Browse Prior Art Database

Ammonium Hydroxide Clean for Hazardous Exhaust Scrubbers

IP.com Disclosure Number: IPCOM000109044D
Original Publication Date: 1992-May-01
Included in the Prior Art Database: 2005-Mar-23
Document File: 1 page(s) / 63K

Publishing Venue

IBM

Related People

Curry, MR: AUTHOR [+3]

Abstract

Low pressure chemical vapor deposition (LPCVD) is used as a means of depositing tungsten metal onto silicon wafers to connect various metal levels to one another. The LPCVD tungsten process uses as reactant gases, tungsten hexafluoride (WF6), silane (SiH4) and hydrogen (H2) to form metallic tungsten on silicon wafers. The product of these reactants can form compounds that foul exhaust scrubbing equipment used to purify the process effluent. Ammonium hydroxide can be used to treat the scrubber system to maintain clean operation of the scrubber system.

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Ammonium Hydroxide Clean for Hazardous Exhaust Scrubbers

      Low pressure chemical vapor deposition (LPCVD) is used as a
means of depositing tungsten metal onto silicon wafers to connect
various metal levels to one another.  The LPCVD tungsten process uses
as reactant gases, tungsten hexafluoride (WF6), silane (SiH4) and
hydrogen (H2) to form metallic tungsten on silicon wafers.  The
product of these reactants can form compounds that foul exhaust
scrubbing equipment used to purify the process effluent.  Ammonium
hydroxide can be used to treat the scrubber system to maintain clean
operation of the scrubber system.

      The reactant gases enter a 450 deg C reaction chamber where the
WF6 is decomposed to tungsten and hydrogen fluoride.  This process is
done under a vacuum at 80 torr. Some of the WF6 remains unreacted
through the reactor and the associated pumping system.  The unreacted
WF6 then is discharged into a spray-type water scrubber designed to
trap the hydrogen fluoride and unreacted WF6.  The unreacted WF6
reacts with the water in the scrubber to form tungsten oxide (WO3).
Tungsten trioxide is a yellow-colored solid that is insoluble in
water.

      The tungsten trioxide plugs the water scrubber spray nozzles,
filter screens, and side walls.  The scrubber becomes ineffective and
potentially dangerous if the deposits are allowed to build up.  The
tungsten oxide is almost impossible to remove with standard hand-
scrubbing with cloth or 3M Corp....