Small electron gun

Abstract

To provide a small electron gun capable of keeping a high vacuum pressure used for an electron microscope and an electron-beam drawing apparatus. An electron gun constituted by a nonevaporative getter pump, a heater, a filament, and an electron-source positioning mechanism is provided with an opening for rough exhausting and its automatically opening/closing valve, and means for ionizing and decomposing an inert gas or a compound gas for the nonevaporative getter pump. It is possible to keep a high vacuum pressure of 10 −10 Torr without requiring an ion pump by using a small electron gun having a height and a width of approximately 15 cm while emitting electrons from the electron gun.

1 . An electron gun comprising: 
 an electron source;    a vacuum vessel holding the electron source;    a getter pump attached inside the vacuum vessel;    an opening configured to roughly exhaust the vacuum vessel;    a heating device configured to heat the getter pump; and    a decomposing device configured to decompose the gas produced while the electron source operates.