[labnetwork] Best practices for chemical storage, cross contamination, conservation

[Fouad Karouta]

Hi Michael,

Working with chemicals is a delicate matter and unless you have clear rules about what can be used in shared baths and what cannot. However this description may still be misinterpreted by users.

I am not sure if you have users using wet etchants for wafer batches (25x).
If users are only using one wafer to smaller pieces at one time you can limit the amount of chemicals used by having adequate containers to use a limited amount of chemical even with a one 4" wafer (beaker with 11 cm diameter and 5-6 cm edge height). For HF I tend to get regular size containers then get it machined in workshop to reduce the height.
Each user makes his solution and use it then dispose of it upon the rules (neutralize, etc.).
You may consider the following:

*         To avoid having every user preparing upfront those chemicals and putting a pressure on the storage area, you may consider having one container of each regularly used solution prepared and topped up by your staff, this can go for RCA, HF dilutions, etc.

*         A remark about piranha solution though I suppose the purpose is just cleaning the wafer but H2O2 is unstable in acidic solution and you should consider how long such a solution can be used.
Regards,
Fouad Karouta

*************************************
Manager ANFF ACT Node
Australian National Fabrication Facility
Research School of Physics and Engineering
L. Huxley Building (#56), Mills Road, Room 4.02
Australian National University
ACT 0200, Canberra, Australia
Tel: + 61 2 6125 7174
Mob: + 61 451 046 412
Email: fouad.karouta at anu.edu.au<mailto:fouad.karouta at anu.edu.au>
http://anff-act.anu.edu.au/

From: labnetwork-bounces at mtl.mit.edu [mailto:labnetwork-bounces at mtl.mit.edu] On Behalf Of Michael Khbeis
Sent: Saturday, 10 February 2018 11:19 AM
To: labnetwork at mtl.mit.edu
Subject: [labnetwork] Best practices for chemical storage, cross contamination, conservation

Dear Colleagues,

We have many users avoiding shared baths for things like RCA, Piranha, and even developers because they worry about cross-contamination (and rightfully so with random things floating in the baths on a fairly regular basis). However, this has led to numerous users pouring resealable, food grade containers, that subsequently leave them cluttered on our wet process station work surfaces for up to several weeks. This of course is not an acceptable solution but prohibiting this behavior will result in a massive waste of otherwise perfectly good chemicals. So we have a challenge of balancing process integrity, safety, and chemical economy. We are looking for better temporary storage solutions that would allow transport of containers to chemical cabinets, but I am curious how other sites have resolved or administered this issue.

Gratefully,

Dr. Michael Khbeis
Director, Washington Nanofabrication Facility (WNF)
National Nanotechnology Coordinated Infrastructure (NNCI)
University of Washington
Fluke Hall, Box 352143
(O) 206.543.5101
(F) 206.221.1681
(C) 443.254.5192
khbeis at uw.edu<mailto:khbeis at uw.edu>
www.wnf.washington.edu/<http://www.wnf.washington.edu/>

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