Hi,

Regan Nayve wrote:

>Hi
>
>There is an article published in IEEE MEMS 1998 Proceedings
>that deals with SU-8.
> "Taguchi Optimization for the processing Epon SU-8 resist"
> B.Eyre,J.Blosiu and D.Wiberg
> Center for Space Microelectronics Technology
> Jet Propulsion Laboratory
> California Institute of Technology
> Pasadena,CA 91109
>
>Optimized process variables such as softbake time,exposure time,
>post-exposure time,develop time and sustrate type for SU-8 with
>73% solvent was obtained.
>
>Hope this could be of help.
>
>Regan Nayve
>
>
>Zeng Yi wrote:
>>
>> Dear Members:
>>      I am new student in MEMS. Now I am concerning to use SU-8
>> photoresist for some microstructures. But I do not know how to
>> control the depth of the SU-8 layer? Could anyone tell me something
>> about that? Thank you for your time and consideration.
>> Zeng Yi
>>
>>
>

The paper:

"Taguchi Optimization for the processing Epon SU-8 resist",  B.Eyre,J.Blosiu and
D.Wiberg, IEEE MEMS 1998 Proceedings

has to be considered very carefully and with a lot of caution. In my opinion the
process parameters given in this paper are far away from the optimum parameters
needed to achieved good and useful structures of SU8. For example the exposure
times are much to long. Normally for a 100 micron thick layer, about 200 mJ/cm2
are needed. With a mecury lamp having an intensity of 10 mW/cm^2, 20 seconds are
enough and not 5 minutes as it is stated in the article. Furthermore this long
exposure time (5 minutes) is also the reason why there is a crust formation on
the top of the structures. In fact what happens when you illuminate to much, is
that you heat the surface of the SU8 (or if you want you the part of the SU8
that is in contact with the mask). This overheating gives rise to some strange
diffusion phenomenas of the photoinitiator at the interface between the SU8 and
the mask, thus polymerizing the non-exosed SU8 and creating these crusts.

Best regards

Dr Louis J. Guerin

****************************************************
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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