Measurement of fogging electrons present in scanning electron microscope specimen chamber

The purpose of this study is (1) to quantify the influence of fogging electrons, and (2) to find the conditions for reducing the amount in the vacuum specimen chamber of the electron beam instruments. Fogging electrons are generated on the surface of both the specimen and objective lens electrode and flies within the working distance. When a 100 mm sized copper electrode is used as a specimen and a bias voltage of -200 V to +200 V is applied to the specimen, the electron current flowing through the specimen or grounded objective lens electrode is measured with a pico-ammeter. The characteristics of fogging electrons can be interpreted by electron trajectory simulation. The fogging electron current at the specimen is minimal when the objective electrode is made of carbon, compared to when the electrode is made of aluminum, copper or stainless steel (SUS304).