Hi Abishek,
                     I have done two coats of AZ4620. Use HMDS before the
first coat only. Spin the resist at the desired RPM and bake for 90 secs at
110 deg. Let it to cool and spin the second coat and bake for 2 mins and the
subsequent coat for about 4 to 5 mins. Prolonged bakes causes the resist to
harden quite a bit and may need extended exposure and develop times. A 20 um
thick layer took me about 2 min 30 secs to develop in AZ 400K (1:3)

Saravana P. Natarajan
Grad. Research Assistant - RF Microsystems Group
University of South Florida,Tampa, FL,
Ph: 813-974-4851
Fax: 813-974-5250

------------------------------

Message: 5
Date: Wed, 27 Sep 2006 22:20:11 -0700
From: "Abhishek Jain" 
Subject: [mems-talk] photoresist multiple coating
To: "General MEMS discussion" 
Message-ID:
        <[email protected]>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed

Hi
I want to do multiple coatings(2-3) of resist AZ4620 or a similar
positive resist (not SU-8) to get thicknesses of 50-75um. I am looking
for a recipe to do this. Please advice if you have any experience.