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Indirekt erhitzte Ionenquelle

Indirectly heated cathode ion source
Nummer: US 7138768 B2
Datum: 2002
Firma: Varian Semiconductors

When the ion source is in operation,
the filament 30 is heated resistively by filament current IF to thermionic emission temperatures, which may be on the order of 2200° C.
Electrons emitted by filament 30 are accelerated by the bias voltage VB between filament 30 and cathode 20 and bombard and heat cathode 20.
The cathode 20 is heated by electron bombardment to thermionic emission temperatures. Electrons emitted by cathode 20 are accelerated by arc voltage VA and ionize gas molecules from gas source 32 within arc chamber 14 to produce a plasma discharge

FIG. 7 is a perspective view of the indirectly heated cathode ion source of FIGS. 2A and 2B;

FIG. 8 is a schematic diagram that illustrates the electrical connection of the shield and the vacuum vessel in accordance with a first embodiment;

FIG. 1 is a schematic block diagram of an indirectly heated cathode ion source in accordance with an embodiment of the invention;

An indirectly heated cathode ion source includes an arc chamber housing that defines an arc chamber, an indirectly heated cathode and a filament for heating the cathode. The cathode may include an emitting portion having a front surface, a rear surface and a periphery, a support rod attached to the rear surface of the emitting portion, and a skirt extending from the periphery of the emitting portion. A cathode assembly may include the cathode, a filament and a clamp assembly for mounting the cathode and the filament in a fixed spatial relationship and for conducting electrical energy to the cathode and the filament. The filament is positioned in a cavity defined by the emitting portion and the skirt of the cathode. The ion source may include a shield for inhibiting escape of electrons and plasma from a region outside the arc chamber in proximity to the filament and the cathode.

This invention relates to ion sources that are suitable for use in ion implanters and, more particularly, to ion sources having indirectly heated cathodes.
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