Upload
others
View
9
Download
0
Embed Size (px)
Citation preview
www.DRAFT.ugent.be
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
ww
.dra
ft.u
gent
.be
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)
ww
w.d
raft
.uge
nt.b
eIntroductionTrendsThin 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...
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,...
ww
w.d
raft
.uge
nt.b
eIntroductionTrendsThin 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...
-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]
ww
w.d
raft
.uge
nt.b
eIntroductionTrendsThin Film Growth
Zone Ia&bZone IcZone TZone IIESZMConclusions
More resultsEnergy fluxDiffusion rateDiffusion lengthConclusions
Thin film growth:
Movchan-Demchishin1969
Thornton1974
Messier et. al1984
Grovenor et. al1984
Microstructure as a function of mobility: Structure Zone Modelw
ww
.dra
ft.u
gent
.be
IntroductionTrendsThin Film Growth
Zone Ia&bZone IcZone TZone IIESZMConclusions
More resultsEnergy fluxDiffusion rateDiffusion lengthConclusions
Thin film growth:Microstructure as a function of mobility: Extended Structure Zone Model
substrate substrate substrate
������� ����������� ���������� ����
substratesubstrate
������� ����
������� ����
����� ������������������� ��������������
� ������ �
���� �����
�����������
����� ������� ��� ��������������
�����������
� ������������
�������������
������� �����
���� ����
� ������������
�������������
������ ����� �
����Hit & stickno mobilityamorphous
S. Mahieu et al: TSF 515 (2006) 1229 ww
w.d
raft
.uge
nt.b
eIntroductionTrendsThin Film Growth
Zone Ia&bZone IcZone TZone IIESZMConclusions
More resultsEnergy fluxDiffusion rateDiffusion lengthConclusions
substrate substrate substrate
������� ����������� ���������� ����
substratesubstrate
������� ����
������� ����
����� ������������������� ��������������
� ������ �
���� �����
�����������
����� ������� ��� ��������������
�����������
� ������������
�������������
������� �����
���� ����
� ������������
�������������
������ ����� �
����
Thin film growth:
���������=> Nucleation of crystalline islands
���������
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
ww
.dra
ft.u
gent
.be
IntroductionTrendsThin Film Growth
Zone Ia&bZone IcZone TZone IIESZMConclusions
More resultsEnergy fluxDiffusion rateDiffusion lengthConclusions
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)
1:w
ww
.dra
ft.u
gent
.be
IntroductionTrendsThin Film Growth
Zone Ia&bZone IcZone TZone IIESZMConclusions
More resultsEnergy fluxDiffusion rateDiffusion lengthConclusions
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
����������������������
!��"
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
#$$!%#!!!%
�"
#!!$%
�"
#$$!%
#!!$%
#!$$%
ww
w.d
raft
.uge
nt.b
eIntroductionTrendsThin Film Growth
Zone Ia&bZone IcZone TZone IIESZMConclusions
More resultsEnergy fluxDiffusion rateDiffusion lengthConclusions
substrate substrate substrate
������� ����������� ���������� ����
substratesubstrate
������� ����
������� ����
����� ������������������� ��������������
� ������ �
���� �����
�����������
����� ������� ��� ��������������
�����������
� ������������
�������������
������� �����
���� ����
� ������������
�������������
������ ����� �
����
Hit & stickno mobilityamorphous
Zone Ic: no adparticle diffusion from one grain to another
���������
� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � �� � � � � � � � �� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � �� � �� � � � � � � � � � � � � � �
���������
Not allowed
ww
w.d
raft
.uge
nt.b
eIntroductionTrendsThin Film Growth
Zone Ia&bZone IcZone TZone IIESZMConclusions
More resultsEnergy fluxDiffusion rateDiffusion lengthConclusions
substrate substrate substrate
������� ����������� ���������� ����
substratesubstrate
������� ����
������� ����
����� ������������������� ��������������
� ������ �
���� �����
�����������
����� ������� ��� ��������������
�����������
� ������������
�������������
������� �����
���� ����
� ������������
�������������
������ ����� �
����
Hit & stickno mobilityamorphous
Zone T: adparticle diffusion from one grain to another
���������
�� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � ��� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � �
allowed
ww
w.d
raft
.uge
nt.b
eIntroductionTrendsThin Film Growth
Zone Ia&bZone IcZone TZone IIESZMConclusions
More resultsEnergy fluxDiffusion rateDiffusion lengthConclusions
Zone T: overgrowth
�������������� ��
Grain with most tilted facet slowly envelops and thus overgrows other grain.
