Hi Chad,

Thank you very much for the suggestions.  I kind of tried the first one, but
still observed rippled around the posts.  I will try a really thick resist
to see if it helps.

As far as I know, we don't have a resist spray system, but I will check with
the people in the lab to make sure.

Thanks for the article as well.

erkin

----- Original Message -----
From: "Brubaker Chad" 
Sent: Thursday, September 08, 2005 1:50 PM
Subject: RE: [mems-talk] Surface Planarization

Erkin,

The problem here is that, especially with spin coating, the topography of
the posts will cause eddies to occur in the resist film leading to
non-planarity.

There are a couple of approaches to look into:

1) Try aiming for a thicker layer.  However, this can be difficult, since
with spin coating, the resist film will tend to need to be much thicker than
the topography (probably >5 µm).

2) Spray coating: if you have this capability available to you, you would be
able to place down a 2-3µm layer of material that should maintain a good
degree of planarization during the soft bake.  We've had some pretty good
results with planarization of some pretty extreme topography.

I know I've listed this link before, but to keep it easy, take a look at the
following link to Micro Magazine:

http://www.micromagazine.com/archive/04/03/brubaker.html

Specifically, you'll want to look at figure 8b.

Best Regards,
Chad Brubaker