HiPIMS: technology, physics and thin film applications.

HiPIMS: technology, physics and thin film applications
Tiberiu MINEA
Laboratoire de Physique des Gaz et Plasmas – LPGP UMR 8578 CNRS, Université Paris-Sud, 91405 Orsay Cedex, France
tiberiu.minea@u-psud.fr

PARIS
SACLAY
PALAISEAU
Triangle of Physics
ORSAY
Université Paris-Sud
T. Minea
2
PSE 2012 // September 12, 2012
Université Paris-Saclay
ORSAY

Diffusion and residence time: example
The residence time were determined by
placing individual monomers on different sites
(islands/terrace).
By repeating the experiments 600
times it was found that τs is much
larger at step edges (stronger bonding)
R. Ganapathy et al., Science 327, 445 (2010)
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Kinetic roughening
The ideal step flow (layer-by-layer) growth is seldom found in
experiments, instead we often encounter islands leading to surface
roughening.
H. Huang et al., J. Appl. Phys. 84, 3636 (1998)
Simulation of Al deposited on a flat foreign
substrate for two different microstructures: (top)
{111}, (bottom) {100}. An area of 20x20 nm is
shown (dep. rate 10 μm/min)
Kinetic roughening in an MBE experiment
Pt/Pt(111). Very slow dep. rate 2.7 Å/min at
167°C. An area of 390x390 nm is shown.
J. Krug et al., Phys. Rev B 61, 14037 (2000)
XIII Brazilian T. Minea MRS - Symposium N / 29 September 2014 4

Microstructure: structure zone models
In order to be able to say if we have good film quality or not we need to
look at the microstructure and use our understanding of film formation.
A schematic representation of the microstructure can be found using structure zone models (SZM),
where the use of reduced temp. scale makes the model generally applicable for different materials.
Zone I: Columnar and porous structure with a rough surface, due to low adatom mobility
Zone T: Columnar, quite dense structure with a smoother surface, increased adatom mobility:
competitive grain growth (but little grain boundary mobility)
Zone II: Columnar, dense structure with a rather smooth surface; both adatom and grain boundary
mobility (recrystallization)
Ts =300 K
Ts =100 K
F.H. Baumann et al., MRS Bulletin 26, 182 (2001)
I. Petrov et al., J. Vac. Sci. Technol. A 21, S117 (2003)

Low surface mobility
Ts = 500 °C
P = 38 mTorr
Ji/JTi = 0.5
Ei = 100 eV
Ts = 300 °C
P = 5 mTorr
Ji/JTi = ~1
Ei = 20 eV
6
Zone 1: Zone T:
XIII Brazilian T. Minea MRS - Symposium N / 29 September 2014

Results of ion bombardment
Let us start with the end results first in order to see the bigger picture.
Stepwise we will break down the physics and learn how to tailor and
optimize the ion bombardment.
Ts = 350 °C
P = 20 mTorr
Ji/JTa = 1.3
Ei = 20 eV
Ts = 350 °C
P = 20 mTorr
Ji/JTa = 10.7
Ei = 20 eV
Ex) TaN grown by
DCMS in a UHV
system.
The ratio of incoming
ions (no distinction
between gas and metal
ions!) to incoming metal
neutrals was changed
while maintaining the
energy of the incoming
ions.
In these bright-field
plan-view TEM images
of 500 nm thick coatings
we observe dramatic
changes in
microstructure.

Precursor ionization, is it possible?
XIII Brazilian MRS - Symposium N / 29 September 2014
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1.Electrostatic confinement; e.g. hallow cathode
2.Magnetic confinement; e.g. magnetic bottle
3.Magnetron plasma
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YES, if precursors are ionized BEFORE deposition!
How?
Increasing plasma density!
Inspired by A. Anders, 2013

Outline
9
1.HiPIMS technology
2.HiPIMS magnetron plasma modelling (OHIPIC, I-OMEGA)
3.Thin Films by HiPIMS
4.Conclusions
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From Conventional Magnetron to HiPIMS
Film growth
Particle transport
D.J. Christie, J V S T A 23, 330 (2005) D Lundin et al., P S S T 18, 045008 (2009)
Ionization of sputtered spieces
Gas dynamics
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Sputtering
+

