I had luck using the following recipe on glass wafers.

1. cleaning : 5:1 Piranha / 10 min --> blow dry --> hot plate 145~150C /
10min
2. HMDS 3-4min
3. PR coating /AZ5214 / 4000rpm/ 30sec --> soft baking (100C, 1min)
4. Karl suss exposure / 18 sec (As you want) (9 mW/cm^2)
5. Hotplate 100C, 45 sec
6. Flood exposure, 180 sec (9 mW/cm^2)
7. Develop, AZ400K 1:5, short time --> hot plate 90C/ 20 sec
8. Hard Bake.

I think with your process, you may want to try using a lower concentration
of developer. When I used this one, I had to develop by time and
microscope inspection. The typical "mist" from resist coming off wasn't
visible while developing.

Just a guess.

Jesse Fowler

>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?