Improved plasma
ALD of nitrides bysubstrates biasing
Subtitle of presentation
Shohei Ito
OI Japan Service Manager© Oxford Instruments 2022

1

Introducing FlexAL RF Substrate Biasing
FlexAL system equipped with substrate biasing enables extended processcapabilities
100

RF substrate biasing can be applied during thin film deposition
to increase the ion energy and influence film properties suchas refractive index, conductivity, stress, crystallinity, density, …

Voltage (V)-100

FlexAL®

-200

Vsub or Vbias

-300
-400

0V <Vsub> (Ground)-59V <Vsub> (5W Bias)-140V <Vsub> (20W Bias)-300V <Vsub> (80W Bias)

-500
-600

PlasmaVpSheath∆VVsub∆V = Vp – Vsub
Substrate

0204060

80100 120 140 160

Time (ns)Increasing bias

RemoteH2 / Ar
PlasmaPrecursor
Inlet

Vp0Increasing
thetableelectrode power results in an
increase of measured DC
bias voltage at table.

RF-Bias© Oxford Instruments 20222

Deposition of conductive nitrides TiN and TaN

Material

TiN

Precursor
TiCl4
Co-reactant
N2/H2 plasma
Deposition temperature
300°C - 550°C
Thickness per cycle~0.35 Å/cycle @ 350 °C
Thickness uniformity 200 mm< 3.5%< 150 µΩcm @ 350 °C< 100 µΩcm @ 550 °CResistivity• TiN deposition with low resistivity
using both halide precursors(TiCl4) and also metal-organic
precursor (TDMAT).

TiNTaNTDMAT
N2/H2 plasma
100°C - 350°C~0.5 Å/cycle @ 200°C< 3.5%< 300 µΩcm @ >200°C< 150 µΩcm (RF bias)

TBTDMT
H2 plasma
250 °C – 350 °C~0.4 Å/cycle @ 300 °C< 3.5%< 1000 µΩcm @350 °C< 300 µΩcm (RF bias)

General recipe for RFsubstrate biasing• TiN and TaN benefit from RF
substrate biasing by lower film
resistivity.

© Oxford Instruments 2022

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Biasing results TiNUsing biasing generally higher conductivity obtained for
conductive nitrides. Allows shorter plasma exposure
times and lower deposition temperatures.
• TiN results:• Using TDMAT for 200 °C deposition ahigh conductivity was obtained alreadyat short total plasma time (10s).
• 20W bias (~100-150 Vbias) for 5 s:
109 µΩcm for 33.2 nm thickness
General recipe© Oxford Instruments 2022

55

Effect of bias on plasma ALD TiN• ALD by TDMAT and 10 s H2/Ar plasma at 200 °C.

• Tuning of crystallinity, resistivity, density, andstress.

Faraz et al., ACS Appl. Mater. Interfaces 10, 13158 (2018)© Oxford Instruments 2022

66

Effect of bias on plasma ALD NbN
Resistivity and Film Stress (on Si substrate) vs Biasing Power for NbN Films
processed at 250 ℃• Resistivity and film stresscan be controlled by tuning
substrate biasing power• Coincidence and possible
correlation can be observed
between resistivity and filmstress• NbN film deposit with 12W
RF substrate biasing powerhas biggest film stress andlowest resistivity measured© Oxford Instruments 2022

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Effect of bias on superconducting properties NbN
Comparison of Superconductivity with Different NbN Plasma ALD Solutions•

Lower Room temperature (RT) resistivity usually indicates higher critical temperature Tc•

The plasma ALD solution offered by Oxford Instruments (OIPT) shows excellent performanceeven at low process temperature for NbN deposition
900
800
700
600
500
4003002001000100200300

Deposition Temperature (°C)
© Oxford Instruments 20224001614121086420Tc (K)Resistivity (μΩ*cm)

NbN: Resistivity vs deposition temperature
RT resistivity_OIPT
RT resistivity_Sowa
RT resistivity_Ziegler
Tc_OIPT
Tc_Sowa
Tc_Ziegler

Data quoted from:[1] Ziegler et al., IEEE Transactions on Applied
Superconductivity, Volume 27 , Issue 7 (2017)[2] Sowa et al., J. Vac. Sci. Technol. A (2017)8