V. Kouznetsov , U. S. Patent No. 6,296, 742 B 1 (2001)
 Pulsed power supply: 0.1 – 1 kHz, 200 A, 1 kV
 Pulse width: ~100 s
 Pulse power: 50 kW
 Typical mean power: 500 W
HiPIMS power supply
HiPIMS
First Pulsed generator concept
DC - CMS
11
SINEX 3 power supply by PlasmAdvance
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HiPIMS = High Voltage & High Current!
High Power Impulse Magnetron Sputtering

HiPIMS pulses in reactive gas mixture
12
Current waveforms for long pulses
Ar/O2 mixture, 0.5 Pa
Pulse width 200 μs
(a) 50 Hz
(b) 5 sccm
M. Hála et al., J. Phys. D: Appl. Phys (2012)
(b)
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Self-sputtering  high current, but… limited deposition rate!
Very long pulses (> 300 μs)
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A. Anders et al., J. Appl. Phys. 103 (2008)
Argon

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Back-attraction & self-sputtering
Strong Ez → Steep potential hill for M+
A. Mishra et al., Plasma Sources Sci. Technol. 19, 045014 (2010)
M
+
Ez

How couple the HiPIMS power?
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DC – overshot of the voltage at the beginning, called breakdown voltage (Vbk > Vdisch)
RF – impedance matching system
HiPIMS: Pulsed, keeping high voltage and high current
Pre-ionization before pulse
Why pre-ionization?
Plasma gas conductivity is already established, i.e. no impedance jump
Fast current rise  possibility to operate with narrow pulses

Pulse time [μs]
Ganciu et al, US Patent No. 7, 927, 466 B2 (19 April 2011)
Fast HiPIMS with pre-ionization
 Average Power 80 W
 Pulse width ~10 μs
 Frequency < 1kHz
 Umax ~ 1kV
 Imax ~ 100 A
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SHORT & FAST Pulsed generator concept [2]; developed 2004
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Effect of reactive gases
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Current waveforms for short pulses
D. Benzeggouta et al., P S S T (2009)
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5 Pa
0.5Pa
Ar/O2 mixture; HiPIMS with pre-ionization; 10 μs, 50 Hz

HiPIMS advantages and drawbacks
advantages
drawbacks
•Back-attraction to the target of ionized sputtered species
•Lower deposition rate with respect to DC, at equivalent average power
•Start and operation at very low pressure are difficult issues (p < 0.2 Pa)
High plasma density => high ionization degree of the sputtered material
Fast rise-up of both high voltage and high current 10 Aμs-1
Operation at low pressure (p > 0.4 Pa)
High sputtering yield, despite the low duty-cycle, « time on » / « time off »
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Other types of pulses
Modulated Pulse Power
(MPP)
P.M. Barker et al., JVST A31 (2013)
t
J. Lin et al.,
Surf. Coat. Technol. 203,(2009)
O. Antonin et al.,
J Phys. D: Appl. Phys (submitted)
chopped HiPIMS
(c-HiPIMS)
multi HiPIMS
(m-HiPIMS)
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c-HiPIMS versus m-HiPIMS
choped-HiPIMS
Single pulse 1x50 μs
Single pulse 1x250 μs
Multi-pulse 5x50 μs
O. Antonin et al., J Phys. D: Appl. Phys (submitted)
multi-HiPIMS
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푰풑풖풍풔풆(ퟓퟎμ풔) ퟓ 풊=ퟏ >푰풔풊풏품풍풆 (ퟓ×ퟓퟎμ풔)

m-HiPIMS specificities
COST Action MP-0804, HIPP Processes, O.Antonin, V.Tiron, C.Costin, G.Popa, T.Minea, 2013
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t
-1kV
-200V
TOFF
Afterglow
ion
diffusion
Pulse
ON
Dense
Plasma
Periodic Sequence characterized by the
triplet (tμon , tμoff , n)
pulse width, time off number of pulses between pulses in the sequence
O. Antonin et al., J Phys. D: Appl. Phys (submitted)

