[labnetwork] Piranha processing vessels

[Keith Franklin]

Thank you all for the feedback.  Very helpful!  Please keep them coming
should anyone else be willing to contribute.

Best,
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

On Fri, Apr 29, 2016 at 7:29 AM, Mary Tang <mtang at stanford.edu> wrote:

> Thanks Bob!
>
> A wonderful example of how "contamination" can be managed by means other
> than the paranoia -- something we struggle with as we try to serve a
> broader community while trying to keep our electronics and detector
> researchers happy.  I would hazard a guess that this works in industry
> because distillation is vacuum rather than heated and that an additional
> RCA-equivalent clean is used before high temperature processing steps, thus
> minimizing the risk of driving in mobile ions.
>
> That said, at Stanford, we do promote paranoia when it comes to dedicated
> teflon cassettes in MOS stations because of their propensity to absorb
> whatever chemical they are exposed to.  I've not seen any data that shows
> cross-contamination due to this, but have seen the results of off-gassing
> on wafers stored or heated in chemical bath cassettes.  The risk of
> significant carryover of HF into piranha may be very low, but might be
> worth considering dedicated cassettes when using pyrex.
>
> Mary
>
>
> --
> Mary X. Tang, Ph.D.
> Stanford Nanofabrication Facility
> Paul G. Allen Bldg 141, Mail Code 4070
> Stanford, CA  94305(650)723-9980mtang at stanford.eduhttp://snf.stanford.edu
>
>
>
> On 4/28/2016 1:21 PM, Robert M. HAMILTON wrote:
>
> 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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>>
>
>
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