> In bulk microfabrication, I tried to fill a deep channel,
> which is around
> 200um. When I use AZ5214, there are lots of air bubbles
> coming out when I
> bake it. So how can I solve this problem?
> Do I need to use different PR? High thick PR?
> I want to try SU-8, but my friends told me that is a dirty
> material and
> not easy to remove after baking.

Try spraying acetone on the wafer before spinning.
While the wafer is still wet, dispense the resist and spin.
The acetone aid in wetting, and may work for you
depending on your exact geometry
        --Kirt Williams Agilent Technologies