investigation of sio 2/sic interfacial region o and nuclear ...neil/sic_workshop/presentations...sio...
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Universidade Federal do Rio Grande do Sul
Porto Alegre/RS - Brasil
Investigation of SiO2/SiC interfacial region using 18O and nuclear reaction analyses
E. Pitthan, L. D. Lopes, S.A. Corrêa, G. V. Soares, H. I. Boudinov, F. C. Stedile
August 13th, 2015
18O 15Np
α
Nuclear Reaction Analyses18O(p,α)15N
18O(p,α)15N cross-section
Plateau(E ≥730 keV)Total amount
Sharp resonance(E=151 keV)
Profiling
Yiel
d
Simulation
Excitationcurve
Depth 18O
con
cent
ratio
n
Proton energy (keV)
Diff
eren
tial c
ross
sec
tion
(µb/
sr)
Aim:
Oxidation of SiC (and Si) in 18O2 using different oxygenpressures and oxidation times
18O total amount by NR Analysis: 18O(p,α)15N @ 730 keV
18O profile by resonance profiling: 18O(p,α)15N @ 151 keV
E. Pitthan et al. APL Materials 1 (2013) 022101
Influence of oxidation time on flatband voltage and Dit
H. Watanabe et al. , Appl. Phys. Lett. 99 (2011) 021907
SiC
SiO2 xx
Longer oxidation times lead to higher Dit and negative fixed charge
concentration
Influence of oxidation time on flatband voltage and Dit
SiC
SiO2xx x
H. Watanabe et al. , Appl. Phys. Lett. 99 (2011) 021907
Longer oxidation times lead to higher Dit and negative fixed charge
concentration
Influence of oxidation time on flatband voltage and Dit
Longer oxidation times lead to higher Dit and negative fixed charge
concentration
SiC
SiO2
xx x x xxx
H. Watanabe et al. , Appl. Phys. Lett. 99 (2011) 021907
SiC surface after HF etching: ~1×1015 18O/cm2
SiC
S. Corrêa et al. Electrochem. Solid-state Lett. 11 (2008)
Si
Si surface after HF etching: <1×1014 18O/cm2
(SiCx18Oy)
Oxygen remains after etch: Si and SiC
SiCSi18O2
SiSi18O2
Oxygen remains on SiC surface
Longer etching times
Residual 18O after HF etching
18O(p,α)15N @ 730 keV
Residual oxygen on SiC surface is stable upon oxidation time variation
HF etching
E. Pitthan et al. APL Materials 1 (2013) 022101
Si18O2
SiC
Si18O2
SiC
Si18O2
SiC
Oxidation in 18O2:0.5h 1h 10h
SiC SiC SiC
SiO2/SiC Interfacial Region
C. Radtke et al. Appl. Phys. Lett. 85 (2004)
Nuclear Reaction Profiling (NRP)
Depth (nm)
Si18O2
Si
Oxidation in 18O2:
18O22
Si18O2
SiC
Non-abrupt interface in Si18O2/SiC
SiO2/SiC Interfacial RegionNuclear Reaction Profiling (NRP)
E. Pitthan et al. Electrochem. Solid State Lett. 14 (2011)
SiO2/4H-SiC Interfacial region thickness ~ 3 nm for both faces
~ 3nm
Depth (nm)
Si18O2
4H-SiC
Si18O2
Si-face
C-face
~ 3nm
Si-faceC-face
18O(p,α)15N @ 151 keV
151 152 153 154 155Proton beam energy (keV)
Yi
eld
(a.u
.)
Si Face
1100 °C, 1h: 50 mbar 18O2
SiCSi18O2
18O(p,α)15N @ 151 keV
151 152 153 154 155Proton beam energy (keV)
Yi
eld
(a.u
.)
Si Face
1100 °C, 1h: 50, 100 mbar 18O2
SiCSi18O2
18O(p,α)15N @ 151 keV
151 152 153 154 155Proton beam energy (keV)
Yi
eld
(a.u
.)
Si Face
1100 °C, 1h: 50, 100, and 200 mbar 18O2
SiCSi18O2
18O(p,α)15N @ 151 keV
151 152 153 154 155Proton beam energy (keV)
Yi
eld
(a.u
.)
