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Improved Ion Source for Use With Reactive Ion Beams

IP.com Disclosure Number: IPCOM000040299D
Original Publication Date: 1987-Oct-01
Included in the Prior Art Database: 2005-Feb-02
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Cuomo, JJ: AUTHOR [+4]

Abstract

A technique is described whereby the life of hot cathode filaments is increased through a process which coats metal parts with a conductive metallic oxide. The resulting product is an improved ion source, for use with reactive ion beams. Kaufman ion sources are large-area ion sources used in material processing. When used with inert gases or reactive gases at relatively low power levels, they are very reliable. However, when used with reactive gases, such as oxygen at high power levels, the run time is limited. This is due to a build-up of insulating oxide layers on the anode of the source. This build-up of insulating oxide layer reduces the discharge current until the discharge is extinguished, when operated at a constant voltage.

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Improved Ion Source for Use With Reactive Ion Beams

A technique is described whereby the life of hot cathode filaments is increased through a process which coats metal parts with a conductive metallic oxide. The resulting product is an improved ion source, for use with reactive ion beams. Kaufman ion sources are large-area ion sources used in material processing. When used with inert gases or reactive gases at relatively low power levels, they are very reliable. However, when used with reactive gases, such as oxygen at high power levels, the run time is limited. This is due to a build-up of insulating oxide layers on the anode of the source. This build-up of insulating oxide layer reduces the discharge current until the discharge is extinguished, when operated at a constant voltage. Operating the discharge at higher voltages extends the ion source run time slightly; however, this causes increased sputtering inside the source and also may increase the number of multiple ionized species. When a large area anode, as in the Commonwealth ion source, is run with oxygen gas, oxygenation occurs throughout, not just on the surface. When a tungsten filament is used, at high power in oxygen, its lifetime is very short. The process described herein shows how the lifetime of the hot cathode filament can be increased by using thoria coated iridium filaments in place of other refractory metal filaments. Hot cathode filaments may also be coated with metallic oxide. A 1 mm thick ...