I don't think you can get a uniform coating. The trench will get at least
partially filled in, if you are spinning on a thin layer of resist. If you
are spinning on a thick layer of resist it will get completely filled in.

Robert

-----Original Message-----
From: mems-talk-bounces@memsnet.org [mailto:mems-talk-bounces@memsnet.org]
On Behalf Of Kamesh
Sent: Monday, January 30, 2006 11:09 AM
To: mems-talk@memsnet.org
Subject: [mems-talk] Photoresist Step coverage and conformality

Dear All,

I am a brand new member of Mems Exchange. It is really very nice to
have such a community to seek microprocessing advise.

My question :

1. I have a trench that it 3 microns deep and 30 microns wide. Can a
uniform coating of this trench be obtained by spin coating standard
photoresist ? What is the highest aspect ratio feature that can be
uniformly coated with standard photoresist ?

2. Is it possible to reliably fill an isolation trench that is 3
microns deep and 30 microns wide with CVD grown SiO2 ?

Thank you very much for the help !