This corresponds to grains with geometric fastest growing direction perpendicular to substrate
#$$!%#!!!%
�"
#!!$%
�"
#$$!%
#!!$%
#!$$%
{100} faceting: [111] orientation, {111} faceting: [100] orientationww
w.d
raft
.uge
nt.b
eIntroductionTrendsThin Film Growth
Zone Ia&bZone IcZone TZone IIESZMConclusions
More resultsEnergy fluxDiffusion rateDiffusion lengthConclusions
substrate substrate substrate
������� ����������� ���������� ����
substratesubstrate
������� ����
������� ����
����� ������������������� ��������������
� ������ �
���� �����
�����������
����� ������� ��� ��������������
�����������
� ������������
�������������
������� �����
���� ����
� ������������
�������������
������ ����� �
����
Hit & stickno mobilityamorphous
Zone II: recrystallization during grain growthw
ww
.dra
ft.u
gent
.be
IntroductionTrendsThin Film Growth
Zone Ia&bZone IcZone TZone IIESZMConclusions
More resultsEnergy fluxDiffusion rateDiffusion lengthConclusions
substrate
substrate substrate substrate
������� ����������� ���������� ����
substratesubstrate
������� ����
������� ����
����� ������������������� ��������������
� ������ �
���� �����
�����������
����� ������� ��� ��������������
�����������
� ������������
�������������
������� �����
���� ����
� ������������
�������������
������ ����� �
����
Hit & stickno mobilityamorphous
Zone II: recrystallization during grain growth
� � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � � �ww
w.d
raft
.uge
nt.b
eIntroductionTrendsThin Film Growth
Zone Ia&bZone IcZone TZone IIESZMConclusions
More resultsEnergy fluxDiffusion rateDiffusion lengthConclusions
���������
���������
���������
ripening
island diffusion
grain boundary migration
ESZM overview: influence of N2-flow
� ��������������
�����������
� ��������������
�����������
substrate substrate substrate
������� ����������� ���������� ����
substratesubstrate
������� ����
������� ����
����� ������������������� ��������������
� ������ �
���� �����
�����������
����� ������� ��� ��������������
�����������
� ������������
�������������
������� �����
���� ����
� ������������
�������������
������ ����� �
����
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
ww
w.d
raft
.uge
nt.b
eIntroductionTrendsThin Film Growth
Zone Ia&bZone IcZone TZone IIESZMConclusions
More resultsEnergy fluxDiffusion rateDiffusion lengthConclusions
[111] N2[100] N
[100]
ESZM overview: influence of film thickness
substrate substrate substrate
������� ����������� ���������� ����
substratesubstrate
������� ����
������� ����
����� ������������������� ��������������
� ������ �
���� �����
�����������
����� ������� ��� ��������������
�����������
� ��������������
�����������
� ��������������
�����������
� ������������
�������������
������� �����
���� ����
� ������������
�������������
������ ����� �
����
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
ww
w.d
raft
.uge
nt.b
eIntroductionTrendsThin Film Growth
Zone Ia&bZone IcZone TZone IIESZMConclusions
More resultsEnergy fluxDiffusion rateDiffusion lengthConclusions
[111] N2[100] N
[100]
ESZM overview: influence of ion-to-atom ratio
� ��������������
�����������
� ��������������
�����������
substrate substrate substrate
������� ����������� ���������� ����
substratesubstrate
������� ����
������� ����
����� ������������������� ��������������
� ������ �
���� �����
�����������
����� ������� ��� ��������������
�����������
� ������������
�������������
������� �����
