[labnetwork] TMAH vs KOH

[David A. Bunzow]

Hello Mattieu,
IMHO, from a health perspective, TMAH appears far more dangerous than KOH.  We
recently prepared a lab-wide notification concerning TMAH and its known but often
overlooked dangers based on skin adsorption as opposed to ingestion as an 
identified
route of exposure.

"Materials Safety Bulletin
September 24, 2010

TMAH: New Hazard Awareness Concerning an Old Chemical
Tetramethylammonium hydroxide (TMAH) is widely used in micro- or nanofabrication
as an etchant and developer. In MSD, TMAH is typically one of several 
ingredients in
commercial etching/stripping mixtures, although it may also be used as a pure 
chemical.

While it has long been known to be very toxic if ingested, recent industrial 
experience
indicates that skin exposure may result in serious injury/illness or even death. 
Since 2007,
there have been 3 recorded fatalities from skin exposure to TMAH solutions as 
dilute as
25%. Two of the recorded fatalities occurred due to heart attack despite immediate
decontamination and prompt medical care. Thus skin, exposure to >1% TMAH over a
few percent of the body must be treated as a life-threatening event. MSDSs may 
be out of
date and not properly describe this high dermal toxicity.

When handling this material, the minimum set of personal protective equipment 
includes:
safety goggles (not glasses), disposable nitrile gloves, a buttoned lab coat, 
leg covering and
closed-toe shoes. The disposable gloves may only provide brief protection and 
must be
replaced if they become wetted. More protective gloves are the Stansolv or 
Tri-Ionic glove
models sold by MAPA.

In the event of a splash, contaminated clothing must be removed and the wetted area
thoroughly washed with soap and water, using the emergency shower if necessary.
Call 911 and summon emergency medical help.

You should not handle TMAH containing materials when working alone.
Tri-Ionic clean room gloves provide excellent protection from TMAH exposure."


David A. Bunzow
User Facilities Program Manager
The Molecular Foundry
Materials Science Division
Lawrence Berkeley National Laboratory
1 Cyclotron Road        MS 67-3207
Berkeley, CA   94720

Office:  510-486-4574
FAX:  510-486-7424
Cell:  701-541-2354


On 5/18/2011 9:20 AM, Matthieu Nannini, Dr. wrote:
> Dear all,
>
> Having only one base dedicated bench running TMAH @ 85C I have now to make a choice between TMAH and KOH since new researcher are asking for KOH. Maintaining the 2 chemicals requires resources that I don't have.
> Process wise, TMAH is better with oxide masks but KOH is better with SiN masks. KOH also etches faster and nicer.
> My questions are in terms of safety: could you share your experiences with KOH vs TMAH in terms of ease of use, safety, etc...
>
> Thanks
>
> -----------------------------------
> Matthieu Nannini
> McGill Nanotools Microfab
> Manager
> t: 514 398 3310
> c: 514 758 3311
> f: 514 398 8434
> http://miam2.physics.mcgill.ca/
> ------------------------------------
>
>
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