www.phi.com angle dependent xps 1 sca lab 6 scanning electron source al anode 5-axis sample stage...
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Angle Dependent XPS
1
M
SCA LaB6 Scanning Electron Source
Al Anode
5-Axis Sample Stage
• Electrons
• Photoelectrons
• X-rays
Multi
Chan
nel
Detec
tor
Scanning Input Lens
A
EllipsoidalMonochromator
The analysis depth is varied by changing the sample tilt angle
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Angle Dependent XPS
2
q = 90° q = 10°q
q
d = l sin qd = analysis depth l = electron mean free path q = photoelectron take off angle
dd
X-ray BeamX-ray Beam
AnalyzerInput Lens
AnalyzerInput Lens
e - e -
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ADXPS Profile of theNative Oxide on a Si Wafer Surface
3
280285
2902950
2
4
60
500
1000
1500
Binding Energy (eV)c/
s
C 1s
525530
5355400
2
4
60
5
10
15
Binding Energy (eV)
c/s
O 1sx103
95100
1051100
2
4
60
5
10
Binding Energy (eV)
c/s
Si 2pmetal
oxide
x103
Corrected for Take-Off-Angle intensity variation
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 15
10
15
20
25
30
35
40
45
50
55
Sine of the Photoelectron Take-off Angle
Ato
mic
Con
cent
ratio
n (%
)
O 1s
C 1s
Si 2p - metal
Si 2p - oxide
Chemical Composition Atomic Concentration Profile
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ADXPS Profile of theNative Oxide on a Si Wafer Surface
4
929496981001021041061081101120
500
1000
1500
2000
2500
3000
3500
4000
Binding Energy (eV)
c/s
Pos. Chem. State 99.51 Si 2p3 metal100.11 Si 2p1 metal103.36 Si 2p oxide
Si 2p
Curve Fitting Used to Isolate Si Metal and OxideChemical Composition Atomic Concentration Profile
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 15
10
15
20
25
30
35
40
45
50
55
sine [toa]
Ato
mic
Con
cent
ratio
n (%
)
O 1s
C 1s
Si 2p - metal
Si 2p - oxide
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Interpretation of ADXPS ProfilesUsing a Stratification Algorithm
The stratification algorithm requires peak intensity data
from two or more take off angles. The minimum data set
should include a high and low take off angle.
Estimation of layer order– The peak intensity ratios of all peaks are compared between all
the measured take off angles. The number of layers and layer
order is based on the correlation of peak intensity ratios.
Estimation of film thickness and composition– The peak intensities measured at the high take off angle and
the layer order information are used to calculate layer thickness
and composition.
– The algorithm is useful for qualitative sample to sample
comparisons
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Assumptions and Limitations of theStratification Algorithm
Stratification model assumptions– Individual layers are continuous and uniform in thickness
– Individual layers are uniform in composition
– Interfaces are abrupt
Stratification model limitations– Generic electron mean free paths are applied for thickness
calculations• Since the model is not calibrated for the sample being
measured, the absolute layer thicknesses may contain
systematic error
– If the actual sample composition violates any of the
assumptions, this will impact the layer detection process,
composition, and thickness results
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Stratification Algorithm Interpretation of theADXPS Profile of the Native Oxide on a Si Wafer
7
Structure Analysis with automatic layer assignment
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 15
10
15
20
25
30
35
40
45
50
55
sine [toa]
Ato
mic
Con
cent
ratio
n (%
)
O 1s
C 1s
Si 2p - metal
Si 2p - oxide
Chemical Composition Atomic Concentration Profile
Structure Description
-2.5
-2
-1.5
-1
-0.5
0
D
epth
(nm
)
C 1s (100.0 %)
O 1s (67.0 %) Si 2p – oxide (33.0 %)
Si2p – metal (100.0 %) Layer1
Layer2(2.03 nm)
Residue (1.77e-008)
Top Layer(0.19 nm)
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ADXPS Profile of a Self AssembledThiol Monolayer on Au
8
808590950
50
0.5
1
1.5
2
x 105
Binding Energy (eV)
c/s
Au4f
5255305355400
50
2000
4000
6000
Binding Energy (eV)
c/s
O1s
2802852902950
50
5000
10000
Binding Energy (eV)
c/s
C1s
1551601651700
50
500
1000
1500
Binding Energy (eV)
c/s
S2p
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10
10
20
30
40
50
60
sine [toa]
Ato
mic
Con
cent
ratio
n (%
)
S 2p
O1s
Au 4f
C 1s (C-C/C-H)
C 1s (C-O)
Chemical Composition Atomic Concentration Profile
Sample in courtesy of Dr. Sophie NoelLaboratoire de Génie Electrique de ParisURA CNRS Universités Paris
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ADXPS Profile of a Self AssembledThiol Monolayer on Au
9
2782802822842862882902922942962981
1.1
1.2
1.3
1.4
1.5
1.6
1.7x 104
Binding Energy (eV)
c/s
Pos. Sep. %Area284.82 0.00 84.38 C-C/C-H286.88 2.06 15.62 C-O
C 1s
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10
10
20
30
40
50
60
sine [toa]
Ato
mic
Con
cent
ratio
n (%
)
S 2p
O1s
Au 4f
C 1s (C-C/C-H)
C 1s (C-O)
Chemical Composition Atomic Concentration Profile Peak Fit Routine Separating C 1s Chemical States
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ADXPS Profile of a Self AssembledThiol Monolayer on Au
10
Structure Description
-2.5
-2
-1.5
-1
-0.5
0
Dep
th (
nm)
O 1s (41.3 %)
C 1s C-O (58.7 %)
C 1s C-C/C-H (100.0 %)
S 2p (100.0 %)
Au 4f (100.0 %) Layer1
Layer2(0.11 nm)
Layer3(1.58 nm)
Top Layer(0.31 nm)
Residue (1.18e-010)
0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 10
10
20
30
40
50
60
sine [toa]
Ato
mic
Con
cent
ratio
n (%
)
S 2p
O1s
Au 4f
C 1s (C-C/C-H)
C 1s (C-O)
Chemical Composition Atomic Concentration ProfileStructure Analysis with automatic layer assignment
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HfO2 on Si
0.4 0.5 0.6 0.7 0.8 0.9 10
20
40
60
80
100ADXPS Profile
sine [toa]
Ato
mic
Con
cent
ratio
n (%
)
O 1s
C 1s
Hf 4f
Si 2p (oxide)Si 2p (metal)
141822263020°
30°
45°
75°
0
0.5
1
1.5
2
2.5x 104
Binding Energy (eV)
c/s
Hf 4f
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HfO2 on Si
1 2-4.5
-4
-3.5
-3
-2.5
-2
-1.5
-1
-0.5
0Structure Analysis
Dep
th (
nm)
1.11 nm O 1s 71.2% Hf 4f 28.8%
2.96 nm O 1s 65.2% Si 2p 13.8% Hf 4f 21.0%
Si 2p 100%
This model was created by a stratification analysis tool in MultiPak. Generic attenuation lengths were used.