Post-grind and CMP clean

Jim McVittie mcvittie at snf.stanford.edu
Mon Jan 12 15:08:46 PST 2004


Mary,

My understanding is that if there are any particles on the wafers, they
have to go through the cleaning procedure put together by Theresa Kramer
back in 1998. If there are no particles, they must go the post KOH
clean.    Jim

Mary Tang wrote:

> Hi all --
>
> There are at least two groups that seem to do CMP or wafer grinding
> outside and then clean their wafers so that they can be processed in
> "clean" equipment in our lab.  I know many emails have gone back and
> forth as to possible concerns about particles, above and beyond the
> alkali and metal ion contamination...  but was there ever a final
> decision on procedures?  We're getting a couple more requests now (such
> as Tariq's from earlier this week.)  What do you all think?
>
> Mary
>
> --
> Mary X. Tang, Ph.D.
> National Nanofabrication Users' Network
> Stanford Nanofabrication Facility
> CIS Room 136, Mail Code 4070
> Stanford, CA  94305
> (650)723-9980
> mtang at stanford.edu
> http://snf.stanford.edu
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CMP Cleanup Procedure
Theresa Kramer
April 1998

Starting wafers: 4" silicon with thermal oxide and LTO, nonmetal

CMP: Rodel pad Q1400 (used for ICs), Rodel slurry ILD1200 (KOH based,
silica particle abrasive) at San Jose State

Clean:
        SC1 clean * H2O:H2O2:NH4OH 5:1:1 10 min, running DI 5 min at
wbgeneral in clean, nonmetal glassware (better to have this done at San
Jose State before the wafers dry, but if you cannot, possibly transport
wafers still wet back to Stanford).  This step leaves slurry residue and
silica particles.  If they are dry, they are much more difficult to
remove.

        Inspect wafers under dark field to see the particulates for later
comparison if they were allowed to dry.  
       Scrub wafer front and back with polyvinyl alcohol (PVA) sponge in
2mm sheet form in clean glassware at wbgeneral. PVA sponge available from
Rippey.  I put one sheet at bottom of large beaker filled with DI, then
the wafer, then used a second sheet folded to scrub the surface of the
wafer for several minutes.  The bottom sheet is to avoid scratching.  The
wafer should be flipped and scrubbed on both sides.  Follow with DI rinse.
Make sure to use clean gloves as they are in contact with the PVA sponge
in the DI in contact with the wafer.

        Inspect wafers under dark field to confirm particulates have been
removed.

        KOH cleanup (standard) * H2O:H2O2:HCl 5:1:1 20 minutes in clean,
nonmetal quartzware at wbgeneral, DI rinse 5 min.

Wafers may now return to mainline equipment.    
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