<s>
Thermal	B-Algorithm
scanning	I-Algorithm
probe	I-Algorithm
lithography	I-Algorithm
(	O
t-SPL	O
)	O
is	O
a	O
form	O
of	O
scanning	O
probe	O
lithography	O
(	O
SPL	O
)	O
whereby	O
material	O
is	O
structured	O
on	O
the	O
nanoscale	O
using	O
scanning	O
probes	O
,	O
primarily	O
through	O
the	O
application	O
of	O
thermal	O
energy	O
.	O
</s>
<s>
Related	O
fields	O
are	O
thermo-mechanical	O
SPL	O
(	O
see	O
also	O
Millipede	B-General_Concept
memory	I-General_Concept
)	O
,	O
thermochemical	O
SPL	O
(	O
or	O
thermochemical	O
nanolithography	B-Algorithm
)	O
where	O
the	O
goal	O
is	O
to	O
influence	O
the	O
local	O
chemistry	O
,	O
and	O
thermal	O
dip-pen	O
lithography	O
as	O
an	O
additive	O
technique	O
.	O
</s>
<s>
In	O
1992	O
,	O
they	O
used	O
microsecond	O
laser	O
pulses	O
to	O
heat	O
AFM	O
tips	O
to	O
write	O
indents	O
as	O
small	O
as	O
150nm	O
into	O
the	O
polymer	B-Language
PMMA	O
at	O
rates	O
of	O
100kHz	O
.	O
</s>
<s>
This	O
thermo-mechanical	O
data	B-General_Concept
storage	I-General_Concept
concept	O
formed	O
the	O
basis	O
of	O
the	O
Millipede	B-General_Concept
project	I-General_Concept
which	O
was	O
initialized	O
by	O
Peter	O
Vettiger	O
and	O
Gerd	O
Binnig	O
at	O
the	O
IBM	O
Research	O
laboratories	O
Zurich	O
in	O
1995	O
.	O
</s>
<s>
It	O
was	O
an	O
example	O
of	O
a	O
memory	O
storage	O
device	O
with	O
a	O
large	O
array	O
of	O
parallel	O
probes	O
,	O
which	O
was	O
however	O
never	O
commercialized	O
due	O
to	O
growing	O
competition	O
from	O
non-volatile	B-General_Concept
memory	I-General_Concept
such	O
as	O
flash	B-Device
memory	I-Device
.	O
</s>
<s>
The	O
storage	B-General_Concept
medium	I-General_Concept
of	O
the	O
Millipede	B-General_Concept
memory	I-General_Concept
consisted	O
of	O
polymers	B-Language
with	O
shape	O
memory	O
functionality	O
,	O
like	O
e.g.	O
</s>
<s>
However	O
,	O
evaporation	O
instead	O
of	O
plastic	O
deformation	O
was	O
necessary	O
for	O
nanolithography	B-Algorithm
applications	O
to	O
be	O
able	O
to	O
create	O
any	O
pattern	O
in	O
the	O
resist	O
.	O
</s>
<s>
Such	O
local	O
evaporation	O
of	O
resist	O
induced	O
by	O
a	O
heated	O
tip	O
could	O
be	O
achieved	O
for	O
several	O
materials	O
like	O
pentaerythritol	O
tetranitrate	O
,	O
cross-linked	O
polycarbonates	O
,	O
and	O
Diels-Alder	O
polymers	B-Language
.	O
</s>
<s>
Significant	O
progress	O
in	O
the	O
choice	O
of	O
resist	O
material	O
was	O
made	O
in	O
2010	O
at	O
IBM	O
Research	O
in	O
Zurich	O
,	O
leading	O
to	O
high	O
resolution	O
and	O
precise	O
3D-relief	O
patterning	O
with	O
the	O
use	O
of	O
the	O
self-amplified	O
depolymerization	O
polymer	B-Language
polyphthalaldehyde	O
(	O
PPA	O
)	O
and	O
molecular	O
glasses	O
as	O
resist	O
,	O
where	O
the	O
polymer	B-Language
decomposes	O
into	O
volatile	O
monomers	O
upon	O
heating	O
with	O
the	O
tip	O
without	O
the	O
application	O
of	O
mechanical	O
force	O
and	O
without	O
pile-up	O
or	O
residues	O
of	O
the	O
resist	O
.	O
</s>
<s>
The	O
thermal	O
cantilevers	O
are	O
fabricated	O
from	O
silicon	B-Architecture
wafers	I-Architecture
using	O
bulk	O
–	O
and	O
surface	O
micro-machining	O
processes	O
.	O
</s>
<s>
The	O
resistive	O
heating	O
is	O
carried	O
out	O
by	O
integrated	O
micro-heaters	O
in	O
the	O
cantilever	O
legs	O
which	O
are	O
created	O
by	O
different	O
levels	O
of	O
doping	B-Algorithm
.	O
</s>
<s>
The	O
integrated	O
heaters	O
enable	O
in-situ	O
metrology	O
of	O
the	O
written	O
patterns	O
,	O
allowing	O
feedback	O
control	O
,	O
field	O
stitching	B-Algorithm
without	O
the	O
use	O
of	O
alignment	O
markers	O
and	O
using	O
pre-patterned	O
structures	O
as	O
reference	O
for	O
sub-5nm	O
overlay	B-Algorithm
.	O
</s>
<s>
Pattern	O
transfer	O
for	O
semiconductor	B-Architecture
device	I-Architecture
fabrication	I-Architecture
including	O
reactive	B-Algorithm
ion	I-Algorithm
etching	I-Algorithm
and	O
metal	O
lift-off	B-Algorithm
has	O
been	O
demonstrated	O
with	O
sub-20nm	O
resolution	O
.	O
</s>
<s>
Due	O
to	O
the	O
ablative	B-Algorithm
nature	O
of	O
the	O
patterning	O
process	O
,	O
no	O
development	O
step	O
(	O
as	O
in	O
:	O
selective	O
removal	O
of	O
either	O
the	O
exposed	O
or	O
non-exposed	O
regions	O
of	O
the	O
resist	O
as	O
for	O
e-beam	B-Architecture
and	O
optical	B-Algorithm
lithography	I-Algorithm
)	O
is	O
needed	O
,	O
neither	O
are	O
optical	B-Algorithm
proximity	I-Algorithm
corrections	I-Algorithm
.	O
</s>
<s>
Maximum	O
linear	O
writing	O
speeds	O
of	O
up	O
to	O
20mm/s	O
have	O
been	O
shown	O
with	O
throughputs	O
in	O
the	O
104	O
–	O
105	O
μm2	O
h−1	O
range	O
which	O
is	O
comparable	O
to	O
single-column	O
,	O
Gaussian-shaped	O
e-beam	B-Architecture
using	O
HSQ	O
as	O
resist	O
.	O
</s>