Si Face
1100 °C, 1h: 50, 100 and 200 mbar of 18O2
1100 °C, 100 mbar of 18O2: for 3 h
SiCSi18O2
18O(p,α)15N @ 151 keV
151 152 153 154 155
0 1 2 3 4 5 6 7 8020406080
100
18O
(%)
depth (nm)
Proton beam energy (keV)
Yi
eld
(a.u
.)
Si Face
SiCSi18O2
~ 3nm1100 °C, 1h: 50, 100 and 200 mbar of 18O2
1100 °C, 100 mbar of 18O2: for 3 h
18O(p,α)15N @ 151 keV
150 152 154 156 158 160 162
151 152 153 154 155
0 1 2 3 4 5 6 7 8020406080
100
18O
(%)
depth (nm)
0 4 8 12 16 20 24020406080
100
18O
(%)
Depth (nm)
Proton beam energy (keV)
Yiel
d (a
.u.) Si Face
C Face
1100 °C, 1h: 50, 100, and 200 mbar of 18O2
1100 °C, 100 mbar of 18O2: for 3 h
No significant modifications in the SiO2/SiC interfacial region thickness
assigned to the conditions testedwere observed.
Interfacial region thickness ~ 3 nm
Similar behavior in both faces
Interfacial region after longer oxidation times
4H-SiCSi18O2
100 mbar of 18O2, 1 h, 1100 °C
4H-SiC
Si18O2
100 mbar of 18O2, 10 h, 1100 °C
4H-SiCSi18O2
HF 1%, 23 °C, 290s
~0.1 nm/s
tox
tox
Insignificant modification of the oxide thickness?
Avoid a degradation in depth resolution
150 151 152 153 154 155 156 157Proton beam energy (keV)
Interfacial region in longer oxidation times
Oxidationconditions (1100°C)
Si18O2/4H-SiC interfacial region thickness (nm)
C Face1h, 100 mbar 3.0
10 h, 100 mbar 3.0
Absence of influence of the oxidation parameters on the thickness of the interfacial region
Conclusions
- Presence of a non-abrupt interface in SiO2/SiC (~3nm), regardless offace (Si and C) and oxidation pressure and time.
- Oxygen remains on SiC surface (~1 monolayer) on both faces,independent of oxidation conditions.
-Results suggest that such interfacial properties are not directly related to the interfacial electrical degradation due to long oxidation times.
-While the electrical properties degrade with oxidation time, this is notsimply correlated with interface growth.
Works in Progress at Rutgers/Porto Alegre
SiC nitridation by 15NH3 annealing
Phosphorous incorporation in the SiO2/SiC interfacial region
Investigation of wet oxidation/reoxidation of SiC and SiO2/SiC forboth Si and C faces
Wetting properties of SiC surfaces
Acknowledgements
Prof. Leonard Feldman
Thank you!
[email protected]://www.ufrgs.br/fqsis
EXTRAS
Residual Compounds after oxide removal
4H-SiC
Si face
C face
D D D D D D
after DF+D2O etching~1.0×1015
after DF+D2O etching~0.7×1015
Different properties depending on SiC faceS. Dhar et al. J. Am. Chem. Soc. 9 (2009)
Residual, non-etchable, non-stoichiometric silicon oxide at the interface
Static Pressure Reactor
MOS Capacitors
Origin of negative eff. charge due to thermal oxidation is not yet completely understood
-4 -2 0 2 4 60.0
0.2
0.4
0.6
0.8
1.0
C/C ox
Voltage (V)
SiO2/SiC(negative eff. Charge)
Ideal (theoretical)
SiO2/Si (positive eff. Charge)
Effective charge and channel mobility in SiC MOSFETs
M. Noborio et al.; Phys. Status Solidi A 206 (2009)
Inverse of mobility scales with the negative effective
charge concentration in SiO2 films thermally grown
on SiC
SiC Oxidation:
Ebihara et al. Appl. Phys. Lett. 100 (2012)
- By-products formed in this work would contain 18O. Not distinguished by NRP
- After their interaction with the SiO2 film, the by-products could be incorporated in thesolid phase in all depth regions of the film and be removed by etching, not affectingNRA results.
