Scan type electron microscope

A scan type electron microscope comprising:

• an electron beam generating source for generating an electron beam with which a sample is irradiated;
• a vacuum chamber in which said electron beam passes;
• a sample chamber, for housing said sample, in communication with said vacuum chamber and supplied with gas for effecting gas amplification of secondary electrons emitted from said sample with the irradiation of said sample by said electron beam;
• secondary electron detecting means, installed at a connecting portion between said vacuum chamber and said sample chamber and including a pressure limiting aperture through which said electron beam passes, for detecting secondary electrons amplified by said gas;
• and
• an electrode, disposed between said sample and said secondary electron detecting means, for absorbing positive ions produced by the gas amplification of secondary electrons.

A scan type electron microscope comprising:

• an electron beam generating source for generating an electron beam with which a sample is irradiated;
• a vacuum chamber in which said electron beam passes;
• a sample chamber for housing said sample and in communication with said vacuum chamber via a pressure limiting aperture through which said electron beam passes, said sample chamber being supplied with gas for effecting gas amplification of secondary electrons emitted from said sample with the irradiation of said sample by said electron beam;
• secondary electron detecting means, installed in said sample chamber, for detecting secondary electrons amplified by said gas;
• and
• a fine tube electrode for absorbing positive ions produced by the gas amplification of secondary electrons and through which said electron beam passes from said pressure limiting aperture to said sample, said fine tube electrode being extended from said pressure limiting aperture substantially to said sample;
• and
• means for maintaining said fine tube electrode at a predetermined electrical potential.