Plasma Technology  

with kind permission of Uni Jena
300 nm TiO2 grown on Si
by remote plasma ALD in an OpAL



By varying the deposition temperature it is
possible to change the crystallinity of the TiO2.

XRD spectrum showing the change from
amorphous to anatase from 200° to 300° C.
The broad peak is crystal silicon.

 




FlexAl

TiO2 ALD (radical assisted by remote plasma)


precursor: TTIP = Ti(OC3H7)4
Titanium isopropoxide



plasma gas: O2

deliver methode: bubbling

dose control by fast pulse ALD valve

deposition temperature: 25° - 300° C

cycle time < 10 sec for 200 mm wafer
(shorter for smaller substrates, ca 7 sec)

0.47 A/ cycle (saturated dose for amorphous films)
2.8 A/ min, 17 nm/ hr (for 200 mm wafer)
(faster for smaller substrates)

uniformity: ± 2 %

C and H content < detection limit (2 %)

refractive index 2.4

Ti:O = 1 : 2 by RBS

Mass Density 3.8 g/cm3

Band Gap 3.5 eV (at 200° C)

 

data courtesy of TU Eindhoven

deposition down to room temperature:
characteristic ALD linear growth rate from
0.4 - 0.55 A/ cycle,
measured by in situ ellipsometry

 

RBS analysis of 66 nm TiOx on Si/ SiO2
Ti:O = 1:1, no C, no H
Si has been partially masked
mass density 3.8 g/cm3
(vs 4.2 g/ cm3 for bulk TiO2)


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.

substrate plasma preclean
plasma cleaning of the chamber
(SF6, typ 1 hour cleaning per month
of operation)

 

OpAl


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

 

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