Plasma Technology  

SEM TiN ALD conformal coating

Conformal TiN coating
of deep trench with increasing
aspect ratio
40 nm very uniform coating
from top to bottom

self limiting process steps:

step 1: TiCl4
step 2: N2 + H2 (plasma ALD)
purge -> step 1

Tem picture TiN ALD

TEM picture: 110 A TiN by plasma ALD

TiN ALD (radical assisted by remote plasma)

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.

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)

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.





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 !

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