Post on 13-Sep-2018
Thin Film Materials and Coatings Winter Semester 2016/17
Dr. Gunther Richter
Raum 5Q-R11, Tel: 3587
Outline:
1. Basics: Crystallography, Surface Energy, Wulff Shape
2. Vacuum
3. Growth Theories and Models
4. Thin Film Analysis Techniques
5. Physical Vapor Deposition
6. Chemical Vapor Deposition
7. Microstructure Tailoring in Thin film and Nanostructures
Motivation – Thin Film Effect in metallic Films
0,00 0,05 0,10
0,00
0,01
0,02
0,03
0,04
1
23456
7
A
B
C
D
E
F G
a
b
c
de
f
g
Bulge-Testing
Cu/Si Vinci (WC)
Cu/Si Thouless (WC)
Cu/Si Flinn (WC)
Cu/Si Weiss (WC)A Cu/Ag/Si Schmidt (WC)a Cu/Ta/Si Schmidt (WC)
AlxOy/Cu/Si Wiederhirn (WC)
Si3N4/Cu/Si Vinci (WC)
Si3N4/Cu/Si Keller (WC)
SiNx/Cu/Si Shu (WC)
Ti/Cu/Si Xiang (WC)
SiOx/Cu/Si Shen (WC)
1% Al/Cu/Si Weiss (WC)
-Fe/Al2O
3 epi (WC in UHV)
Ag/Si Kobrinsky (WC)
SiOx/Ag/Si Kobrinsky (WC)
Al/Al2O3 epi Dehm (WC)
Al/Si Dehm (WC)
Al/Si Venkatraman (WC)
Al/Si Doerner (WC)
Au/Si Sauter (WC)
Au/W/Si Sauter (WC)
Au/Si Leung (WC)
Si3N4/Au/Si Leung (WC)
Cu/Al2O3 epi Edongue (WC)
Cu/Si Balk (WC)
Cu/Si Keller (WC)
Al/Si Korhonen (X)
Al/Si Paszkiet (X)
SiNx/Al/Si Paszkiet (X)
Au/polyimide single Gruber (X)
Au/polyimide Gruber (X)1 Cu/polyimide Hommel (X)
Cu/Ta/polyimide Gruber (X)
Ta/Cu/Ta/polyimide Gruber (X)
Nix model for Al/Si
von Blanckenhagen model for Al
Nix model for Cu/Si
Nix model for Cu/polyimide
von Blanckenhagen model for Cu
Cu Onuseit (B)
20 nm1000 nm
Wafer curvature
Models
No
rma
lize
d R
T flo
w s
tre
ss
/G
[ ]
1/h [nm-1]
Stress [MPa]
X-Ray
fcc metals
Fe/Al2O
3
Scaling of flow stress with inverse film thickness
Beispiel: Korrelation Mikrostruktur - mechanische Eigenschaften
polycrystalline Cu
10 µm
600nm Cu on (0001) -Al2O3
polycrystalline
epitaxial
-100
0
100
200
300
400
0 100 200 300 400 500
flow
str
ess
[MP
a]
temperature [°C]
epitaxial Cu
50 µm
Mikrostruktureffekt auf die thermischen Fließspannung dünner Cu Schichten
Motivation
• Electronic Materials
• Magnetoelectronics (Tunneling magnetoresistance)
• HT Superconductors
• Thermal Barrier Coatings
2 cm
200 nm
20 Å
ZrO2
Al2O3
Flugzeugturbine
Turbinenschaufel
Gefüge der Wärmedämmschicht
Atomare Struktur
Thin Films: “Examples”
microchip
IBM
micromirrors
Lucent 10 µm 100 µm
Motivation – Thin Film Effect in metallic Films
0,00 0,05 0,10
0,00
0,01
0,02
0,03
0,04
1
23456
7
A
B
C
D
E
F G
a
b
c
de
f
g
Bulge-Testing
Cu/Si Vinci (WC)
Cu/Si Thouless (WC)
Cu/Si Flinn (WC)
Cu/Si Weiss (WC)A Cu/Ag/Si Schmidt (WC)a Cu/Ta/Si Schmidt (WC)
AlxOy/Cu/Si Wiederhirn (WC)
Si3N4/Cu/Si Vinci (WC)
Si3N4/Cu/Si Keller (WC)
SiNx/Cu/Si Shu (WC)
Ti/Cu/Si Xiang (WC)
SiOx/Cu/Si Shen (WC)
1% Al/Cu/Si Weiss (WC)
-Fe/Al2O
3 epi (WC in UHV)
Ag/Si Kobrinsky (WC)
