Online proceedings - EDA Publishing Association

Sub-micronic features with a final dimension of 400 nm
wide, 570 nm height and 50 µm long were produced in SU-
8 on silicon after exposure, development, PEB and hard
bake as shown in Fig.5. For the 400 nm feature array,
exposure dose of 4 µC/cm² was selected. However, with
larger feature size less exposure dose is required.
11-13
May 2011, Aix-en-Provence, France
m/min as shown in Fig.7. Reduction of feed rate in PMMA
case shows difference as it is inversely proportional to
holding time of applied pressure and allows polymer filling.
Also, its value directly affects the production rate. Good
pattern transfer is obtained by changing only the number of
passes compared with the micronic features replication.
Fig.5 SU-8/Si mould with submicronic features of 400 nm wide and 570
nm height. Inset: Magnification view of SU-8 feature cross-section 40KX
First set of trials for roll embossing with 400 nm wide
features was conducted in Topas 8007 COC. Embossed fine
features of 400 nm width and 570 nm depth were produced
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 as shown in Fig.6. However, an incomplete
filling problem at sharp edges appears (see inset of Fig.6).
Fig.7. PMMA replica embossed from SU-8/Si mould with submicronic
features of 400 nm wide and 570 nm deep. Inset: Magnification view of the
channel section Mag. 40KX
C. Mould defects after replication
The SU-8/Si mould has been used for roll embossing in
COC foils without facing any problem. However, after
using the SU-8/Si mould to emboss in PMMA, a complete
de-lamination at the 300 nm features and partial delamination
at the 400 nm features were observed on the
stamp as shown in Fig.8 and its inset.
Fig.6. Topas COC 8007 replica embossed from SU-8/Si mould with
submicronic-features of 400 nm wide and 570 nm deep. Inset:
Magnification view of the channel section Mag. 40KX
It was expected that by increasing the embossing
temperature and pressure, as well as decreasing feed rate,
this problem could be resolved. But comparing these results
with another COC embossed replica produced in three
passes at the higher temperature of 166 °C for both rollers
and a higher pressure of 6 bars and a feed rate of 0.3 m/min,
shows no big difference at the sharp edges.
Submicronic features replicated in PMMA in four passes
at a temperature of 166 °C for both upper and lower rollers
while applying a pressure of 6 bars and a feed rate of 0.1
Fig.8. SU-8/Si mould with submicron features of 400 nm wide and 570 nm
height after embossing. Inset: Magnification view of feature cross-section
Mag. 40KX
This de-lamination could be explained by the relatively
high adhesive forces between the master patterns in SU-8
and the PMMA foil to be embossed. These adhesive forces
could be reduced if an anti-sticking layer is deposited before
starting the embossing process. This anti-sticking layer
could be a deposited layer of Teflon-like octo-fluoro-butane
(C 4 F 8 ) gas.
Also, the adherence between patterned SU-8 resist and
the silicon wafer could be increased by optimizing the
282