickup target; a first electron beam irradiation controller portion for obtaining an intensity signal for use of calculating a focus-in position, through detecting the secondary electrons or the reflecting electrons obtained from a focus-in point at each of said focal positions by the electron detector of said electron optic system, irradiating the focused electron beam, being compensated scanning position thereof by compensating scanning position of said focused electron beam, through controlling said deflection portion depending upon an amount of movement of said view field, at each of the focal positions, while changing the focal position in a Z direction through controlling said focal position controller, under a condition of moving the view field for said electron optic system to pick up an image of said observation target by said view filed moving portion, and for convert it into the digital signal through said AD converter/memory unit, to be memorized into the memory; and a first focus-in position control variable calculating unit, having an analysis portion for calculating out a focus-in position through analyzing the intensity signal for use of calculating the focus-in position at each of the focal positions, which are memorized in said memory by means of said first electron beam irradiating position controller portion, and for calculating out a control variable of said focal position controller upon basis of the focus-in position which is calculated within said analysis portion, wherein said focal position controller is controlled upon basis of the control variable, which is calculated within said first focus-in position control variable calculating portion, so that an image is picked up of a predetermined region upon said image-pickup target through said electron optic system under a condition of being in focus.