Browse Prior Art Database

Device Stopping the Backdiffusion of Water Vapor

IP.com Disclosure Number: IPCOM000100805D
Original Publication Date: 1990-Jun-01
Included in the Prior Art Database: 2005-Mar-16
Document File: 1 page(s) / 34K

Publishing Venue

IBM

Related People

Preisser, R: AUTHOR

Abstract

The device, inserted in a gas line, eliminates the backdiffusion of water vapor by means of a semipermeable membrane, with the water vapor being adsorbed in a desiccator.

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Device Stopping the Backdiffusion of Water Vapor

       The device, inserted in a gas line, eliminates the
backdiffusion of water vapor by means of a semipermeable membrane,
with the water vapor being adsorbed in a desiccator.

      A reaction tube 1 (illustrated in the figure) for thermally
oxidizing silicon wafers is connected to lines carrying water vapor
(H2O), oxygen, nitrogen and hydrogen chloride (HCl).  When the HCl
supply is cut off, H2O vapor tends to backdiffuse into the HCl line
which, since it preferably consists at least partly of stainless
steel, is corroded by the mixture of HCl/H2O.  This is prevented by
inserting a device 2 between tube 1 and the stainless steel part of
the HCl line.  Device 2 consists of a gas line 3, which is part of
the HCl line, and of a semipermeable membrane 4, as well as of a
tubelike envelope 5 for gas line 3 closed on both sides.  The ends of
envelope 5 are connected by a thin tube 6 including a pump 7 and
desiccator 8.  H2O vapor entering gas line 3 from reaction tube 1
penetrates membrane 4 to be carried away from the other side of the
latter by a dry air stream.  This dry air stream is circulated
through envelope 5 and tube 6 and forced through desiccator 8 by pump
7, thus preventing the H2O vapor from further backdiffusing into the
HCl line.