[labnetwork] TMAH vs KOH

[Robert M. Hamilton]

Matthieu Nannini,

At the Berkeley NanoLab we support both KOH and TMAH use at 
a dedicated work process station. We have not had issues 
with these processes. Having said this, we have added the 
following caution statement about TMAH exposure to our lab 
and safety manuals after our Office of Environmental Health 
& Safety shared data about fatal TMAH exposures in Taiwan:

"TMAH (Tetramethylammonium hydroxide) is widely used as a 
photoresist developer (2-3%) and for the anisotropic etching 
of silicon (10-15%). TMAH is a strong base and hazardous by 
ingestion, inhalation, skin (dermal) exposure and eye 
contact. In addition to alkalinity-related chemical burn, 
dermal exposure to TMAH may also result in respiratory 
failure and/or cardiac arrest. A 2010 study of case reports 
of Taiwan semiconductor factory injuries linked exposure of 
25% TMAH to three cases of heart failure. It is important to 
treat TMAH skin exposure by flooding the effected area with 
water for at least 15 minutes and to report all exposures."

More generally, caustic burns (KOH or TMAH) can be worse 
than acid burns. It is difficult to cleanse the orbit of an 
eye when exposure occurs and caustic quickly penetrate 
tissue. While 15 minutes may seem an inordinate amount of 
time for a topical exposure to a chemical, trauma 
specialists who we've consulted tell us such long rinses 
have definite value.

Sincerely,
Bob Hamilton

Robert M. Hamilton
Marvel NanoLab
University of CA at Berkeley
Rm 520 Sutardja Dai Hall
Berkeley, CA 94720-1754
bob at eecs.berkeley.edu
(e-mail preferred)
510-809-8600
510-325-7557 (Emergencies)


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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