[labnetwork] TMAH controls or substitutes

[Mac Hathaway]

Hi Linda,

At Harvard CNS we only allow 25% TMAH usage in the dedicated "strong" 
acid/base benches, with full PPE at all times (extra chemical gloves, 
poly chemical apron with sleeves, faceshield, safety glasses).  We are 
trying to phase it out.  For Si etching, we encourage the use of KOH 
instead.

For 2.5-3.0% (i.e. MIF developer), we are not as rigorous, but we are 
reviewing that PPE as well.

For those who are not familiar with TMAH, it has been recently 
re-appraised by groups in Taiwan, IBM, and elsewhere, in light of the 
discovery that, in a small sample of people who had exposures to either 
25% and 3% TMAH, 3 out of the 4 exposed to 25% TMAH died, one of whom 
reportedly got under a safety shower within 30 seconds (he still 
died.).  The minimum exposed area in the review was, I believe, 7.5% 
body area exposed.  Toxicity appears unrelated to, but exacerbated by 
the extreme caustic nature of the material.  The current bottom line is 
25% TMAH appears to be a potent neurotoxin, and there is no known 
antidote.   The reason this is a problem is that TMAH is the active 
ingredient in most "metal-ion-free" developers, although this is only in 
the ~3% concentration, where neurotoxicity is much reduced, and 
manifests itself in lessor symptoms like tingling, blurred vision, etc.  
25% TMAH is used in Si etching, and for some E-beam resist purposes, as 
a developer for HSQ.


Mac Hathaway
Safety Officer
Harvard CNS


On 9/4/2012 2:06 AM, Linda Macks wrote:
>
> Hi all,
>
> We are currently reviewing our processes using TMAH, and I would be 
> grateful for any feedback re. safety controls or substitute chemicals, 
> particularly for Si etching involving 25% concentration TMAH.
>
> Many thanks,
>
> Linda
>
> *Dr Linda Macks*
> Facility Manager, ANFF-NSW
> Australian National Fabrication Facility
> School of Electrical Engineering & Telecommunications
> University of New South Wales
> UNSW Sydney NSW 2052
> Australia
> Phone: +61 (2) 9385 7845
> Fax: +61(2) 9385 5114
> Email: linda.macks at unsw.edu.au <mailto:linda.macks at unsw.edu.au>

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