Ammonium Fluoride Crystals at wet benches
mtang at stanford.edu
Fri Mar 2 18:33:51 PST 2007
We have got a serious problem! Large clumps of ammonium fluoride
crystals have been observed on several wet benches (wbgen2, wbdiff,
wbnonmetal, and wbmetal). These crystals have been found on the
benchtops, on top of the dump rinser lids, on the side splash shields,
on TOP of the upper splash shield, and down the front of one bench
continuing to the floor. This appears to be happening during the night,
since these crystals are found in the morning. This was first observed
and has been observed yesterday morning and this morning. We are
presuming that someone or some people are extraordinarily sloppy in
their handling of HF-BOE etchants.
Just to remind everyone -- ammonium fluoride is as bad for you as HF
because as soon as it hits moisture (like on your skin), it turns into
HF which is readily absorbed through your skin and evaporates so you can
inhale it. For your reference, here's a section from the JT Baker MSDS
for BOE etchants and ammonium fluoride.
*Skin Contact:* Wipe off any excess material from skin and then
immediately flush skin with large amounts of soapy water. Remove
contaminated clothing and shoes. Wash clothing before re-use. Apply
bandages soaked in magnesium sulfate. CALL A PHYSICIAN IMMEDIATELY.
*Label Hazard Warning:* DANGER! MAY BE FATAL IF SWALLOWED OR INHALED.
AFFECTS RESPIRATORY SYSTEM, HEART, SKELETON, CIRCULATORY SYSTEM, CENTRAL
NERVOUS SYSTEM AND KIDNEYS. CAUSES IRRITATION AND BURNS TO SKIN, EYES
AND RESPIRATORY TRACT. IRRITATION AND BURN EFFECTS MAY BE DELAYED.
HARMFUL IF ABSORBED THROUGH SKIN.
I hope everyone is as mad about this as I am.
On behalf of the SNF staff, I'm asking you the following:
- Be observant when you are in the lab. Report any problems to staff.
But don't be afraid to tell someone when you uncomfortable with their
lab procedure -- this is your safety they are risking too!
- . Be careful using the wet benches. Treat any liquid as if it were
acid (as it very well may be!) Treat crystals as if they were acid
(because they will be!) Leave the bench space clean when you leave it.
In the meantime, we are continuing to investigate. If you have any
observations or suggestions to share, please don't hesitate to drop us a
Mary X. Tang, Ph.D.
Stanford Nanofabrication Facility
CIS Room 136, Mail Code 4070
Stanford, CA 94305
mtang at stanford.edu
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