Dual magnetron HiPIMS/RF
Challenges
•Clean room operation
•Very low pressure operation (< 0.1 Pa, UHV)
•No perturbation of the RF system
•Homogeneous thin film
•Uniform on 4” Si substrate
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N. Holtzer et al., Surf. Coat. & Technol. 250 (2014) 32

Dual HiPIMS/RF advantage
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Pressure effect, without RF
RF effect at 0.1 Pa
HiPIMS is always taking advantage of gas (pre-)ionization, here induced by the RF
Dual HiPIMS/RF deposition process can operate at lower pressures than HiPIMS alone (e.g. 0.05 Pa)
HiPIMS/RF successful operation in reactive atmosphere (Ar/N2)
RF assisted HiPIMS requires lower or even no pre-ionization

Outline
24
1.HiPIMS technology
4.Conclusions
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Magnetron target - 2D configuration
Tiberiu MINEA, Adrien REVEL, Claudiu COSTIN
Geometry (x, z)
Simulation volume: 2 x 2.5 cm2
Grids: 201 x 512 ÷ 401 x 2048
Cell dimensions: Dx, Dz = 10 m !!!
8 million simulation particles
Control parameters
Time step: Dt = 5 x 10-12 s ÷ 5 x 10-13 s
Simulated real time: 15 μs !!!
25
Debye length
ne > 1013 cm-3 > 1019 m-3
le  10 μm (Te = 4eV)
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HiPIMS current
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0 2 4 6 8 10
Pulse time [μs]
OHIPIC: Orsay HIgh density plasma Particle-In-Cell model
Experiment using fast pre-ionization HiPIMS
OHIPIC model simulated discharge current
0 1 2 3 4 5 6
Pulse time [μs]
0
-300
- 600
Voltage (V)
Current
T. Minea et al, Surf. Coat. Tech. 255, (2014) 52
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T. Minea et al, Surf. Coat. Tech. (2014), Available online 5 December 2013
2D maps of charged particles by OHIPIC
XIII Brazilian MRS - Symposium N / 29 September 2014 27
20 15 10 5 0 5 10 15 20
0
5
10
15
20
25
e- density (cm-3
)
1.0E6 1.7E10 3.4E10 5.1E10 6.8E10 8.5E10
x (mm)
z (mm)
Ar+ density (cm-3
)
20 15 10 5 0 5 10 15 20
0
5
10
15
20
25
Ar+ density (cm-3
) e- density (cm-3
)
1.0E6 1.6E11 3.3E11 4.9E11 6.6E11 8.2E11
x (mm)
z (mm)
20 15 10 5 0 5 10 15 20
0
5
10
15
20
25
Ar+ density (cm-3
)
1.0E6 9.4E11 1.9E12 2.8E12 3.8E12 4.7E12
e- density (cm-3
)
x (mm)
z (mm)
A (75 ns); ne = 8 x 1016 m-3 B (2 μs); ne = 8 x 1017 m-3 C (3 μs); ne = 5 x 1018 m-3
 Electron density increases x 100 in 3 μs !!!
 Much localized high density
 Larger dense plasma=> larger race-track
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a posteriori Monte Carlo - code OMEGA
1.Define a domain (sputter chamber)
2.Generate sputtered particles one by one randomly from a probability distribution (SED + SAD)
3.DCMS: Particle collision with process gas
4.Analyze the particle’s velocity, direction, …
OMEGA summary
 3D treatment of elastic collisions
 Ti/Ar DCMS discharge
 No Ti-Ti collisions
 No gas rarefaction
3D Metal modelling
OMEGA: Orsay MEtal transport in GAses model
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T. Minea et al, Surf. Coat. Tech. 255, (2014) 52
0 1 2 3 4 5 6
-600
-400
-200
0
C (3.0 s)
B (2.0 s)
Cathode voltage (V)
t (s)
A (75 ns)
Short pulse
Pre-ionization
A (75 ns)
B (2 μs)
C (3 μs)
Degree of Metal Ionization in HiPIMS
 HiPIMS self-consistent simulated by OHIPIC code
 Density maps for the three representative instants of the pulse
 a posteriori MC very useful and powerful
 Fast estimation of the ionization fraction of
sputtered vapour and metal ion back-attraction
I-OMEGA for HiPIMS
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Outline
30
1.HiPIMS technology
4.Conclusions
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HiPIMS thin film deposition @ LPGP
31
-
Ti/TiN; Ta/TaN
Ta3N5
T. Minea XIII Brazilian MRS - Symposium N / 29 September 2014
straddles H2 and O2
evolution potential
Maeda et al., J. Phys. Chem. C 111, 2007.
Archer, J. Appl. Electrochem. 5, 1975.
 Energy storage
applications