SiOx/Ag/Si Kobrinsky (WC)
Al/Al2O3 epi Dehm (WC)
Al/Si Dehm (WC)
Al/Si Venkatraman (WC)
Al/Si Doerner (WC)
Au/Si Sauter (WC)
Au/W/Si Sauter (WC)
Au/Si Leung (WC)
Si3N4/Au/Si Leung (WC)
Cu/Al2O3 epi Edongue (WC)
Cu/Si Balk (WC)
Cu/Si Keller (WC)
Al/Si Korhonen (X)
Al/Si Paszkiet (X)
SiNx/Al/Si Paszkiet (X)
Au/polyimide single Gruber (X)
Au/polyimide Gruber (X)1 Cu/polyimide Hommel (X)
Cu/Ta/polyimide Gruber (X)
Ta/Cu/Ta/polyimide Gruber (X)
Nix model for Al/Si
von Blanckenhagen model for Al
Nix model for Cu/Si
Nix model for Cu/polyimide
von Blanckenhagen model for Cu
Cu Onuseit (B)
20 nm1000 nm
Wafer curvature
Models
No
rma
lize
d R
T flo
w s
tre
ss
/G
[ ]
1/h [nm-1]
Stress [MPa]
X-Ray
fcc metals
Fe/Al2O
3
Scaling of flow stress with inverse film thickness Scaling of flow stress with inverse film thickness ??
1µm
40°
substrate
Epitaxial, single crystalline multilayers
Tobias Schmidt, Department Arzt
Ag/Ni/Si(100) Multilayers
Influence of microstructure on
mechanical properties:
Polycrystal single crystal
Bulk thin film
FIB
Composite materials
Cornelia Schurr, Department Arzt
Cu/CNT/Cu/Si
Carbon nano tubes display extraordinary properties
Fabrication of composites with defined
microstructure and composition
FIB
2.2 Wachstumsmodi: Inselwachstum
100 nm
35 nm Pt (Inseln) auf (100)SrTiO3: Inselwachstum, Koaleszenz, Keimbildung
TEM Hellfeldaufnahme AFM Aufnahme (Bildgröße 1 mm x 1mm)
Polli (2000)
N. Yun Jin-Phillipp , Department Dosch
Nano particles
polycrystalline
film
epitaxial
layer
R
1/T
Rh/-Al2O3(0001)
• island density: f(TS, R)
• oxidization is function of island facetts
well defined growth conditions required
HRTEM
Island Layer
Max-Planck-Institut für Metallforschung; ZWE Dünnschichtlabor
Pr:Einbau - Au_4f
Arb
itra
ry U
nit
s
100 98 96 94 92 90 88 86 84 82 80
Binding Energy (eV)
DE= 1.0 eV
Mg-k XPS Si 2p
Au 4f7/2 Au 4f5/2
as derived
650°C
700°C
750°C
800°C
Au/SiOx/Si Surfaces
• Au and Si form eutectica (chemical shift)
• evaporation of eutectica at T > 750°C
Nano structuring of surface
Surface reactions
Beri Mbenkum, Department Spatz
Structuring
Beri Mbenkum, Department Spatz
AFM
arteficial nanostructures
• Fabrication process: bottom-up/condensation by PVD
• Crystal morphology: needle / prismatic, diameter 20 -200 nm, Length < 300 µm
1.1 Kristallographie
Das Kristallgitter
7 Kristallsysteme
Aufgrund der Symmetrie von Kristallen gibt es 14
Bravais-Gitter, die zur Beschreibung aller
Kristallstrukturen ausreichen. Die Bravais-Gitter
verteilen sich auf 7 Kristallsysteme. So besteht z.B. das
NaCl Gitters aus 2 kubisch flächenzentrierten
Translationsgittern (eines für Na, eines für Cl), die um
½ ½ ½ gegeneinander verschoben sind.
