Hi Julie,

You can do a sector exposure using a round disk with a cut-out pie shape to
expose your PR with different doses on the same substrate. You then can check
under the microscope which one looks best after development. I do not know the
exact light output of your tabletop aligner, but my bet is that ~5 seconds will
do just fine. S1813 is a very forgiving resist.
To get vertical sidewalls in your resist, try a hard contact exposure in
combination with the right expo time. You can pretty much tell under the
microscope whether they're vertical or not.
Regarding selectivity, there is bound to be a bunch of papers etc. you will be
able to find online, try the STS website. It very much depends on the plasma
power, pressure, gas mixture etc. on what your selectivity is going to be. I
personally prefer oxide as a mask for the Bosch process, but PR will certainly
work.

Good luck

Jobert van Eisden
College of Nanoscale Science and Engineering
SUNY Albany


-----Original Message-----
From: mems-talk-bounces@memsnet.org
To: General MEMS discussion
Sent: 6/27/2005 4:43 PM
Subject: [mems-talk] exposure time for S1813 photoresist


Hello all,

I'm finally going to spin-coat 1 micron S1813 photoresist on my sample
to form a
mask for future DRIE etch of silicon (Bosch process).

My photomask (for test purpose) includes open regions of 2 microns wide
(to be
etched) separated from each other by 1 microns (for the shortest
dimensions). I
would like these patterns to be transferred the most accurately to the
photoresist (vertical wall).

I so need to optimize the exposure time. Does someone have an idea of
this time
(with and without Gline filter in Model 200 Tabletop Aligner)?

Another unknown is the S1813 selectivity in Bosch process (ASE STS
DRIE).



Thank you,


Julie.



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