CMP at Cornell

Jim McVittie mcvittie at snf.stanford.edu
Mon Nov 22 13:05:32 PST 2004


Bipin,

The following is the post CMP cleaning procedure we came up with many
years back for wafers coming back from San Jose State.   Jim
----------
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.
----------
Bipin Rajendran wrote:

> Hi,Regarding my earlier question regarding CMPing wafers at Cornell
> and bringing it back to our lab ( email below), I talked to Dr. Jim
> McVittie, and he suggested that I should do a normal RCA clean before
> using equipments in our lab.ThanksBipin
>
>      ----- Original Message -----
>      From: Bipin Rajendran
>      To: specmat at snf.stanford.edu
>      Sent: Thursday, November 11, 2004 9:27 AM
>      Subject: CMP at Cornell
>       Hi,I wanted to CMP an LTO layer on fully processed 410
>      wafers. I am planning to do it at Cornell Fab, and here is
>      what the In-Charge of CMP tool there has written to me about
>      their tool: In terms of the gold contamination, we do not
>      restrict gold from the tool and in the past people have
>      polished a gold layer on the tool trying to do some gold
>      damascene work.  The last time that was done was probably 6
>      or more months ago.  The main parts of the tool that contact
>      the gold are the CMP pad and the carrier head film, both of
>      which are frequently changed.  We have people using CMP who
>      are making transistors here and they have not expressed any
>      issues with gold contamination.I would be bonding another
>      wafer to this CMPed LTO. Can you please let me know if such
>      a bonded wafer pair can go back to SNF for normal
>      processing. (May be atleast semi-clean
>      instruments?)ThanksBipin
>
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