Modelling thin film growth of transition metal nitridesdraftugentbe.webhosting.be/File/stijn mahieu IVC17_2007.pdf · 2012-07-04 · Modelling thin film growth of transition metal

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Modelling thin film growth of transition metal nitrides

Stijn Mahieu, D. Depla, K. Van Aeken, and R. De Gryse

Ghent University

Funded by the FWO-Flanders

Introduction:w

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Mechanical properties

Optical coating

Diffusion barrier for Al or Cu interconnects

Biocompatible overlayer

all influenced by the

crystallographic

orientation

Reactive magnetron sputter deposition of TiN

IntroductionTrendsThin Film Growth

Zone Ia&bZone IcZone TZone IIESZMConclusions

More resultsEnergy fluxDiffusion rateDiffusion lengthConclusions

General trends in out-of-plane orientation:-Influence of film thickness: [200] => [111]often explained by the “minimisation of overallenergy” model e.g. Pelleg, Oh, Je...

Abadias and Tse, JAP 95 (2004)

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eIntroductionTrendsThin Film Growth




Hultman, JAP 78 (1995)

[111]

[200]

-Influence of the ion-to-atom ratio: [111] => [200]often explained by “kinetics” or “diffusion rates”

e.g. Greene, Hultmann, Gall,...

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-Influence of the ion-to-atom ratio: [111] => [200]often explained by “kinetics” or “diffusion rates”

e.g. Greene, Hultmann, Gall,...

=> Extended Structure Zone ModelMahieu, PhD. Thesis

-Influence of the N2-flow: random => [111] =>[200]

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Thin film growth:

Movchan-Demchishin1969

Thornton1974

Messier et. al1984

Grovenor et. al1984

Microstructure as a function of mobility: Structure Zone Modelw

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Thin film growth:Microstructure as a function of mobility: Extended Structure Zone Model

substrate substrate substrate

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S. Mahieu et al: TSF 515 (2006) 1229 ww

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Thin film growth:

��=> Nucleation of crystalline islands

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Plane with lowest perpendicular growth rate survive

high growth ratelow growth rate

=> faceting occurs due to growth rate anisotropy of crystallographic planes

Microstructure as a function of mobility: Extended Structure Zone Modelw

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Zone Ic: growth rate anisotropy

Perpendicular growth rate � sticking coefficient Sc

Hartman-Perdok theory1:

sticking coefficient �number of nearest neighbours between adparticle and growing plane

1: e.g. P. Hartman and W.G. Perdok: Acta. Cryst. 8 (1955)

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2: H.Huang et al. J. Appl. Phys.84 (1998) 3636

2:

high adparticle mobility

� high lateral growth rate

� low perpendicular growth rate

Huang2: adparticle mobility �number of nearest neighbours between adparticle and growing plane

Number of nearest neighbours influenced by- adparticle Ti or TiN- reactive gas: N or N2

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Zone Ic: growth rate anisotropy

crystallographic plane with lowest perpendicular growth rate=

lowest number of nearest neighbours

345NTiN342N2TiN345NTi321N2Ti

{111}{110}{100}

number of nearest neighbours onthe plane:

state of the reactive gas

adparticles

{111}{100}{111}{100}

faceting

� {100} or {111} faceting due to growth rate anisotropy

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Hit & stickno mobilityamorphous

Zone Ic: no adparticle diffusion from one grain to another

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Zone T: adparticle diffusion from one grain to another

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allowed

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Zone T: overgrowth

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Grain with most tilted facet slowly envelops and thus overgrows other grain.

This corresponds to grains with geometric fastest growing direction perpendicular to substrate

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{100} faceting: [111] orientation, {111} faceting: [100] orientationww

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Zone II: recrystallization during grain growthw

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Zone II: recrystallization during grain growth

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island diffusion

grain boundary migration

ESZM overview: influence of N2-flow

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S. Mahieu et al.: TSF 515 (2006) 1229-1249

Zone Ic

Zone T

Zone II200

175

150

125

100

75

50

ener

gy fl

ux (

eV/T

i)

181512963N2-flow (sccm)

1600

1400

1200

1000

800

600

400

200

0

Cps

(a.

u.)

50454035302θ (°)

[111] [200] S.S.

3 sccm N2

5 sccm N2

7.5 sccm N2

10 sccm N2

14 sccm N2

17 sccm N2

20 sccm N2

Zone Ic

Zone T

Zone II

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[111] N2[100] N

[100]

ESZM overview: influence of film thickness


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S. Mahieu et al.: TSF 515 (2006) 1229-1249

Abadias and Tse, JAP 95 (2004)

Zone T: evolutionary selection

[100]

[100]

[100]+[111]

[111]~250 nm

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[111] N2[100] N

[100]

ESZM overview: influence of ion-to-atom ratio

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S. Mahieu et al.: J. Cryst. Growth.279 (2005) 100-109 (adapted version!!!!)

