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exposure dose, post exposure bake temperature and time for
each set of feature size. Indeed Hong et al. reported in their
study of the significant fabrication parameters associated
with the de-lamination of 100µm thick SU-8 film from a
silicon wafer substrate and their effect using a neural
network model. The SU-8 layer had been blank-exposed by
photolithography and they showed that a higher exposure
dose lowers the temperature at which de-lamination starts to
occur, increasing de-lamination [19]. It is consistent with
our observation that the smaller feature sizes on the SU-8
stamp, that is 300 nm, which require a higher electron beam
exposure dose, are also the first ones to be delaminated.
With larger feature size obtained by photolithography, no
delamination was visible on COC films, but it occurs with
PMMA films.
IV. CONCLUSION AND PERSPECTIVE
The feasibility of using SU-8 epoxy stamps has been
demonstrated, as well as a high-speed fabrication process of
large area micronic and sub-micronic array of lines suitable
for small and medium mass production.
Micro-features of 100 µm width and 80 µm depth were
successfully replicated in 130µm thick Topas 8007 COC
foils in a two-pass process at a temperature of 110 and 145
°C for upper and lower roll respectively, using a pressure of
6 bars and a feed rate of 0.3 m/min. The replica was
produced in 125µm thick PMMA foils in six passes at a
temperature of 166 °C for both upper and lower rollers
while applying a pressure of 6 bars and a feed rate 0.1
m/min.
Sub-micronic features of 400 nm width and 570 nm depth
were produced in COC in three passes at a temperature of
133–137 °C for upper and lower rolls, using a pressure of 4
bars and a feed rate of 0.4 m/min, and in PMMA in four
passes using the same parameters for the embossing process
as those for embossing 100 µm wide features.
The SU-8 stamp fabrication process was performed in
less than a few hours using photolithography for tens to
hundreds micrometer features and electron beam
lithography for the sub-micronic range down to 300nm. It
also gives the possibility of hybrid manufacturing of both
micronic and submicronic features on the same stamp.
The high resolution capability of SU-8 combined with the
high production rate of roll embossing technique are highly
promising for a wide range of applications.
ACKNOWLEDGMENT
This work was performed within the framework of the
Carnot-Fraunhofer French-German project “3μP: Microfluidic
platform for multiple samples with multiple analytics
to run diagnostic analysis” and the French FUI CONPROMI
project.
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