Plasma Technology  

NbN deposition rate and uniformity (6" wafer)
vs TBTMEN dosing time
measured by spectroscopic ellipsometry
From this graph it was decided to use 5 s as the standard dosing time.

specific resistance and deposition rate vs plasma time
From this graph it was decided to use 30 s as the standard plasma time.
Longer plasma times do not change the rate, but give better quality films.
(Plasma times of 10 s have also been used.)

specific resistance and deposition rate vs process pressure
Low pressures give low resistance !

thickness and sheet resistance uniformity (6"wafer)
NbN PE ALD at 8.5 mTorr, 450 cycles

NbN PE ALD for gate electrodes

specific resistance and deposition rate
vs deposition temperature
The rate is not dependent on the temperature
indicating, that at 350° C CVD is still not present.


specific resistance, film composition and rate vs N2/H2 ratio
(The film composition was measured by XPS.)
At 2% N2 NbN is grown, while a H2 only plasma give NbN0.8.


PEALD were also compared to MOCVD NbN electrodes.
Films grown by PEALD provide a better interface quality (low defect
density and interface roughness), and a considerably lower
deposition temperature can be used.

Why remote plasma ALD ?

A "remote plasma" makes sure, that the
substrates are NOT in contact with the plasma !
Light ion bombardment can be achieved by
lowerign the process pressure using the turbo pump.

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.

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

Metal precursor: TBTMEN
Delivery Method: bubbled with argon
Non-metal precursor: H2 (and N2) plasma

- 0.65 Å/cycle
- 20 - 60 sec cycle time
- Deposition rate ~ 0.2 - 0.6 nm /min
                             ~ 12 -  36nm /h

with kind permission of Dr Bauer, Dr Hinz
Fraunhofer IISB Erlangen


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