Hultman, JAP 78 (1995)

[111]

[200]

N-atoms due to plasma dissociation and collisional dissociation of N2+ ions

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[111] N2[100] N

[100]

Conclusion out-of-plane orientation

� Microstructure and out-of-plane orientation understood after

- calculation of energy flux towards growing film (mobility)

- measurement of plasma composition(atomic/molecular reactive gas)

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More results: influence of T-S distance and N2-flow on orientation

1.0

0.8

0.6

0.4

0.2

0.0

fract

ion

15 c

m

181512963

1.0

0.8

0.6

0.4

0.2

0.0

fract

ion

13 c

m

1815129631.0

0.8

0.6

0.4

0.2

0.0

fract

ion

11 c

m

181512963

1.0

0.8

0.6

0.4

0.2

0.0

fract

ion

11 c

m

181512963N2-flow (sccm)

0.8

0.6

0.4

0.2

0.0

fract

ion

7 cm

181512963N2-flow (sccm)

15 cm 13 cm

11 cm 9 cm

'111' '200' '220'

7 cm

Out-of-plane orientation changes between random, [111],[200]

Relation with energy flux per Ti particle Θ ?ww

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1600

1400

1200

1000

800

600

400

200

0

Cps

(a.u

.)

50454035302θ (°)

[111] [200] S.S.

3 sccm N2

5 sccm N2

7.5 sccm N2

10 sccm N2

14 sccm N2

17 sccm N2

20 sccm N2

Modeling energy flux towards substrate

-Condensation energy: Ti (s) +1/2 N2 (g) => TiN (s)

-Kinetic energy of sputtered Ti particles: binary collisionMonte Carlo simulation + SRIM + PPM

-Kinetic energy of reflected and neutralized ions: binarycollision Monte Carlo simulation + SRIM + PPM

-Energy of electrons: Langmuir probe measurements

-Energy from plasma contribution

-Metallic flux of Ti: PPM + quartz crystal oscillator

Detailed measurement and calculation method in S. Mahieu et al: in preparationw

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Energy flux: influence of T-S distance and N2-flow

Detailed measurement and calculation method in S. Mahieu et al: in preparation

Energy flux per deposited Ti partilce (Θ) increases withN2-flow and with T-S distance

Diffusion rate of adparticles

with Eb the barrier needed to allow:- intergrain diffusion (zone Ic=> zone T) Eb = Egb

- recrystallization during grain growth (zone T=> zone II) Eb = Erecryst

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240

200

160

120

80

40en

ergy

e flu

x/Ti

(Θ) (

eV/T

i)

181512963N2-flow (sccm)

T-S distance 15 cm

13 cm

11 cm

9 cm

7 cm

( )Θ−�

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�� −

≅≅1

eeD kTEb

Diffusion rate: influence of T-S distance and N2-flow

Substrate

E > Egb

Intergrain diffusion:

Substrate Substrate Substrate Substrate

Recrystallization during grain growth:

Zone Ic

Zone T

Zone IIw

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1.000

0.995

0.990

0.985

0.980

diffu

sion

rate

(~ex

p(1/

Θ)(

a.u.

)

181512963N2-flow (sccm)

random [111] 50%[111], 50%[200] [200]

T-S 7 cmT-S 9 cmT-S 11 cmT-S 13 cmT-S 15 cm

intergrain diffusion

recrystallization during grain growth

Diffusion length: influence of T-S distance and N2-flow

Substrate

Difussion lengthL too short

Difussion length L:

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1.0

0.8

0.6

0.4

0.2

difu

ssio

n le

ngth

(~sq

rt(ex

p(-1

/Θ)/R

d) (a

.u.)

181512963N2-flow (sccm)

random [111] 50% [111], 50% [200] [200]

T-S 7 cm

T-S 9 cm

T-S 11 cm

T-S 13 cm

T-S 15 cm

E>EgbΛ<�

d

E

RetDLb �

��

��

Θ−

≅∗≅ )(

Transitions Zone Ic/zone T/zone IIw

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1.0

0.8

0.6

0.4

0.2

difu

ssio

n le

ngth

(~s

qrt(e

xp(-

1/Θ

)/Rd)

(a.

u.)

181512963N2-flow (sccm)

random [111] 50% [111], 50% [200] [200]

T-S 7 cm

T-S 9 cm

T-S 11 cm

T-S 13 cm

T-S 15 cm

Zone Ic=>zone T-high diffusion length (L>Λ)-high diffusion rate(E>Egb)

1.000

0.995

0.990

0.985

0.980

diffu

sion

rate

(~ex

p(1/

Θ)(

a.u.

)

181512963N2-flow (sccm)

random [111] 50%[111], 50%[200] [200]




Transitions Zone Ic/zone T/zone IIw

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1.0

0.8

0.6

0.4

0.2

difu

ssio

n le

ngth

(~sq

rt(ex

p(-1

/Θ)/R

d) (a

.u.)

181512963N2-flow (sccm)

random [111] 50% [111], 50% [200] [200]

T-S 7 cm

T-S 9 cm

T-S 11 cm

T-S 13 cm

T-S 15 cm

Zone T=>zone II-high diffusion rate(E>Erecryst)recrystallization by grain boundary migration

1.000

0.995

0.990

0.985

0.980

diffu

sion

rate

(~ex

p(1/

Θ)(

a.u.

)

181512963N2-flow (sccm)

random [111] 50%[111], 50%[200] [200]




Conclusions:


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Development of microstructure understood if:

-Diffusion rate and length are calculated from energy flux Θ

-In zone T: plasma composition is known

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International Conference on Thin Films 14

www.ICTF14.ugent.be

17-20 November 2008

‘t Pand, Ghent, Belgium

[email protected]

Documents

Modelling thin film growth of transition metal nitridesdraftugentbe.webhosting.be/File/stijn mahieu IVC17_2007.pdf · 2012-07-04 · Modelling thin film growth of transition metal