>Dear MEMS community,
> Has any one used metal on SU-8 photoresist. We are having problems metal
sticking to SU-8.
>I would appreciate any inforamtion on it is passed on.
>Regards,
>Padmaja
>Padmaja Ramadas                                                (972)-927-1108
(w)
>Texas Instruments Incorporated                 (972)-995-7785(fax)
>P.O. Box 655012
[email protected]
>M/S 945
>Dallas, Texas  75265
>
>
>

Dear Sir,

It makes now 2 year and a half that I am working with SU8 photoepoxy (this
material has partily been developed in our lab at the Swiss Federal Insitute of
Technology in Lausanne) and one of the first device I have developed was a SU8
thermal flow sensor with integrated metal resistors, depositied on the
photoepoxy.

If the SU8 is polymerised, there should be no major problem of sticking.All the
metal depostions I have done so far have been done by evaporation, but I think
it should be the same thing can be done with a sputtering machine. I first use a
chromium layer of about 20 to 50 nm (not more!) in order to improve the
adhesion. Than I can deposite metals such as gold, copper, aluminium, etc with
thicknesses of more then 1 micron. These metal layers can also be patterned in a
standard photolithographic way (no lift-off technology).

If the SU8 is polymerized, then you can expect several problems, especially when
you want to pattern the metal with for example the help of a postive
photoresist. In fact when you put your wafer on a hot-plate or inside oven to
make the softbake of the photoresist, the non-polymerized SU8 will become soft
and deforms the metal layers.

I have notice that there is however one case in which the metal don't stick to
well  on the SU8. It happens when you have a non-polymerized SU8 layer covered
with a metal layer on which you have deposited a second SU8 layer.This last
layer is polymerized. Now when you develop and 'wash' away the nonpolymerized
SU8, the metal might not stick on the upper polymerized SU8 layer.  For this
case we are now trying to develop a modified version of the SU8 which is
supposed to have better sticking properities.

I hope this helps you. Should you have any more questions, please contact me. We
are now creating a new company where we want to commercialize SU8 photoepoxy
products and service. If you are interested, we would be pleased to collaborate
with you.

Best regards,

Dr Louis J. Guerin

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Dr Louis J. Guerin
Institute for Microsystems
EPFL- Swiss Federal Institute of Technology Lausanne
CH-1015 Lausanne
tél: (+41 21) 693 5857
fax: (+41 21) 693 6670
email: [email protected]

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