metal precursor: TMA (tri methyl aluminium)
non metal precursor: O radicals and O2
temperature controlled vapour draw
dose control by fast pulse ALD valve
deposition temperature: 25° - 400° C
cycle time < 4 sec (for 200 mm wafer)
(shorter for smaller substrates, ca 3 sec)
1.2 A/ cycle (saturated dose at 200° C)
18 A/ min, > 100 nm/ hr (for 200 mm wafer)
(faster for smaller substrates)
uniformity: < ± 0.5 - 2 %
(depending on substrate size)
repeatability < ± 1 %
C < 2% , H < 2.5% (at 200 °C)
Al2Ox, x = 3.05 by RBS and ERD
C, H, O impurities at 25°C are < 2%
refractive index 1.63
breakthrough voltage > 8 MV/ cm
dielectric constant > 8.5
growth rate vs TMA dose time at 200° C
growth rate vs plasma time:
A decreasing growth rate with decreasing
plasma time indicates incomplete surface
activation (removal of CH3 groups).
AFM RMS analysis shows very smooth films:
c-Si substrate: 0.0555 nm
20 nm Al2O3: 0.0589 nm
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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 of the substrates,
lead to cleaner films and lower the
deposition temperature.
low temperature ALD down to 25° C
is enabled by the use of O radicals;
this is not practical using thermal
H2O processes.
"Flex AL" for
Atomic Layer Deposition based on the
Plasmalab System 100
ALD schematic
valve between remote ICP source
and chamber,
spectroscopic ellipsometry optional
At a given temperature radical assisted
ALD gives higher film desities than
purely thermal ALD.
radical assisted Al2O3 ALD at 20° C
very low water vapour tansmission rate
"OpAL" for
Atomic Layer Deposition based on the
Plasmalab 80 Plus
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