Electron beam excited ion source

Abstract

An ion source according to the present invention includes a first chamber, including a main chamber having an electron generating arrangement therein, and a sub-chamber communicating with the main chamber through a nozzle, for producing a first plasma by a discharge. A supply is also provided for supplying a first gas for a discharge into the main chamber, as well as an electron extracting arrangement for extracting electrons from the first plasma. Also included are a second chamber for producing a second plasma by discharge excitation of the extracted electrons and ionizing a second gas as a source gas, a further supply for supplying the second gas into the second chamber, and a magnetic field generator for generating a magnetic field for guiding the extracted electrons toward the second chamber. The electron extracting arrangement includes an electrode between the sub-chamber and the second chamber. The electrode has a first hole, formed at a position opposite to the opening of the nozzle, for allowing the extracted electrons to pass therethrough and to move into the second chamber, and second holes, arranged around the first hole, for allowing part of the first gas injected from the nozzle to pass therethrough and to move into the second chamber. Part of the first gas is drawn into the second chamber through the second holes of the electrode, and the density of the first gas passing through the first hole is decreased.