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Foreline Trap for Removal of Hydrocarbon Vapors

IP.com Disclosure Number: IPCOM000083442D
Original Publication Date: 1975-May-01
Included in the Prior Art Database: 2005-Mar-01
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Coburn, JW: AUTHOR

Abstract

Various types of vacuum operations are performed in the pressure regime compatible with the operation of a glow discharge (e.g., sputtering, plasma polymerization, gas discharge lasers). A problem associated with pumping these vacuum systems directly with a mechanical pump, is the pump oil vapors (primarily hydrocarbons) backstreaming from the pump to the vacuum system. In-line zeolite and LN traps are used to alleviate this problem, but are not very effective in trapping low-molecular weight, high-vapor pressure species such as methane.

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Foreline Trap for Removal of Hydrocarbon Vapors

Various types of vacuum operations are performed in the pressure regime compatible with the operation of a glow discharge (e.g., sputtering, plasma polymerization, gas discharge lasers). A problem associated with pumping these vacuum systems directly with a mechanical pump, is the pump oil vapors (primarily hydrocarbons) backstreaming from the pump to the vacuum system. In-line zeolite and LN traps are used to alleviate this problem, but are not very effective in trapping low-molecular weight, high-vapor pressure species such as methane.

It has been found that the concentration of an organic species in an inert gas is greatly reduced, when a very modest (10 ma) glow discharge is established. The final disposition of the organic material is believed to be in the form of a polymeric deposit on the walls of the discharge chamber. It is proposed that this pumping action of a discharge for organic molecules be used as a trap in the vacuum line between a mechanical pump and a vacuum system which typically operates in the high-pressure regime, thus enabling the relatively low-cost, high- throughput mechanical pump to be used to pump the system with a large reduction in hydrocarbon contamination.

The constructional detail of the trap can range from a section of glass tubing in the vacuum line encircled by several turns of an RF excited coil, to a more elaborate setup with internal electrodes. The following guidelines should...