This sound like under-exposed SU8. With a broad band source and no i-line
filter, I have found that it needs a higher dose than the prescribed amount.
Try increasing the exposure time, and I'm sure that would solve your
sidewall problems.



On Tue, Apr 22, 2008 at 2:21 AM, 郑瑞麟(Ruilin Zheng) 
wrote:

> Hello, everyone,
>
> I am doing some fabrication work with SU-8 2150 ultrathick layer, up to
> 400
> microns at a single layer spin coating.
> Because I just start my work, so there are a lot of problem stay in my
> way.
> After scanning the sidewall with laser scanning microscopy, I found that
> the
> side wall profile is partially vertical. At the part near the substrate up
> to about 1/3 of its height, the profile is concave.
>
> >From 1/3 to total height (up to surface ), the profile is fairly
> vertical.
> The difference between the concave part and the vertical part is about 40
> microns.  The UV source I am using doesn't have a filter for UV-light, so
> it is not a very coherent source.
>
> Does any one meet this problem before? Please give me some advice.