Scanning electron microscope and method of imaging an object by using the scanning electron microscope

A scanning electron microscope comprising:

• a specimen-holding portion for holding a specimen;
• an electron beam source emitting an electron beam;
• a condenser lens for converging the electron beam emitted from the electron beam source;
• an electrode having an axisymmetric shape and mounted within a magnetic field produced by the condenser lens;
• an objective lens for focusing the converged electron beam into a very small spot onto the specimen;
• scan coils for scanning the electron beam over the specimen;
• a detector for detecting a specimen signal emanating from the specimen in response to the electron beam irradiation;
• means for applying a negative voltage to the specimen-holding portion to decelerate the primary electron beam;
• and
• a control unit for varying a focal position of the condenser lens without modifying the focus of the objective lens by varying the negative voltage applied to the specimen-holding portion while applying a given voltage to the electrode.

A method of imaging a candidate defect on a specimen and offering an image for observation or analysis by the use of a scanning electron microscope having a condenser lens for producing a focal position of the electron beam and a first electrode for varying the focal position of the electron beam by varying a voltage applied to the first electrode when an imaging magnification is modified, said method comprising the steps of:

• (a) extracting the candidate defect at a magnification at which the candidate defect is larger than the size of each pixel of the image, based on coordinates of one candidate defect among coordinates of plural candidate defects sent from an inspection system;
• (b) subsequently switching the magnification to a higher value and imaging the candidate defect;
• and
• (c) repeating the steps (a) and (b) for coordinates of the plural candidate defects.