[labnetwork] Piranha processing vessels

[Robert M. HAMILTON]

Keith,

I'll stick my neck out!

The UC Berkeley NanoLab uses fused silica tanks with encased heaters and
ground-fault detection for our piranha baths. I am guessing your suggestion
of Pyrex or an alternative borosilicate glass will raise the hackles of
some Labnetwork readers. And, I cannot claim experience with the impact of
borosilicate glasses, used for piranha cleans, for MOS devices.

However, I can point to a patent issued to Alameda Instruments that made
H2SO4 reclaim/reprocessing systems for a number of major semiconductor
manufacturers. I also have known, since boyhood the research glassblower
who made their vacuum stills. The glass used was Pyrex or an alternative
Duran, which is Schott's equivalent. This leads me to the conclusion H2SO4
from a pyrex still was good enough for Intel, Pyrex is probably good enough
for you.

Having said this if there is accidental contamination via HF your Pyrex
will contribute alkali and your devices will be DOA. We have seen HF
contamination in our baths on a few occasions.

For reference see:  https://www.google.com/patents/US4980032

Bob Hamilton

PS Caveat emptor! Corning now uses the term Pyrex for a broader number of
glasses than their traditional 7740.


Robert Hamilton
University of CA, Berkeley
Marvell NanoLab Equipment Manager
Rm 520 Sutardja Dai Hall, MC 1754
Berkeley, CA 94720
Phone 510-809-8618 (desk - preferred)
Mobile 510-325-7557 (my personal mobile)
E-mail preferred: bob at eecs.berkeley.edu
http://nanolab.berkeley.edu/



On Thu, Apr 28, 2016 at 10:59 AM, Keith Franklin <keithf at ualberta.ca> wrote:

> Good day all,
>
> We're currently revisiting what vessels or tanks we use for processing
> with hot piranha.  Our most common application is for cleaning a partially
> filled cassette of 4" Si wafers.  We typically purchase Pyrex 6944 vessel
> and have our glass shop cut them down to a more reasonable height.  In our
> last purchase cycle, we noticed that the ID has changed ever so slightly
> and it's now challenging to squeeze our standard Entegris cassette into
> this vessel.  We're currently looking into custom machined PVC, PP,  Teflon
> & Quartzware, as well as off the shelf small volume tanks, etc.
>
> I'm hoping to better understand what other similar labs are using for this
> application (& potentially 6" wafers as well).  Any advice or feedback
> would be greatly appreciated.
>
> Kind Regards,
> Keith
>
>
> Keith Franklin
>
> Operations Manager
>
> University of Alberta - nanoFAB
>
> W1-060 ECERF Building
>
> 9107 - 116 Street
>
> Edmonton, Alberta
>
> Canada T6G 2V4 Ph: 780-492-0170
> www.nanofab.ualberta.ca
>
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