Ion Beam Analysis of the Composition and Structure of Thin Films
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Transcript of Ion Beam Analysis of the Composition and Structure of Thin Films
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Ion Beam Analysis of the Composition and Structure of Thin Films
Torgny Gustafsson, Physics and
Eric Garfunkel, Chemistry and Chemical Biology
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Experimental Details
Medium Energy Ion Scattering: A refinement of Rutherford Backscattering Spectroscopy with enhanced depth and angle resolution (~3Å vs. ~100Å)
• A quantitative technique, with well known cross sections and an unusually short distance between data and interpretation
• MEIS counts the number of atoms in the sample
• By analyzing peak shapes (energy distributions), depth profiles can be obtained
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MEIS facility at Rutgers*
ion implanter
NRP chamber beam line
XPS system
preparationchamber
scatteringchamber
*Picture taken in 2004
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106
0
105
104
103
102
101
100
10-1
10-2
10-3
10-4
10-5
100 200 400300 500 600 700 800 900
95
151
216
334
629 73084618 15O(p, ) Nα
Energia (keV)
Resonant nuclear reactions
18O 15N p
α
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UHV transfer system for growth and other analysis
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Atomic Layer Deposition
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2D MEIS Data
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122
122 cossin
MM
MMMEE od
•mass (isotope) specific•quantitative (2% accuracy)•depth sensitive (at the sub-nm
scale)
Energy distributions:
77 84 910
500
1000
1500
O(buried)
Zr(buried)
O(surf)
Ge(buried)Si
(surf)
Yie
ldEnergy [keV]
SiO2/ Si /ZrO
2/GeO
x/Ge(001)
Experiment Total Spc
SiO2/poly-Si/ZrO2/Ge(100)
H+ E
nerg
y [k
eV]
Angle115 120 125 130 135 140
H+ Y
ield
Angle [degree]
Energy distribution for one angle
Angular distribution for one element
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Energy spectrum and depth profiles
75 80 85 90 95Energy (keV)
?5
depth
Zr
SiO
Scattered Yield (a.u.)
0 10 20 30 40 50 60 700.0
0.5
1.0
1.5
2.0depth profiles
Si
ZrO2.04
Zr
O
Concentration
Depth (Å)
Simulation of the peaks in the energy spectrum: scattering cross section stopping power (19 eV/Å in ZrO2) energy straggling detector resolution "Near surface" depth resolution 3 Å
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SiO2/Si(001) oxidation (isotope marking)
*Gusev, Lu, Gustafsson, Garfunkel, PRB 52 (1995) 1759.
800 C
900 CTransition zone, SiOx
SiO2
Si (crystalline)
Surface exchange
Growth
T (oC) Time (min) Oxide growth (Å)
High-k
700 30 11
800 30 18
950 30 25
SiO2*
750
165 5
2640 10
900
60 10
300 21
1860 27
• Faster interfacial SiO2 growth in case of high- oxides in comparison to the SiO2 thickness growth for bare Si
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Diffusion in gate dielectrics
SiO2 films:• amorphousamorphous after annealing
• molecular O2 transport in SiO2
• decomposition by SiO desorption
Si-substrate
Atomic oxygen (O) transport in high-high- films filmsSiO2 growth,O-exchange at interface
O-diffusion and exchange in bulk of oxide
High-
O2 decomp.at surface
O2 OSi-substrate
O-exchange in surface layer
SiO2 growthat interface
Oxygen (O2) transport in SiOSiO22
O2
(Many) high- films:• tend to crystallize at low T
• atomic O transport in high- film
• high oxygen mobility
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ZrO2 film re-oxidized in 18O2
No change in Zr profileSurface flat by AFMDeeper O and Si
Isotopic profiling of Zr and Al oxides
Significant interfacial SiO2 growth for ZrO2, less for Al2O3
Dramatic oxygen exchange: 18O replaces 16O SiO2 growth rate faster than DG-like growth
30Å Al2O3 annealed in 3 Torr 18O2
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Presence of nitrogen in high- film: effects on oxygen exchange
100 102 104 106 108
C N
O
Inte
nsity
(a.
u.)