���� ����
� ������������
�������������
������ ����� �
����
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
������������������������������ ������
�������������������������� �����������������������
�� ��������&�����
'
��&��#!$$%
(��� �������� ��)����� &"'
*���� ���� ��)����� &"
*������ ��"
*����� ���� ��&"
#!!!%
#!$$%
#!$$%
#!!!%
ww
w.d
raft
.uge
nt.b
eIntroductionTrendsThin Film Growth
Zone Ia&bZone IcZone TZone IIESZMConclusions
More resultsEnergy fluxDiffusion rateDiffusion lengthConclusions
[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)
ww
w.d
raft
.uge
nt.b
eIntroductionTrendsThin Film Growth
Zone Ia&bZone IcZone TZone IIESZMConclusions
More resultsEnergy fluxDiffusion rateDiffusion lengthConclusions
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
w.d
raft
.uge
nt.b
eIntroductionTrendsThin Film Growth
Zone Ia&bZone IcZone TZone IIESZMConclusions
More resultsEnergy fluxDiffusion rateDiffusion lengthConclusions
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
ww
.dra
ft.u
gent
.be
IntroductionTrendsThin Film Growth
Zone Ia&bZone IcZone TZone IIESZMConclusions
More resultsEnergy fluxDiffusion rateDiffusion lengthConclusions
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
ww
w.d
raft
.uge
nt.b
eIntroductionTrendsThin Film Growth
Zone Ia&bZone IcZone TZone IIESZMConclusions
More resultsEnergy fluxDiffusion rateDiffusion lengthConclusions
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−�
��
��� −
≅≅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
ww
.dra
ft.u
gent
.be
IntroductionTrendsThin Film Growth
Zone Ia&bZone IcZone TZone IIESZMConclusions
More resultsEnergy fluxDiffusion rateDiffusion lengthConclusions
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:
ww
w.d
raft
.uge
nt.b
eIntroductionTrendsThin Film Growth
Zone Ia&bZone IcZone TZone IIESZMConclusions
More resultsEnergy fluxDiffusion rateDiffusion lengthConclusions
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
ww
.dra
ft.u
gent
.be
IntroductionTrendsThin Film Growth
Zone Ia&bZone IcZone TZone IIESZMConclusions
More resultsEnergy fluxDiffusion rateDiffusion lengthConclusions
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]
T-S 7 cmT-S 9 cmT-S 11 cmT-S 13 cmT-S 15 cm
intergrain diffusion
recrystallization during grain growth
Transitions Zone Ic/zone T/zone IIw
ww
.dra
ft.u
gent
.be
IntroductionTrendsThin Film Growth
Zone Ia&bZone IcZone TZone IIESZMConclusions
More resultsEnergy fluxDiffusion rateDiffusion lengthConclusions
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]
T-S 7 cmT-S 9 cmT-S 11 cmT-S 13 cmT-S 15 cm
intergrain diffusion
recrystallization during grain growth
Conclusions:
substrate substrate substrate
������� ����������� ���������� ����
substratesubstrate
������� ����
������� ����
����� ������������������� ��������������
� ������ �
���� �����
�����������
����� ������� ��� ��������������
�����������
� ������������
�������������
������� �����
���� ����
� ������������
�������������
������ ����� �
����
Development of microstructure understood if:
-Diffusion rate and length are calculated from energy flux Θ
-In zone T: plasma composition is known
ww
w.d
raft
.uge
nt.b
eIntroductionTrendsThin Film Growth
Zone Ia&bZone IcZone TZone IIESZMConclusions
More resultsEnergy fluxDiffusion rateDiffusion lengthConclusions
International Conference on Thin Films 14
www.ICTF14.ugent.be
17-20 November 2008
‘t Pand, Ghent, Belgium