Scanning electron microscope and sample observation method using the same

A scanning electron microscope comprising:

• an electron source;
• a first focusing lens for focusing a primary electron beam emitted from said electron source;
• an object lens diaphragm for removing an unnecessary region of the primary electron beam focused by said first focusing lens;
• a second focusing lens for focusing the primary electron beam that has passed through said object lens diaphragm;
• an object lens for focusing the primary electron beam focused by said second focusing lens on a sample;
• a deflecting means for the scanning of the sample by the primary electron beam;
• a secondary electron detector for detecting a secondary electron emitted from the sample due to electron beam irradiation;
• and
• an X-ray detector for detecting an X-ray emitted from the sample, wherein the exciting current of said object lens is set to prevent electrons reflected by the sample from reaching the X-ray detector;
• wherein said scanning electron microscope has a function of focusing the primary electron beam on the sample by using said object lens when the magnification of an image to be scanned is higher than a preset value (high-magnification mode),
• wherein said scanning electron microscope has a function of focusing the primary electron beam on the sample by using said second focusing lens when the magnification of an image to be scanned is lower than a preset value (low-magnification mode), and
• wherein, in said low-magnification mode, either a first low-magnification mode in which the exciting current of said object lens is set to be a constant value independently of the accelerating voltage of the primary electron beam or a second low-magnification mode in which the exciting current of said object lens is changed as a function of the accelerating voltage of the primary electron beam is selected.