Hi Yawei,
     I've been doing 5214 at a much thinner thickness (1.25 um) but I can
tell you some about what I've done.  If you really need that thick a film
(what thickness are you trying ot liftoff?), you might want a different
resist like a negative resist, a bi-layer, or a different 5200 series.
    My process looks a lot like yours except I spin HMDS on the wafer before
the resist to promote adhesion.  Just 8-10 drops on a 4" wafer and then spin
at 2500 RPM for 30s.  My PEB is for 2 min @ 120C on a vacuum hotplate.  I do
my flood exposure (no mask) at ~2.5x the time of the initial masked
exposure.  Finally, I develop in 3:1 AZ 400K developer.  Hope this helps.

-Lou


>From: "Yawei Li" 
>Reply-To: General MEMS discussion 
>To: 
>Subject: [mems-talk] help needed for image reversal photoresist AZ5214
>withabout 3um thickness
>Date: Fri, 24 Mar 2006 13:05:55 -0500
>
>Hello everyone,
>
>I am working on the image reversal photoresist AZ 5214 (about 3um
>thick)on 4" Si wafer with undercut profile for metal liftoff.
>
>The recipes I tried are as follows:
>
>HMDS
>Spin @ 1000 rpm for 45 sec
>prebake 95 degree 60 sec on hotplate
>Image exposure   5-40 sec at 8.8mW/cm^2
>PEB   115 degree for 1-2min on hotplate
>Flood exposure 27-120 sec at 8.8 mW/cm^2
>Development in AZ 400K (1:4)
>
>But I could not get the feature clear before the exposed area peel off
>even I increase the imagewise exposure dose and PEB.
>
>Does anyone have experience with AZ 5214 for 3um thickness?  Can you
>share your recipe with me or give me some suggestion about the recipe?