Diapositiva 1

1
Stamps Fabrication
Imprinting
Applications Nanoencoder
A) Silicon stamps The work developed under this
section has been focused on etching different
structures with ICP and RIE tools. Some different
processes were run with complete freedom in the
choice of masking materials, process parameters,
etching depths.
Standard demolding (static demolding) Fast
demolding (dynamic demolding) Advanced demolding
(A combination of them)
Optical encoders have been used for decades as
displacement measuring devices. An encoder
consists of a scale and a scanning device that
reads off the scale. Optical encoders consist of
grating or grid plates, and a read head which
senses displacement relative to the grating
scale. Highest resolution as a small fraction of
the grating period is achieved with a variety of
diffraction based schemes and improved
electronic.
Structures on the microscale and with different
aspect-ratios Different patterned surfaces on
the stamp (from 45 to 100 of the 4silicon
wafers) Different aspect-ratio on the nanoscale
(up to 125 nm and up to a.r4) Different
substrates used (PMMA75K and mr-I7030)
NIL may offer the technology needed to produce
encoders with very high resolution and/or
accuracy
1) SF6 O2 32-8sccm, P80mtorr, RFpower0.11
W/cm2, etch-rate7nm/s. DC bias15V. He
cooling.Selectivity to mask (resist) up to 101.
Positive profile around 10 of the total depth
observed.
Design
Silicon stamp manufactured by LETI
Static Demolding applied in two steps -During
the first step the pressure plate is sealed off
the substrate. Pressure air is let in through
port 1. It builds up a pressure in the volume 3
and causes the pressure plate 2 to act like a
pneumatic cylinder, that is, the plate moves
down, and seals off the substrate. -During the
second step demolding force is applied. Tool 5 ,
pressure plate 2 and substrate form a volume,
which is filled with pressurized air via port 4.
When tool and substrate move apart at low speed,
the pressurized air acts as demolding pressure at
the marginal areas of the substrate. As tool and
substrate move further apart, the pressurized air
is applied to a continuously increasing area of
the substrate until the substrate is completely
demolded.
SF6/O2 before releasing the photoresist
SF6/O2 etching. Depth200 nm.
SF6/O2 etching. Depth700 nm.
2) SF6-C4F8. 20-30 sccm. 15 mTorr. ICP 220W.
RFpower0.044 W/cm2. DC bias16V. He-cooling.
Selectivity to mask (resist) 5-71. Very
anisotropic process.
Stamps manufactured on silicon by ASM PAS
5000/300 optical stepper. Duty 320180 nm.
Depth200 nm.
Scheme of demolding. (1) Port for sealing
pressure, (2) Pressure plate, (3) Volume of
pneumatic cylinder for sealing pressure, (4) Port
for demolding pressure, (5) Tool, (6) Substrate.
Imprinting
Imprinted on 300 nm thickness of
mr-I7030. hrh0-hpr??200 nm
Microscale patterning with gratings among 1.6 ?m
and 5.5 ?m and a surface patterned of 45 over
4 silicon wafers
SF6/C4F8 before releasing the photoresist
SF6/C4F8 etching. Depth200 nm
Pattern transfer on silicon
SF6/C4F8 etching. Depth500 nm.
Pattern transfer on silicon by SF6/C4F8 ICP
process after residual layer etching by O2 RIE.
Duty is far from 11 due to O2 plasma
3) SF6-C4F8 (Bosch process) 150 sccm-100 sccm. 15
mTorr. ICP300w, RFpower0.055 W/cm2 (etch),
0.011 W/cm2 (dep). DCbias10V(etch),
DCbias3V(dep). He-cooling20ºC. Etch rate2
?m/min. Selectivity to mask up to 401.
Aspect-ratios up to 20.
These stamps were used to imprint 6 silicon
wafers coated by 300 nm of mr-I7030 and 500 nm of
PMMA75K. -The automatic demolding with speed of
1 mm/sec and speed controlled during 1mm works
right for both wafers and after opening the
chamber the substrate is kept at the bottom of
the plates and the stamp at the top. - We did not
use any mechanical or vacuum tool to fix the
substrate. -The aspect-ratio solved are between
0.03 and 0.12 for mr-I7030 (300 nm thickness) and
0.08 and 0.26 for PMMA75K (500 nm thickness). The
patterned area is around 45 of the whole 4
silicon wafer.
Pattern transfer on silicon as we use 210 nm
thickness of mr-I7030. Duty 350150 nm.
Static and Dynamic Demolding on the nanoscale
Dynamic Demolding Upon this instruction after
the embossing step and cool down the system, the
instruction open chamber fast is used so as to
lead to a fast separation between tool and
substrate. In this way, the adhesion force
between PDMS (compliance layer used) and
substrate acts like a uniform demolding force
without stress to the tool. Automated demolding
is only possible, if adhesion between the
backside of both substrate and PDMS is higher
than that between the stamp and substrate. This
operation is called dynamic demolding. This way
of operation requires reduce the force to close
to half value before demolding so as to make it
works properly.
Lift-off on glass
-Study of automatic demolding strategies when
nanofeatures are involved. -A design was agreed
with VTT to manufacture high aspect-ratio
structures on silicon and with resolution up to
125 nm. -Silicon stamps manufactured by VTT.
Bosch process. Depth up to 500 ?m
Monolayer NIL. It was impossible to release the
thermoplastic if not an oxygen etching was used
which also reduced the chromium thickness
B) Electroplating of silicon stamps The silicon
stamps manufactured from the NaPa mask were
replicated to nickel by electroplating. A thin
film of chromium and cooper was coated by
sputtering on it using this last one as seed
layer. They were electroplated in a nickel
sulfamate (Ni(SO3NH2)2-2H2O) bath with a
concentration of 300 gr/l and 30 gr/l of Boric
Acid so as to keep the pH constant (pH4). The
temperature of the bath was 50ºC and two steps
were used to improve the uniformity and reduce
the stress during the growing of the stamp
(Step10.19 mA/mm, Step20.65 mA/mm2). The
backside of the nickel plate is being polished
using a Nanoform polishing tool and these all are
being characterised in order to tune the
thickness and the uniformity of the stamp.
Bilayer NIL. LOL1000 (60 nm)mr-I7030 (300 nm).
Developer MF319. Hot NMP releasing agent.
It works right with NaPa stamps.
Lift-off with chromium on glass. Bilayer NIL
(LOL100060 nmmr-I7030210 nm). Duty 340160
nm Chromium thickness 40 nm. SEM image and AFM
topography.
Work to develop
Front side, Back side and details of growing
níckel stamps
Automatic demolding with nanofeatures. Maximum
A.R obtained with the different demolding
configurations. Correlation between static and
dynamic demolding and distortion or lack of
polymer on the imprinted samples. Advantages of
automatic demolding option. Strategies will be
discussed with PSI and new stayment or exchange
of samples will be proposed.
Silicon and glass nanostructured on a large are
21x19 millimeters, in which 7 large gratings are
defined. Silicon may work as a reflective phase
scale and glass as a transmission scale.