Patent ID: 8692197

Claim:
A scanning electron microscope for measuring a pattern on a sample based on detection of electrons by scanning said sample surface with an electron beam, said scanning electron microscope comprising: a sample base to which a negative voltage is applied, said negative voltage being used for decelerating said electron beam which will attain to said sample; an opposite electrode for controlling an electric field which is generated on said sample; and a measurement device for: repeating measurements of dimensions at a plurality of measurement points on said sample, wherein an identical pattern is formed at each of said measurement points, and wherein said repeating is performed under each of a plurality of different electric-potential conditions between said sample base and said opposite electrode, and a calculation device for: determining a change over time of measurement values as a function of a number of completed measurements at said plurality of measurement points on said sample for each of said plurality of different electric-potential conditions, and based on said changes, calculating a voltage at which an inclination of said change of said measurement values under one of said plurality of different electric-potential conditions becomes equal to zero, or becomes close to zero, wherein said calculated voltage is applied to at least one of said sample base or said opposite electrode.