Mary Tang mtang at
Thu Feb 20 11:53:56 PST 2003

Hi all --

One of our staff members just witnessed a shocking event:  one of our
most experienced labmembers was transferring wafers out of a hot pot
into a dump rinser, and carrying labwipes underneath to catch acid
drips.  Needless to say, the labwipes were scorching black.  The
labmember's reponse was "everyone does this!"  I'm writing, because
everyone should NOT do this.

First safety issue:  the labwipes don't protect against acid exposure,
particularly if you're only wearing vinyl-over-latex gloves, as this
individual was doing.  Pirhana loves to eat organic materials, like
vinyl, latex and your skin.

Second safety issue:  Fire hazard.  Piranha and other strong oxidizing
acids will burn and possibly ignite organic materials, like labwipes.
Labwipes that are exposed to hazardous chemicals like piranha should be
disposed of properly as hazardous waste (double bagged, and labeled, in
yellow hazardous waste bags.)  They should not be placed in the trash --
this is like placing a smoking cigarette butt in the trash.  This also
unnecessarily exposes our custodial staff to chemical hazards.

The proper way to transfer wafers from a hot pot to a dump rinser
(paraphrasing from operating procedures):

1.  Open the dump rinse door.
2.  Lift the wafers out of the hot pot.  Hold them over the hot pot to
allow acid to drip off.
3.  Carry the wafers to the dump rinse and place them inside.  Let acid
drip on the wet bench deck.
4.  Close the dump rinse door and press "Start."
5.  Use the DI water gun to rinse off acid drips into the plenum.  (Do
not let acid drips sit on the deck.)
6.  Use the N2 gun to blow off excess water.
7.  Use wipes to clean off deck, if necessary (do not use wipes to clean
off unknown drips -- only water.)

Any questions, please contact your friendly neighborhood staff members.

Thanks for your attention --


Mary X. Tang, Ph.D.
National Nanofabrication Users' Network
Stanford Nanofabrication Facility
CIS Room 136, Mail Code 4070
Stanford, CA  94305
mtang at

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