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 [email protected]

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)

3 XIII Brazilian MRS - Symposium N / 29 September 2014 T. Minea

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 MRS - Symposium N / 29 September 2014 4 T. Minea

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:


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 8

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


1. HiPIMS technology

2. HiPIMS magnetron plasma modelling

(OHIPIC, I-OMEGA)

3. Thin Films by HiPIMS

4. Conclusions

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XIII Brazilian MRS - Symposium N / 29 September 2014

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

10 T. Minea

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 XIII Brazilian MRS - Symposium N / 29 September 2014

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


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)

T. Minea XIII Brazilian MRS - Symposium N / 29 September 2014 13

A. Anders et al., J. Appl. Phys. 103 (2008)

Argon


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?


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 16

SHORT & FAST Pulsed generator concept [2]; developed 2004

XIII Brazilian MRS - Symposium N / 29 September 2014 T. Minea

Effect of reactive gases


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 »

18 T. Minea XIII Brazilian MRS - Symposium N / 29 September 2014

19

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)

T. Minea XIII Brazilian MRS - Symposium N / 29 September 2014

20

c-HiPIMS versus m-HiPIMS

choped-HiPIMS


Single pulse 1x50 µs

Single pulse 1x250 µs

Multi-pulse 5x50 µs


multi-HiPIMS


𝑰𝒑𝒖𝒍𝒔𝒆(𝟓𝟎µ𝒔)

𝟓

𝒊=𝟏

> 𝑰𝒔𝒊𝒏𝒈𝒍𝒆 (𝟓 × 𝟓𝟎µ𝒔)

m-HiPIMS specificities

COST Action MP-0804, HIPP Processes, O.Antonin, V.Tiron, C.Costin, G.Popa, T.Minea, 2013


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



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


N. Holtzer et al., Surf. Coat. & Technol. 250 (2014) 32

Dual HiPIMS/RF advantage



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




(OHIPIC, I-OMEGA)


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 !!!


Debye length ne > 1013 cm-3 > 1019 m-3

le 10 µm (Te = 4eV)

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HiPIMS current


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

Vo

ltag

e (

V) Current

T. Minea et al, Surf. Coat. Tech. 255, (2014) 52

T. Minea

T. Minea et al, Surf. Coat. Tech. (2014), Available online 5 December 2013

2D maps of charged particles by OHIPIC


20 15 10 5 0 5 10 15 200

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 15 200

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 15 200

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


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)

Ca

tho

de

vo

lta

ge

(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




(OHIPIC, I-OMEGA)


4. Conclusions

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HiPIMS thin film deposition @ LPGP

31

-

Ti/TiN; Ta/TaN

Ta3N5


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


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

33

200 nm Porous, columnar

~ 13 nm

200 nm Dense, homogeneous

M.Rudolph and al, EMRS 2014; M.Rudolph and al., IAP 2014


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)


Microelectronics applications

Ultravacuum Co-sputtering reactor

36

Si/Nb Dual HiPIMS/RF


Bolometer matrixes

• High sensitivity calorimeters

• Superconducting transition edge sensors coupled to calorimeter

amorphous

Superconducting transition of Si/Nb

37

by Dual HiPIMS/RF


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

38 XIII Brazilian MRS - Symposium N / 29 September 2014 T. Minea

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


Sweden

Thanks you all for your attention!

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

Science

minea mrs symposium

mrs bulletin

high voltage high current

s pulse power

high power impulse magnetron

pulsed power supply

p s s t

high currentpreionization