precursor: TiCl4
plasma gas: N2/ H2
temperature controlled vapour draw
dose control by fast pulse ALD valve
deposition temperature: 100° - 500° C
cycle time < 12 sec for 200 mm wafer
(shorter for smaller substrates, ca 9 sec)
0.33 A/ cycle (saturated dose)
1.65 A/ min, 10 nm/ hr (for 200 mm wafer)
(faster for smaller substrates)
uniformity: ± 0.5 %
resistivity < 175 µ ohm cm
(uniformity +/- 2 %)
even at 350° C
(vs 550° C for purely thermal ALD)
Cl content < 1 % |
ALD schematic
valve between remote ICP source
and chamber,
spectroscopic ellipsometry optional
Flex AL |
50 nm TiN grown on a 100 µm
deep trench etch with
aspect ratio of 300:1
bottom sidewall with 50 nm TiN
(roughness caused by the Bosch etch process)
EDS of TiN on the bottom Si trenches:
|
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 resistivity at low temperatures
from remote plasma reduction of TiCl4
compared to thermal ALD
substrate plasma preclean
plasma cleaning of the chamber
(SF6, typ 1 hour cleaning per month
of operation)
|
Saturation of TiCl4 showing
self limiting growth (200 mm wafer) |
Growth per cycle (GPC)
vs plasma time
Cl content and resistivity
vs plasma time = radical exposure time
Longer radical exposure times help
to get higher quality films !
|
