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www.DRAFT.ugent.be

A model for magnetron sputter

deposition using a rotating cylindrical

magnetron

K. Van Aeken 1, S. Mahieu 1, R. Persoons2, D. Depla 1

1 UGent, Gent, Belgium

2 VITO, Mol, Belgium

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Magnetron sputter deposition simulations

Requirements

-On the deposited layers :

Thickness and composition uniformity, desired film

properties, …

-On the magnetron :

Target utilization, process stability, power consumption,

…

Optimization through :

-Experiments

-Simulation of the sputter deposition process (virtual

magnetron) :

1) the magnetron discharge

2) the sputtering from the target

3) the transport of the sputtered particles through

the gas phase

Introduction

Model

Discharge

Sputtering

Transport

Experiments

Erosion

Deposition

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Magnetron sputter deposition simulations

Goal : modeling deposition using a small scale rotating cylindrical

magnetron

Introduction

Model

Discharge

Sputtering

Transport

Experiments

Erosion

Deposition

Approach: Test particle Monte Carlo

- Why ?

- fast

- applicable to large geometries (upscalable)

- straightforward implementation

- But :

- no collective behavior

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Discharge : electron & ion transportIntroduction

Model

Discharge

Sputtering

Transport

Experiments

Erosion

Deposition

Predefined

-> Lorentz-force

High energy electron trajectories :

)()(

BvEqdt

vmd

×+=

BE

,

Anomalous transport (Bohm-diffusion)

--> additional randomizing collisions

Sputter gas

--> elastic, exciting and ionizing collisions

Ion trajectories : assumed collisionless

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Discharge : electron & ion transport

1getDP: http://www.geuz.org

B

Introduction

Model

Discharge

Sputtering

Transport

Experiments

Erosion

Deposition

field : sheath model →Child-LangmuirE

Self consistency enforced by the sustainment condition: 1=iNγ

3

2

0 2

4 2

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di

i

Vej

M dε=

Discharge voltage V, pressure p → discharge current I

rotatable : Child-Langmuir Planar : PIC2

2E. Bultinck, PLASMANT, Antwerp, Belgium

Bmax ≈ 1000 G

Pre-sheath dip

Not quite !

field : input value, finite elements1

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SputteringIntroduction

Model

Discharge

Sputtering

Transport

Metal flux

Erosion

Deposition

Heart-like emission

Deviation from cosine

Propose differential yield1 :

∑=

=Ω

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12

2

cos)(i

i

icd

Ydθθ

Fit coefficients ci from the

simulated deposition profiles

of an angular base set

Nascent energy : SRIM

Nascent angular distribution :

[1] K. Van Aeken, S. Mahieu, D. Depla J. Phys. D: Appl. Phys. 41 205307 (2008)

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Gas phase transportIntroduction

Model

discharge

Sputtering

Transport

Experiments

Erosion

Deposition

Assumptions :

sputtered particles are neutral atoms

-> uninfluenced by

only elastic collisions with neutral gas atoms

- ionization degree « 1

- density of sputtered particles « density of gas atoms

Individual collisions :

Interaction potential V(r)

1) screened Coulomb potentials

2) quantum chemical potential for Cu-Ar and Al-Ar2

[1] SImulation of Metal TRAnsport, available at http://www.draft .ugent.be

[2] K.T. Kuwata et al 2003 Nucl. Instr. and Meth. in Phys. Res. B 201 566-70

Advantage : model low energy attractive interaction

+ gas motion → better description of

(near) thermal flux

Implemented in SIMTRA1

BE

,

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Target erosionIntroduction

Model

Discharge

Sputtering

Transport

Experiment

Erosion

Deposition

Measured using optical profilometry :

- cylindrical target mounted on a step motor

- depth profile scanned strip per strip

For accuracy the target depth profile was measured

before sputtering as well -> relative depth = erosion

The magnetic field was varied by changing the vertical (z)-

position of the magnet array with respect to the target

Sputter experiments were carried out under following

conditions :

5560.420.4-10P4

4380.440.4-12P3

3690.440.4-14P2

3690.440.4+14P1

Vd (V)Id (V)P (Pa)Sign(B)z(mm)Name

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Target erosionIntroduction

Model

Discharge

Sputtering

Transport

Experiments

Erosion

Deposition

-10mm

-12mm

-14mm

+14mm

sign(B)z

E Bv ×

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Target erosion

Comparison with simulated erosion profiles :

- simulation : both Vd and Id were externally enforced,

not self consistent (equivalent to tuning the ISEE

coefficient)

integrated

Introduction

Model

Discharge

Sputtering

Transport

Experiments

Erosion

Deposition

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Anomalous transportIntroduction

Model

Discharge

Sputtering

Transport

Experiments

Erosion

Deposition

Bohm-collision

frequency:

B B Lν α ω=

Lω Larmor radius

z = 4mm -> strongest B-field

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Magnetic field dependenceIntroduction

Model

Discharge

Sputtering

Transport

Experiments

Erosion

Deposition

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Deposition rate distribution rotatable magnetron

Measure deposition rate with a

quartz crystal microbalance for :

Cu, Ti, Al target

Ar pressure : 0.3, 0.6 and 1 Pa

as function of θ at :

3 radial distances : r1,r2,r3

3 z-positions : z1,z2,z3

⇒Outward radial metal flux (r,θ,z)

Compare to simulation

Al, 0.3Pa Ar

r = r2, θ = -30°, z = z2

Vd = 357 V, I = 0.45 A

Example :

Introduction

Model

Discharge

Sputtering

Transport

Experiments

Erosion

Deposition

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Deposition rate distribution rotatable magnetronIntroduction

Model

Discharge

Sputtering

Transport

Experiments

Erosion

Deposition

P = 0.3 Pa

r = r1

Spatial dependence Pressure dependence :

r = r1

z = z2

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Thanks for the attention

Simulation code :

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