[Fwd: Re: Hydrobromic Acid at Wetbench General]

Mary Tang mtang at stanford.edu
Fri Aug 6 13:19:55 PDT 2010

Hi all --

I guess the halogen passivation process is being investigated again.  
This is what Jungyup did, I believe.

I don't like this process, but also can see it would be OK to run with 
appropriate warnings and precautions.  The first is reinforcing use of 
protective gear.  Second, is ensuring that no oxidizers are used at this 
bench while work is being done -- maybe best to ensure that the whole 
bench is reserved and blocked off (Uli has procedures for approved 
processes) and never left unattended.  The other concern is how to blow 
48% HBr off a wafer without contaminating on nearby surfaces.

I would suggest reviewing this step-by-step with Jason.  And making it 
clear that anyone else who does this needs to specially trained as well.

What does everyone else think?  Uli?


-------- Original Message --------
Subject: 	Re: Hydrobromic Acid at Wetbench General
Date: 	Thu, 5 Aug 2010 16:51:15 -0700
From: 	J. Jason Lin <jasonlin at stanford.edu>
To: 	Mary Tang <mtang at stanford.edu>
<31624_1281048589_4C5B4009_31624_448_1_AANLkTinHgV3=L4+DRK5DHvS1rwL4FUNtyF_WoTQghS0V at mail.gmail.com> 
<4C5B435C.8040406 at stanford.edu>

Hi Mary,

It seems JT Baker sells HBr acid in 500mL container, so maximum I would 
bring in would be 500mL.  Since I don't need that much per run (mostly 
processing pieces) I am trying to find a place to buy smaller quantities.

I'll be trying the process with HBr once to see if it works, but if it 
can give me good results, then it may become a more regular occurrence.

The process I plan to use is to do the standard Ge clean at the 
germanium wetbench.  Then move to wbgen and dip my pieces into HBr for 
10 minutes and blow dry with N2 gun.  I would then immediately transfer 
them to the ALD chamber.  No other chemicals will be at wbgen and HBr 
will be at room temperature.  I've attached the paper where this was 
done.  Also, the process is the same as used by Jungyup Kim here a few 
years ago when he was exploring how to clean Ge.  In his case, he used 
HF, HCl, HBr, and HI to passivate the Ge surface by dipping Ge pieces 
into one of those acids for 2 minutes.

With regards to the incompatibilities of HBr, I will be using dedicated 
teflon tweezers and labware.  The pieces themselves will only have Si, 
Ge, and SiO2, so no metals there either.  What kind of special 
procedures should I adopt while working at wbgeneral?  If there are 
established procedures then I can follow those; otherwise, I can reserve 
both wbgen-hpr and wbgen-ctb and put up a sign informing other users not 
to use the wbgeneral while I am using HBr.


On Thu, Aug 5, 2010 at 4:03 PM, Mary Tang <mtang at stanford.edu 
<mailto:mtang at stanford.edu>> wrote:

    Hi Jason --

    More detail on your procedure would be appreciated.  HBr protocols
    are reviewed very carefully.

    1.  How much HBr do you plan to bring in and store?
    2.  Is this one time or will you be doing this often?
    3.  Do you have a detailed procedure from a reference that you are
    using?  Are there other chemicals involved?
    4.  Please be aware incompatibilities of HBr.  This includes metals
    (so, no metal tweezers) and strong oxidizers (which are allowed at
    wbgeneral.).  You would need to use special procedures for ensuring
    that no others use the bench while you are doing this work.
    Please send us this information.



    J. Jason Lin wrote:

        Hi SpecMat Committee,

        I would like to use hydrobromic acid 48% (MSDS sheet is
        attached) at the wbgeneral wetbench.

        My plan is to dip my wafers in HBr acid for a few minutes at
        room temperature, then transfer them to the savannah ald.  I
        would be using my own labware.  Also, my wafers/pieces will only
        have Si, Ge, and SiO2 (no metals to react with the acid).

        Please let me know if you require more information to make a
        decision on my specmat request.

        CORAL ID: jasonlin

    Mary X. Tang, Ph.D.
    Stanford Nanofabrication Facility
    CIS Room 136, Mail Code 4070
    Stanford, CA  94305
    mtang at stanford.edu <mailto:mtang at stanford.edu>

Mary X. Tang, Ph.D.
Stanford Nanofabrication Facility
CIS Room 136, Mail Code 4070
Stanford, CA  94305
mtang at stanford.edu

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