Energy (keV)
as-deposited
NH3/700oC/60s
Sample as grownannealed in
NH3
N content, 1015 cm-2 2.59 4.09
• (HfO2)2(SiO2)/SiN/Si(001) films have been submitted to various post growth anneals (NH3, N2, O2, Tanneal =500-700oC)
• only annealing in NH3/700oC/60s results in nitrogen incorporation in HfSiO6 with oxygen removal (final composition of HfSiO5N (O : N = 5:1))
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Gettering of O in the dielectric by Ti overlayer
• As-deposited amorphous HfO2 film has small amount of interfacial SiO2 (~6-7Å) and excess of oxygen (~HfO2.07)
• Deposited Ti forms uniform layer, no strong intermixing with HfO2;
• Oxygen concentration in Ti layer is small (TiOx, x<0.10)
Si (100)
HfO2.07
SiO2
27Å
6ÅTi
RTSi (100)
HfO2
SiO2
Ti
100 104 108 112 116 120 124 1280
600
1200
1800
2400
Yie
ld
Energy [keV]
as depositedHf
Ti
Si
O
surfint
x10
300oC
UHV
Si (100)
HfOx
HfSiOx
TiOx
15 min UHV anneal 300oC
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Composition of Ti/HfO2/SiO2/Si(001) gate stack (as-deposited)
• Ti layer oxidizes on the surface and at the Ti/HfO2 interface (TiOx, x<1)
• partial depletion of oxygen from HfO2 layer
HfO2 + Ti HfO2-x + VO (HfO2)+ TiOx
• SiO2 remains at the HfO2/Si(001) interface
Si (100)
HfO2
SiO2
TiTiOx
TiO
100 104 108 112 116 120 124 1280
700
1400
2100
Yie
ld
Energy [keV]
ExperimentSimulations
43Å TiO/10Å TiOx/27Å HfO
2/6Å SiO
2/Si(001)
47Å Ti/27Å HfO2/6Å SiO
2/Si(001)
O
Si
Hf
x10 Ti
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Compositional profile after anneal to 300oC
• Ti + xO TiOx
• Decrease of the Si surface peak and decrease of the width of the O peak indicate partial removal of SiO2 layer
• Incorporation of some of the Si initially present in the interfacial SiO2 layer in the high-k layer
• After air exposure Ti oxidation in the surface layer
Si (100)
HfO1.9
HfSiOx
TiOx
100 105 110 115 120 125
Yie
ld [a
.u.]
Energy [keV]
Experiment 52Å TiO
0.5/27Å HfO
1.95/Si(001)
O Si
Hf
x10Ti
x/2 SiO2 + Ti x/2 Si + TiOx
TiOx is Ti alloy overlayerDGo
573K(x=0.49) = -54kJ/mol
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HfO2 deposition on S-passivated InGaAs(001)
104 108 112 116 120 124 128
Yie
ld
Energy [keV]
O
S
Hf
InGa As
x5
Eo=130.5keV
Incident angle = 0o <100>
Scattering angle = 125.3o <111>
• Sulfur (1.3×1015atms/cm2) is distributed at the HfO2/InGaAs interface
• HfO2 layer has small oxygen excess;
• Thin Ga-rich interfacial In0.13Ga0.87Ox:S layer is present,
• Elemental As can still present at the interface at small concentration
0 20 40 600.0
0.5
1.0
Co
mp
osi
tion
Depth [Å]
OC
HfAs
Ga
In
HfO2
InG
aO
x
InGaAs
S
HfO2
5Å InGaOx
InGaAs(001)
S
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Depth profiling for Al/HfO2/S-pass. InGaAs(001)
102 104 106 108112 114 116 118 120 122 124 126 128 130
Sin HfO
2
Yie
ld
Energy [keV]
Eo = 130.5keV
Incident angle = 0o <100>
Scattering angle =125.26o <111>
O
Hf
GaAs
Al
x5
In
135 140 145 150 155 160 165 170 175
S2p
after sputtering
159.5 eV Ga 3S
145 eV As 3p1
140 eV As 3p3
R2M4
R2M3
CP
SBinding Energy (eV)
S
HfO2
a-InGaAsx
InGaAs(001)
135 140 145 150 155 160 165 170 175
164.5 eV S2p
R2M4
R2M3
CP
S
Binding Energy [eV]
S2p
Before Sputter
HfO2
a-InGaAsx
InGaAs(001)
AlOx
XPS results:
S?
HfO2
a-InGaAsx
InGaAs(001)
AlOx
S expected
s
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72 76 80 84 88 92 96
0
100
200
300
400
500
600
Ti
78Å SrTiO3/Si(001)
CO
Sr
Si
Yie
ld
Energy [keV]
Interface compositionNormal incidence, 98keV H+, scattering angle 125o
(substrate Si blocking) SrTiO3/SrTiSixOy/Si(001)
Sr, Ti and O are observed in the interface region - they are visible to the ion beam (not blocked) in this scattering geometry
SrTiO3 78Å
TiSixOy
2Å
Si(001)
6Å
SrO
SrTiO3 78Å
Ti1-xSrxSiyOz
Si(001)
8Å
or