Electrostatic charge measurement method, focus adjustment method, and scanning electron microscope

A scanning electron microscope comprising an electron source, a scan deflector for scanning an electron beam emitted from the electron source on a sample, a detector for detecting secondary electron emission obtained based on the electron beam scanning on the sample;

• an energy filter for performing energy filtering on the secondary electron emission from said sample;
• and a control device for controlling an application, voltage to the energy filter;
• wherein
• said control device is configured to apply different voltages to said energy filter for every electron beam irradiation while shifting the beam to a different location with respect said sample to detect change in quantity of said detected secondary electron emission with respect to change in the application voltage to said energy filter, and to calculate an electrostatic charge amount of said sample or the application voltage applied to said sample based on said application voltage where a predetermined detection electron quantity has been obtained.

A method of adjusting a focus of an electron beam on the basis of detected secondary electron comprising:

• scanning an electron beam on a sample whose surface becomes electrostatically charged;
• arranging an energy filter for energy filtering secondary electron emission from said sample;
• acquiring a reference curve based on another sample whose surface is free of an electrostatic charge;
• applying different voltages to said energy filter for every electron beam irradiation while shifting the beam to a different location on said sample to form a curve indicating a change in quantity of said detected secondary electron emission with respect to change in application voltage to said energy filter;
• and
• the formed curve and the acquired curve are compared to calculate a negative voltage to be applied to said sample.