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Ammonia Purge Process for a Plasma Reactor

IP.com Disclosure Number: IPCOM000034543D
Original Publication Date: 1989-Mar-01
Included in the Prior Art Database: 2005-Jan-27
Document File: 1 page(s) / 12K

Publishing Venue

IBM

Related People

Hlavka, JF: AUTHOR [+2]

Abstract

Anhydrous ammonia is a more effective purge gas for eliminating residual fluorine from plasma reaction chambers than is Freon 116 (C2F6). The standard etch gas used for cleaning silicon nitride deposits is Freon 116. The reaction between Freon 116 and silicon nitride produces fluorine compounds that remain in the reactor chamber after the etch is complete. Standard purge procedures are not always adequate for removing residual fluorinated compounds trapped on the walls of the plasma reactor chamber. This fluorine can be released as hydrofluoric acid vapor when the chamber is vented to the atmosphere. This poses a serious risk to personnel exposed to these vapors. Freon 116 and oxygen are used to etch silicon nitride from the walls of radio frequency (RF) plasma deposition reactors.

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Ammonia Purge Process for a Plasma Reactor

Anhydrous ammonia is a more effective purge gas for eliminating residual fluorine from plasma reaction chambers than is Freon 116 (C2F6). The standard etch gas used for cleaning silicon nitride deposits is Freon 116. The reaction between Freon 116 and silicon nitride produces fluorine compounds that remain in the reactor chamber after the etch is complete. Standard purge procedures are not always adequate for removing residual fluorinated compounds trapped on the walls of the plasma reactor chamber. This fluorine can be released as hydrofluoric acid vapor when the chamber is vented to the atmosphere. This poses a serious risk to personnel exposed to these vapors. Freon 116 and oxygen are used to etch silicon nitride from the walls of radio frequency (RF) plasma deposition reactors. Most of the reaction's by-products are volatile SiF, CO, and N radicals. Other by-products include fluorine radicals. It is these fluorine compounds that can adsorb to the aluminum oxide reactor walls and remain trapped. A standard multiple step nitrogen/vacuum purge is not able to remove trapped fluorine from the reactor walls. Trapped fluorine was still present in large quantities after 12 hours of vacuum purge. The ammonia purge process is six minutes long with an ammonia flow of 110 standard cubic centimeters (sccm), a nitrogen flow of 100 sccm at a process pressure of 600 millitorr. A 500- watt RF field is also applied to initiate the rea...