Gittertypen und Achsensysteme
Bravais-lattice
System Primitivität Benennung Achsen/Winkelbedingunge
n
kubisch 1.) einfach-primitv
2.) zweifach-primitv
3.) vierfach-primitv
eckenbesetzt
raumzentriert
allseitig flächenzentriert
a = b = c, = b = g = 90°
tetragonal 4.) einfach-primitv
5.) zweifach-primitv
eckenbesetzt
raumzentriert a = b c, = b = g = 90°
hexagonal 6.) einfach-primitv
7.) dreifach-primitv
7'.) einfach-primitv
eckenbesetzt
2-fach raumzentriert
rhomboeder-eckenbesetzt
a = b /= c, = 120°, g = 90°
rhombisch
8.) einfach-primitv
9.) zweifach-primitv
10.a) zweifach-primitv
10.b) zweifach-primitv
10.c) zweifach-primitv
11.) vierfach-primitv
eckenbesetzt
raumzentriert
(vorder-) flächenzentriert
(seiten-) flächenzentriert
basiszentriert
allseitig flächenzentriert
a b c, = b = g = 90°
(rhomboedrisch) o. Abb. a = b = c, = b = g 90°
monoklin 12.) einfach-primitv
13.) zweifach-primitv
eckenbesetzt
basiszentriert a b c, = g = 90° b
triklin 14.) einfach-primitv eckenbesetzt a b c, b g 90°
Lattice distances
Angle between planes
Stereographic projection
Wulff Net
Winkel zwischen Kristallebenen
Winkel
Surface crystallography
fünf Bravais-Netze zur Beschreibung der
Oberflächengeometrie mit Einheitsvektoren
as und bs
Translation T = m·as + n · bs
Surface tension/stress/energy
Surface energy
Surface energy
Stereographic Projection/Surface
energy
Wulff Shape
Wulff Shape
Wulff Shape
Max-Planck-Institut für Metallforschung
A.D. Polli SrTiO3
Pt
Wulff plot
gF = r{hkl}
Minimize surface energy with
constant volume
Equilibrium shape
Wulff plot
Growth Theory: simple thermodynamic theory
Free energy change DG
radius r*
SIFFV rararaGraG ggg 2
2
2
2
2
1
3
3 DD
gS: Substrate surface energy ai: geometrical factors
gF: Film surface energy
gIF: Interface energy
layer by layer growth
(Frank van den Merwe, FM)
Film Growth Modes
FIFS ggg FIFS ggg
island growth
(Volmer-Weber, VM)
layer plus island growth
(Stransky-Krasanov, SK)
Complete wetting partial wetting
f
Surf
ace e
nerg
y r
atio
M. Ohring,
Materials Science of
Thin Films, 2002
Layer growth can only tolerate small
amounts of misfit (strain energy)
→ strain relaxation by Stransky-Krastanov Growth
Stability Regions of Growth Modes
Winterbottom
Winterbottom II
Winterbottom III
1
2
r
rFSIF ggg
Winterbottom IV
Gas theory
Vacuum
Vacuum
Vacuum
Charakteristische Größen des Vakuums:
Das Vakuum muss ausreichend sein, damit sich die Probe
während der Messung nicht verändert!
