Hi,

Your pre-oxide clean is incorrect, use Sulfuric/H2O2 at 130c for 20
minutes, get the sulfuric to 130c then add 100ml of H2O2 slowly.
followed by SC1, SC2 and 50:1 HF dip, that will give you a clean
surface.

If the wafers are new out of the box you can skip the clean, nothing is
better than clean wafers right out of the box.

Rick


Rick Morrison
Senior Member Technical  Staff
Group Leader Microfabrication Operations
Draper Laboratory
555 Technology Square
Cambridge, MA  02139

W  617-258-3420
C   508-930-3461



-----Original Message-----
From: mems-talk-bounces+rmorrison=draper.com@memsnet.org
[mailto:mems-talk-bounces+rmorrison=draper.com@memsnet.org] On Behalf Of
H V Balachandra Achar
Sent: Sunday, January 22, 2012 3:03 AM
To: mems-talk@memsnet.org
Subject: [mems-talk] Pin holes in thermal oxide

Dear All,

I am using 1 micron thick thermal oxide, grown using dry-wet-dry
sequence, as
the mask during bulk etching of silicon using KOH solution. After
oxidation I
notice pin holes in oxide surface. Because of these pin holes, silicon
is
getting etched in KOH at places where I don't want to etch.

Please suggest a remedy.

Note: I am using (100) p-type 1-10 ohm-cm Si wafer.
Cleaning sequence: TCE, acetone, nitric acid, dilute HF
Dry-wet-dry durations: 20 min - 4 hrs - 20 min, followed by 30 min
annealing
in N2 ambient.

Thank you

--
H V Balachandra Achar