Plasma Technology  

The ALD film (orange) is used to shrink
the minimum feature size in
nanoimpring lithography.
(HSQ green)


with kind permission of
Molecular Foundry
at Lawrence Berkeley National Laboratory



Cross-sectional view by scanning electron
microscopy (SEM) of 40 nm pitch grating into HSQ film (top) and
after deposition of around 4 nm of alumina film (bottom). A 2–3 nm
gold film has been deposited to prevent from charging. The
trench height for both patterns is ~30nm.

ALD for Nanopatterning

metal precursor: TMA (tri methyl aluminium)
non metal precursor: O radicals and O2

temperature controlled vapour draw

dose control by fast pulse ALD valve

TMA + O2 plasma recommended for surface passivation
(rather than H2O thermal)

Deposition temperature range: 200°C recommended
for surface passivation

1.2 Å/cycle (saturated dose @ 200 °C)

Rate: 2 nm/min
Repeatability < ±1%

Carbon impurity < 2 at% @ 200 °C

Hydrogen impurity < 3 at% @ 200 °C

Post deposition anneal required at 425°C for
highest fixed negative charge density


C. Peroz, S. Dhuey, M. Cornet, M. Vogler, D. Olynick, S. Cabrini,
Nanotechnology, 23 (2012) 015305



Why remote plasma ALD ?

A "remote plasma" makes sure, the substrates
are NOT in contact with the plasma !

The remote plasma just cracks molecules,
so that very reactive species can be used
for the growth process.

Such reactive species often enable a very
efficient plasma preclean/ conditioning of the
substrates, lead to cleaner films and lower
the deposition temperature.

In Oxford systems it is possible to run
ALD processes using
- the thermal only method
- ozone assisted processes
- remote plasma assisted processes
together without any hardware change.
Multiple step processes using all technologies
can be chosen from the software.

low temperature ALD down to 25° C
is enabled by the use of O radicals;
this is not practical using thermal
H2O processes.




ALD schematic
valve between remote ICP source
and chamber,
spectroscopic ellipsometry optional







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