Annahme: Im Vakuum gelten die Gleichungen für das freie Gas:
N: Zahl der Atome
im Volumen V
T: Temperatur
kB: Boltzmann-Konstante
Auftreffrate von Restgasatomen auf der Probe:
m: Masse der Gasatome
Faustregel:
TkV
Np B
mT
pb
Tkm
pr
B
2
12/11224 PaKsm Moleküle1063.2 b12/11226 mbarKsm Moleküle1063.2 b
Freie Weglänge der Restgasmoleküle:
22
p
TkB
Herleitung aus der kinetischen Gastheorie:
: „Durchmesser der Restgasmoleküle
Pumpentyp Druckbereich (Pa)
mech. Drehschieberpumpe Atmosphärendruck - ca. 10-1 Pa
Sorptionspumpe Atmosphärendruck - ca. 10-3 Pa
Öldiffusionspumpe 1 Pa - 10-7 Pa
Turbomolekularpumpe 1 Pa - 10-9 Pa
Kryopumpe 10-1 Pa - 10-9 Pa
Ti-Sublimationspumpe 10 Pa - 10-9 Pa
Ionengetterpumpe 10-3 Pa - 10-9 Pa
Zeit zur Bildung einer Monolage Adsorbat:
Abschätzung: in der Kammer herrscht ein Druck von 1·10-6 mbar
r 3·1014/(cm2s) N2 Moleküle bei Raumtemperatur
1 ML = 1015 Atome/cm2 1 ML adsorbiert alle 3 s
Vakuumerzeugung durch Pumpen:
- Reihenschaltung mehrerer Pumpen
- Pumpwirkung durch Kompression, Diffusion, Gettermaterialien oder Kondensation
- Pumpgeschwindigkeit hängt vom Pumpentyp und dem zu pumpenden Gas ab
Übersicht Vakuumpumpen
Drehschieberpumpe
Diffusionspumpe
Ionengetterpumpe
Turbomolekularpumpe
Übersicht Vakuumpumpen
Vapor pressure
Vapor pressure
Evaporation
Evaporation
Film Thickness
Film Overgrowth
Nucleation barrier
Film nucleation
Film nucleation
Film nucleation
Film nucleation
Film nucleation
Coalescence
Adatom density
Ehrlich-Schwoebel-barrier
Microstructure
Critical cluster size
Film nucleation
Film nucleation
Film nucleation
Defect/trap energy
Nucleation Ag/W(110)
Energy values
Influence of T
Energy values II
Critical nuclei size
Step decoration
Step decoration
Stages of film growth
Coalescence
Nucleation and Growth
22 nm Pt 200 nm Pt
Pt on (100) STO (850°C) (AFM-images) (A.D.Polli)
Images: 10 mm 10 mm
Quantification
(island size distribution, number of islands)
• Number of atoms in a critical nucleus i
• Nucleation energy Ei
• Activation energy for adsorption Ea
• Activation energy for diffusion Ed
• Binding energy Adatom - Defect
Parameters: i, Ei, Ed, Ea
Fundamental processes
e.g. J. A. Venables, Introduction to Surfaces and Thin Films, Cambridge University Press 2000
thickening
Surface preparation: SrTiO3(001)
3 mm
Surface preparation: SrTiO3(001)
2 mm
200 eV, 10 min ion etching Annealing 1 h, 800°C
Pd/SrTiO3(001): STM
Tailoring the microstructure
0.0010 0.0015 0.0020 0.0025 0.0030 0.0035
-5.5
-5.0
-4.5
-4.0
-3.5
-3.0
-2.5 (001) - Körner
(001) + (111) - Körner
(111) - Körner
ln(R
) (ln
(nm
/s))
1/T (K-1)
(001) grains
(001) + (111) grains
(111) grains
- Island growth: temperature independent
- Orientation is function of temperature 30 nm
STM
45 nm Pd <60°C
RHEED
{111}Pd || (001)SrTiO3
50 nm
STM
RHEED
(001)Pd || (001)SrTiO3
[100]Pd || [100]SrTiO3
0,00 0,05 0,10 0,15 0,20 0,25 0,30 0,35
4,0x1015
6,0x1015
8,0x1015
1,0x1016
1,2x1016
1,4x1016
TSub
= 600°C
R = 0.0010 nm/s
R = 0.0049 nm/s
R = 0.0083 nm/s
Isla
nd D
ensity
(m-2)
Film Thickness (nm)
Approximaton of Rate Theory:
ia.u.K.
