Browse Prior Art Database

Device for Avoidance of Pollutants from Wet-Chemical Processes

IP.com Disclosure Number: IPCOM000106421D
Original Publication Date: 1993-Nov-01
Included in the Prior Art Database: 2005-Mar-21
Document File: 2 page(s) / 64K

Publishing Venue

IBM

Related People

Thiele, M: AUTHOR

Abstract

This article describes a way of removing pollutants from the cleaning solutions used in the production of magnetic heads.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 55% of the total text.

Device for Avoidance of Pollutants from Wet-Chemical Processes

      This article describes a way of removing pollutants from the
cleaning solutions used in the production of magnetic heads.

      When fabricating thin-film magnetic heads, a basic solution
with a chelating agent, like EDTA, is used as an etch bath.  EDTA is
a very strong complexing agent for heavy metal ions but it might as
well accumulate in the environment.

      During the normal life time of an etch bath (appr.  4 weeks), a
considerable amount of EDTA is lost because of drag-out processes.
This amount of EDTA can be found in the rinse water and the rinse
tank.  The huge amount of waste water and its pH will only allow a
few ions to get complexed with EDTA.  But if there is a chance of
EDTA accumulation outside the plant site, this amount has to be
decreased to zero.

      The Figure shows the way this can be achieved.  The new
features can be added to existing layouts and only a few new pipes
have to be added:

      The wafer boat is transported after each etch cycle to the
spray rinse tank and an electrical sensor starts the rinse program,
which can be changed easily to accomplish several needs.  For the
first 15 seconds approximately 10 liters of rinse water are sprayed
over the boat and the wafers.  This volume carries 99.9% of the EDTA
drag-out.  It should be seperated with an electrical valve which
opens the pipe to a reservoir for 15 seconds.  Another sensor is
act...