The cleaning is not good - use piranha clean followed  by BOE and VERY clean
water rinse. TCA & acetone, unless filtered, usually leave particulates on the
silicon that are not removed be Nitric.

-----Original Message-----
From: mems-talk-bounces+shay=mizur.com@memsnet.org
[mailto:mems-talk-bounces+shay=mizur.com@memsnet.org] On Behalf Of H V
Balachandra Achar
Sent: Sunday, January 22, 2012 10:03 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