= 0.85 ± 0.18
iv.K.
= 1.26 ± 0.40
iN i = 1
Ei = 0
p = 0,34 ± 0,07
10-3
10-2
4x1015
6x1015
8x1015
1016
1,2x1016
1,4x1016
log
(nx)
(m-2)
log(Rate) (nm/s)
p(i) = nx (R ) @ TS = constant
Experiment: Rate Dependence
S
Act
0
x
kT
Eexp
D
Rn
pR EAct
p
Ts x
0,0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,810
15
1016
R = 0.0049 nm/s
TS = 500°C
TS = 600°C
TS = 700°C
Isla
nd D
ensity
(m-2)
Film Thickness (nm)
0.00100 0.00105 0.00110 0.00115 0.00120 0.00125 0.00130
35.5
36.0
36.5
37.0
37.5
38.0
EAkt
= (0,63 ± 0,04) eV
ln(n
x)
1/T (K-1)
EAct
= nx(T
S) @ R = constant
S
Act
0
x
kT
Eexp
D
Rn
pR EAct
p
Ts x
Activation Energy Determination
1,00 1,05 1,10 1,15 1,20 1,25 1,30
0,0
5,0x10 -4
1,0x10 -3
1,5x10 -3
2,0x10 -3
2,5x10 -3
Data für R = 0.0049 nm/s 2D-projektion of fit
n x /N
0
1/T (1000/K)
satu
ration isla
nd d
ensity
S
d00x
2/7
0
x
S
a
2/5
0
x1
kT
Eexp
ND
N
n
kT
Eexp
N
nK
Ea = (1.69 ± 0.05) eV ; Ed = (0.64 ± 0.20) eV ; i = 1
Pd/SrTiO3(001): Nucleation
Grain growth and texture
Epitaxial island growth - all island have same crystallographic orientation
- growth of isalnds with minimal interface and surface energy
Polycrystalline layer - Many isalnds with different crystallographic orientation
- Coalescence grain boundaries
- Grain zize is dependand on island nucleation rate I
and island growth rate G
Grain growth and texture
Texture - favoured orientaion between islands/grains relative to the substrate
- Non random orientation
- Fibre texture: d und b constant, random
Grain size
Grain size in polycrystalline thin films:
Simple case:
1. Constant nucleation rate
2. Constant growth rate on surface
Development of Johnson-Mehl structure
d: average grain size
scmI
2
#
s
cmG
3/1
491.1
I
Gd
Reality quite often much more complicated,
but there is a general trend:
Increasing G/I grain size d increases!
Reminder nucleation
How many nuclei form?
(Ohring (1992))
Increase of supersaturation K or
Deposition rate R I increases
Growth velocity?
(z.B. Ohring (1992))
Icrease of substrate temperature T
Growth rate of nucleus G increases
2.4 nucleation and growth
Nucleation and growth (z.B. Ohring (1992))
Increasing G/I grain size d increases
kT
Q*GexpR~
I
G SDn D1
For n > 1 : increasing deposition rate R
Grain size d decreases!
Often seen trend: grain size d increases with
substrate temperature T .
