Hi,

the process looks fine. I never used a conductive layer on top (because I didn't
need it) but it is right the way your doing it (gold on top of PMMA). Actually
you could also put the gold below if you wanted to. The gold layer doesn't
absorb the electrons necessary to expose your resist. It's just to dissipate
e.g. the backscattered eelctrons away.
However, I think the 30 kV is quite low but that depends on the feature sizes.
The dose factor doesn't say anything (it should give something like µC/cm2).
Check the literature/internet for the clearing dosage (amount of energy
necessary to fully remove a large exposed PMMA area). Use that as starting point
for your experiments.
Otherwise, check if your gold strip agents does not affect the PMMA.

I'm using ZEP520 for my structures (50 nm pillars and holes in 100-200 nm
resist). The dose I'm using is around 240 µC/cm2 at 100 keV acceleration
voltage.

One other thing, some conversion programs for the ebeam writers are quite weird.
Be sure that your structures are actually converted right.

Havefun,
maria


________________________________

Von: mems-talk-bounces@memsnet.org im Auftrag von li shifeng
Gesendet: Mi 26.11.2008 17:49
An: mems-talk@memsnet.org
Betreff: [mems-talk] EBL on the glass (more details)

Hi, All

I posted a message about EBL on the glass substrate couple days ago. I got
several valuable replys. In order to get more help, I would like to talk a bit
of detail about my case.

I try to write patterns on the glass substrate. In order to get rid of surface
charge problem, I sputtered 5nm gold on the top of PMMA. I used 30KV ebeam to
expose the patterns. Meanwhile, I used multiple dosage to find the optimal
exposure parameters. The dose factors I used are 1, 1.5, 2.0, 2.5, 3.0. After
exposure, I have to strip gold layer to develop PMMA.  I put some large features
in the design so that I can easly identify the position of the patterns. But,
after development, I cannot find any patterns on the glass substrate. I may
believe this maybe due to underexposure because the layer of gold may absorb
some electrons during exposure.

I am looking for any experiences similar like my case or any working receipe to
share.