[labnetwork] TMAH vs KOH

[Mary Tang]

Hi Matthieu --

This isn't really an answer, but your question brings up a paper that a 
former SNF labmember sent to us from Clinic Toxicology, 48, p. 213 
(2010) entitled: "Tetramethyl ammonium hydroxide poisoning".  It 
describes tetramethylammonium as a well-documented, non-specific nerve 
agent (a ganglionic blocker).  As a positive ion, it doesn't normally 
pass through skin very well, but in its hydroxide form, the corrosive 
damage to the skin allows it to pass easily into the body.  The paper 
documents several clinical cases of exposure to TMAH solutions -- in two 
lethal cases, the victims were exposed to 25% TMAH covering 7% of their 
body surface area for < 1 min.  Significant health effects were observed 
in exposures to 2.38% TMAH for 10 minutes or less.

The MSDS for TMAH at first glance looks just a tad scarier than KOH but 
no mention that it is a nerve agent.  Both are listed as severe poison, 
but I'm guessing that similar exposures to KOH would not be as lethal.

We now treat TMAH with much greater respect, not only for silicon 
etching, but for resist developers as well (with typical concentrations 
of 2.3%.)

Mary



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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