(DG* < QSD)
Exponent n (≈2): dependand on deposition rate
R: deposition rate
DG*: critical nucleation energy (nucleaus with radius r*)
QSD: activation energy for surface diffusion
TEM Hellfeldaufnahme (Querschnitt)
von Pt Inseln auf SrTiO3
Polli (2000)
Grain growth
Normal grain growth Grain boundary migration: lowering total system energy by lowering interface/grain boundary energy
Big grains grow
Small grains shrink
Aberage grain size increases
Growth rate = mobility driving force
driving force: (Energy/Volume)
gbg
r
Grain growth
rm
dt
rdv
gbg
grain growth rate, v
kT
Qmm
gbexp0
Qgb = activation of grain boundary diffusion
r
0r
= average grain boundary energy
= average grain radius
m = average grain boundary mobility
= average starting grain radius
gbg
= curvature
rkT
Q
dt
dr gbgb g
exp~
tkT
Qrr
gb
exp~2
0
2
Grain growth
Driving forece:
Grain boundary energy
Simulation: normal grain growth (Frost (1988))
Stagnation:
Grain boundary grooves
(Mullins (1958)) Microstructure of thin films - average grain size roughly 2 film thickness
r ≈ h (Mullins (1958))
- grain size distribution is log-normal distribution
Frost (1990), Palmer (1987), Gottstein (1999)
Normal grain growth
Grain microstructure in interconnects (Simulation and experiment)
Knowlton (1995)
Normal grain growth in interconnects:
Bamboo structure, gain boundaries „perpendicular“ to interconnect axis
TEM Aufnahme einer Al-Schichten (1% Cu)
Walton (1992)
Abnormal grain growth
Abnormal grain growth: Normal grain growth: stagnation by grain boundary grooves
Additional grain growth abnormal grain growth!
Result: d >> h
Abnormal grain growth
Abnormal grain growth in Ge
(Palmer (1997))
(( h = 30 nm, annealed 1 h @ 900°C)
Growth of (111) grains
Abnormal grain growth in Pd
(Wagner (2001))
( h = 35 nm, annealed 5 min @ 600°C)
Single crystalline (100) thin layer (epitaxial grain growth)
Aufgedampft
und
ausgelagert
Aufgedampft
TEM Hellfeldaufnahme
TEM Hellfeldaufnahme (Querschnitt)
Abnormal Grain Growth
gPd
(111), gPd
(001): A.M. Rodríguez, G. Bozzolo, and J. Ferrante, Surf. Sci. 289 (1993) S.100
SrTiO3
Pd
polykristalline Keime
SrTiO3
Pd
epitaktische Keime
SrTiO3
Pd
polykristalliner Film
SrTiO3
Pd
epitaktischer Film
epitaktische Keime
epitaktische Inseln
Inselwachstum
TSub
=
250°C
<60°C
<60°C
600°C
TSub
=
> 250°C
> 250°C
> 250°C
> 250°C
Glue
Glue epitaxial film epitaxial islands
polycrystalline film
island growth
epitaxial nucleii epitaxial nucleii
polycrystalline nucleii
DF- CTEM
DF- CTEM
gtot(111) = gIF
(111) + gSF(111) > gtot
(001) = gIF(001) + gSF
(001)
gIF(001) = 1.0 Jm-2, gSF
(111) = 1.7 Jm-2, gSF(001) = 2.2 Jm-2
gIF(111) > 1.5 Jm-2
Driving force for abnormal grain growth
Abnormal grain growth
Tfs D
gb
avmin MMW
g
2
gb
i
gb
si/s
hhW
g
gD
g
gD
Strain energy W Surface and interface energy Ws/i
min,iav,ii
min,sav,ss
gggD
gggD
avminfs
is
MMhT
gDgDD
2
2 1
depgg TTT D
W = Ws/i
=> Balance between W - und Ws/i determines texture
Abnormal grain growth
Texture diagram Phasen boundary between (111) and (100) texture
(fcc metals)
Thompson (1995)
DT 2 ~ 1/h
100111
100111
MM
,s,s
gg Result: DT = constant there is a critical thickness hcrit
texture is determined by strain energy
hcrit