Questions about the ZEP-520A
James W. Conway
jwc at snf.stanford.edu
Tue Feb 16 09:29:42 PST 2010
Great questions which I will share with the Raith On Line Community...
ZEP-520A makes a great liftoff structure when exposed at below 10 kV.
It is very high contrast material and about three times faster than our
normal PMMA materials. It also has suitable etch resistance and
selectivity for RIE using the normal process gases with the exception of
In normal careful dose determination you should see a clearing dose
threshold of 37 to 40 µC/cm**2 at 10 keV for areas above 100 nm in
size. At the lower dose you may see some resist residues visible as
small fringes in the corners of the area test boxes. This is normal and
a slight increase in dose should clear these edges well. Always employ
the very slightest of agitation during development and be sure to not
over-develop your patterns.
In the past have employed very gentle descum processing in the past for
Ohmic contacts and and dots using very low powers applied with Oxygen --
but only for 5 - 15 second descum cycles at less than 50 W of power.
(My old etcher was a MARCH Mini-80 tabletop RIE system when I used 5O W
for 15 seconds at 0.200 T O2 pressure and after a complete pump down and
2 Ar purge cycle to remove water vapor and O2 from the chamber walls.)
The issue with descum processing of lift off structures is you may
simply sputter away some of your reentrant profile in the resist and
that will make it more difficult to lift off cleanly.
Please see me if you need any assistance in your inspections or to
develop your process parameters as I have lots of experience working
Other Users care to report their doses used or add you comments to this
thread? I am reiterating our process for a new process sheet to come
out in March.
Your comments are welcomed.
Donkoun Lee wrote:
> Hi all:
> I have some questions about the ZEP-520A. Now, I do my e-beam process with ZEP-520A. After exposure, I deposit metal layers and do lift-off process in order to make an electrical contact. However, I am wondering if there are residues(scum) after developing process with Xylenes and Iso-propanol or not.
> If there are residual layers (scum) after developing process, do I need to do oxygen plasma process (descum process) to remove the residues? If I need to do the O2 plasma process, can I share the recipe?
> Thank you.
> Kind Regards,
> Donkoun Lee
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