Let me suggest some factors that might have negatively impacted you.

1. The N2 gun may not have a filter inline or for some other reason not
be as clean as the N2 for your Spin-Rinse-Dryer.

2. The Spin-Rinse-Dryers primarily throws the water off through
centrifugal force rather than drying wafers.

Anyone who has statically dried wafers knows that your Dionized Water is
full of non-ionic contaminants such as dissolved silica and organics,
usually bacterial cell walls and such. In blowing it off with an N2 gun
you can dry the water and leave the residues, where as a
Spin-Rinse-Dryer spins the wafer off and not dry it off.

I have had a difference in impact whether I did spin dry with and
without heat on some substrates.

For your particular case, I speculatively suggest the following.

1. IPA dryer is a good option if you have one. It is very clean and the
water is removed by condensation of IPA into the wafer and the
condensate IPA flushing the surface clean.

2. You might rinse the water off with IPA and then blow dry with the N2.
However, the IPA would need to be very pure, or it would leave its own
residues around the edges.

3. Distilled water, kept in a polyethylene bottle. Glass has some slight
solubility in water. It might not leave the residues.

4. Have a reverse osmosis filter for your Dionized Water. Don't be
surprised it it clogs up fairly soon.

Ed

-----Original Message-----
From: mems-talk-bounces@memsnet.org
[mailto:mems-talk-bounces@memsnet.org] On Behalf Of Xiaochen Sun
Sent: Tuesday, February 05, 2008 10:25 AM
To: mems-talk@memsnet.org
Subject: [mems-talk] Si/Ge pieces surface cleaning

Hi,

I used to grow materials using UHVCVD on Si wafer. To prepare the wafer,
we usually did RCA cleaning followed by N2 spin dry. And the growth was
successful. Recently, we want to try some growth on Si/Ge pieces, but
have this surface preparation problem. The spin dry machine can only
accept 4" or 6" wafer but not pieces. We tried to use N2 gun to blow the
pieces after chemical treatment. But the result was not so good,
especially on the peripheral part of the pieces due to the possible
water residue on the edge.
Do you guys have any experience on pieces sample growth and give some
advices?