Hi Ning,

That hadn't occurred to me; thanks for the insight. If this was the driving
mechanism, wouldn't I expect higher reflectance from the gold areas than
from the areas where the alumina surface was bare (alumina is dull white
whereas the gold is shiny)?  The resist seems to be preferentially exposed
where it is adjacent to the bare alumina; the other areas (adjacent to gold)
develop out normally, indicating relatively less exposure.

Regards,
Rob

-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of ning
xue
Sent: Wednesday, February 02, 2011 5:06 PM
To: General MEMS discussion
Subject: Re: [mems-talk] patterning SU8 on alumina

Hi Rob

That is because the rough surface of Au and Al, so there is UV reflection to
the via hole. Then the via hole is exposed.

Thanks
Ning