[labnetwork] KOH/IPA Solution

[Dan Woodie]

Michael,

At the CNF, we do not allow IPA on KOH due to the fire hazard (flash point of IPA is about 11 - 13 deg C, well below even room temp). Instead of using IPA, we offer Triton X-100, an anionic surfactant that can be added to many etching solutions. We pursued that after users started requesting many of the common etching solutions we used in surfactant variations. Trying to avoid every combination of surfactant and regular solutions on the shelf, we looked for something that could be added to most solutions if desired. The challenge with most surfactants is getting the correct concentration, which is usually very low. For the Triton X-100, I found a publication that pointed towards 100 ppm as the optimum concentration. So, we predilute the material down to a dilute solution in an eye dropper style dispenser, labeled to show the proper number of drops to add per liter of etching solution, and warning that more is not better for surfactants.

I don't have definitive information on how well it does versus IPA, but for both BOE solutions and KOH, I have had positive verbal feedback from researchers.

Dan

Daniel Woodie
Safety Manager, College of Engineering
Cornell University
344 Duffield Hall
Ithaca, NY 14853-2700
(607)254-4891
Off Hour Emergency # - (607)227-2993

From: labnetwork-bounces at mtl.mit.edu [mailto:labnetwork-bounces at mtl.mit.edu] On Behalf Of Michael Khbeis
Sent: Friday, June 22, 2012 11:29 AM
To: Fab Network
Cc: Andrew R. Lingley
Subject: [labnetwork] KOH/IPA Solution

Good Morning,

We have just replaced all of our wet processing stations and are setting up a 6L recirculating bath of KOH w/ ~20% IPA as a surfactant.  I am presuming that the IPA will readily evaporate and will not pose a regulatory issue with dumping to waste water treatment.  I was wondering if most of you still use IPA or have moved to other surfactants for Si preferential wet etch.  If you still use IPA how do you handle the effluent?

I appreciate the fab knowledge support community that you all contribute to.

Gratefully,

Dr. Michael Khbeis
Associate Director
Microfabrication Facility (MFF)
University of Washington
Fluke Hall, Box 352143
(O) 206.543.5101
(C) 443.254.5192
khbeis at uw.edu<mailto:khbeis at uw.edu>

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