Ta-N films for photoelectrolysis
32
Early saturation at Ta3N5 at low N2 partial pressure in Ar
N
Ta
O
Rutherford BackScattering (Coulombic collisions)
Nuclear Reaction Analysis
RBS / NRA
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by HiPIMS

HiPIMS Ta-N films for photoelectrolysis Film density
Low pressure samples
Transition from ρTa, ρTaN to ρTa3N5
Dense film
High pressure samples
constant density below ρTa3N5
Porous film
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200 nm
Porous, columnar
~ 13 nm
200 nm
Dense, homogeneous
M.Rudolph and al, EMRS 2014; M.Rudolph and al., IAP 2014
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Atomic shadowing
Conventional magnetron experiment using Cu target, where:
(left) Ar is used as sputtering gas, i.e. low ratio of metal ions compared to neutrals, resulting in atomic shadowing and bad wall coverage.
(right) Cu is sputtering Cu (self- sputtering) meaning a much higher ratio of Cu ions. Here better wall coverage is achieved and one needs less material to completely cover the trench with a Cu coating.
Cu neutrals
Cu ions
Z. J. Radzimski, J. Vac. Sci. Technol. B 16, 1102 (1998)
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Microelectronics applications

Ultravacuum Co-sputtering reactor
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Si/Nb
Dual HiPIMS/RF
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Bolometer matrixes
•High sensitivity calorimeters
•Superconducting transition edge sensors coupled to calorimeter
amorphous

Superconducting transition of Si/Nb
37
by Dual HiPIMS/RF
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Bolometer matrixes
• NbSi thin films alloy perform excellent transition edge at 3 mK with Tc and Resistance adjustable with temperature.
• Promising alternative to both e-beam evaporation and MS-PVD for large area bolometers applications in astrophysics.

Conclusions
 HiPIMS is an emerging technology with very high applicative potential: - particle and film nano-structuring - better control of the energy deposited during the growth - better stability and stoichiometry control, etc.
Diagnostic and modelling give today a better understanding of the HiPIMS physics, space and time evolution of plasmas species and energy carried to the growing film
Compatible with Clean Room requirements and already successful
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 Claudiu COSTIN
 Catalin VITELARU
 Vasile TIRON
Contributors
France
Romania
 Lise CAILLAULT
 Marie-Christine HUGON
 Brigitte BOUCHER
 Jean BRETAGNE
 Daniel LUNDIN
 Adrien REVEL
 Martin RUDOLF
 Olivier ANTONIN
 Nils BRENING
 Daniel LUNDIN
39
Sweden
Thanks you all for your attention!
T. Minea

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T. Minea
December 9-11 2015 Paris, France
4th MIATEC – Magnetron, Ion processing & Arc Technologies European Conference
14th RSD - International Conference on Reactive Sputter Deposition
DC - CMS
Scientific joint event in Paris at the CNAM Conservatoire National des Arts et Métiers
since 1794
Social event: Visit of the « Arts and Science Museum »

Many THANKS to
Interuniversity Attraction Poles (IAP)
Phase VII - P7/34
T. Minea

HiPIMS: technology, physics and thin film applications.

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HiPIMS: technology, physics and thin film applications.