Plasma Technology  

Temperature dependence of the growth per supercycle


Sr-rich layers ([Sr]/([Sr]+[Ti] = 0.6) show a
finer crystalline structure due to a higher nucleation
probability at the onset of the crystallization process

BF TEM images of STO films on Si3N4
windows with [Sr]/([Sr]+[Ti]) = 0.54 (top)
and [Sr]/([Sr]+[Ti]) = 0.60 (bottom)
after RTA at 550 °C RTA
Courtesy of TU Eindhoven

SrTiO3 (STO) ALD (radical assisted by remote plasma)


metal precursors:
Ti-Star, (pentamethylcyclopentadienyl)trimethoxy-titanium, CpMe5 Ti(OMe)
Hyper-Sr, bis(tri-isopropylcyclopentadienyl)strontium
with 1,2-dimethoxyethane adduct Sr(iPr3Cp)2 DME
non metal precursor: O radicals

controlled via bubbling

dose control by fast pulse ALD valve

deposition temperature: 150° - 350° C

The performance of Pt/STO/Pt capacitors could be varied between
high-k applications (CET ~ 0.7 nm) and integrated capacitor applications
(low quadratic voltage coefficient of capacitance alfa à 0 ppm V-2) by
choosing tailored compositions and microstructures of the plasma-assisted
ALD STO films.








Crystal structure of SrTiO
Red: oxygen, blue: titanium,
green: strontium

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.

low temperature ALD down to 25° C
is enabled by the use of O radicals;
this is not practical using thermal
H2O processes.




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







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