- Investigate the interaction of CO (SiC oxidation by-product) with SiO2/SiC
)()(2)(223
gsg COSiOOSiC +→←+
)()(2)(2 ssg CSiOOSiC +→←+
SiC oxidation by-productsinteraction with/near SiO2/SiC
Formation of negativecharge observed
Negative charge origin in SiO2/SiC?
CO annealing effects in SiO2/SiC structures:
0 2 4 6 8 101p
10p
100p
1n
10n
-2 0 2 4 60.0
0.2
0.4
0.6
0.8
1.0
Cur
rent
(A)
Voltage (V)
C/C
ox
Voltage (V)
IdealI-V C-V in HF
SiO2/SiC
CO annealing effects in SiO2/SiC structures:
0 2 4 6 8 101p
10p
100p
1n
10n
-2 0 2 4 60.0
0.2
0.4
0.6
0.8
1.0
Cur
rent
(A)
Voltage (V)
C/C
ox
Voltage (V)
IdealI-V C-V in HF
SiO2/SiC
SiO2/SiC + CO annealing (100 mbar, 1000, 1h)
CO annealing effects in SiO2/SiC structures:
0 2 4 6 8 101p
10p
100p
1n
10n
-2 0 2 4 60.0
0.2
0.4
0.6
0.8
1.0
Cur
rent
(A)
Voltage (V)
C/C
ox
Voltage (V)
IdealI-V C-V in HF
SiO2/SiC
SiO2/SiC + CO annealing (100 mbar, 1000, 1h)
SiO2/SiC+ Ar annealing (100 mbar, 1000, 1h)
SiO2/SiC interaction with the oxidation by-product CO is not likely to be responsible for the negative charge formation
C-V Curves in HF
Oxidation Condition Vfb (V) Qeff (×1012 cm-2)100 mbar, 1h 0.9 -2.0200 mbar, 1h 1.4 -3.3100 mbar, 4h 1.9 -2.7
Higher oxidation times and oxygenpressures induce higher negativeeffective charge concentrations.
100 kHz with a 0.25 V/s rate
100 mbar, 1h200 mbar, 1h100 mbar, 4h
0,2 0,4 0,6 0,8 1,0 1,2 1,4
103
104
105
106
107
ângulo de incidência (graus)
Inte
nsid
ade
(con
tage
ns/s
)
O2
X-ray reflectivity (XRR)
2.9 nm
SiO2
6H-SiC (0001)
9 nm
SiO2/SiC
ρ = 2.10 g/cm3
ρ = 2.75 g/cm3
ρ = 3.21 g/cm3
S. A. Corrêa et al. Appl. Phys. Lett. 94 (2009) 251909
Incident angle (°)
Inte
nsity
(cou
nts/
s)w/ interfacial layerw/o interfacial layer
SiO2/6H-SiC Interfacial region thickness ~ 3 nm
O2/NO
SiOxCy
16 nm
1.7 nm6H-SiC (0001)
SiOxNy
XRR
6.5 nm1.2 nm
6H-SiC (0001)
SiOxNy
NO
SiOxCy
ρ = 2.70 g/cm3
ρ = 2.45 g/cm3
2.9 nm
SiO2
6H-SiC (0001)
9 nm
SiOxCy
ρ = 2.10 g/cm3
101
103
105
0,2 0,4 0,6 0,8 1,0 1,2 1,4
102
104
106
Ângulo de incidência (°)
Inte
nsid
ade
(con
tage
ns/s
)
NO
O2/NO
O2
S. A. Corrêa et al. Appl. Phys. Lett. 94 (2009) 251909
Cleaning process:RCA cleaning (t = 10 min,T = 85ºC):•H2SO4/H2O2 (4:1);Removes hydrocarbons from the wafer surface
•NH4OH/H2O2/H2O (1:1:4);Removes organic compounds and metals like Cu, Ag, Ni, Co e Cd
•HCl/H2O2/H2O (1:1:4).Removes alkali ions and hydroxides Fe+3, Al+3 e Mg+2
Removes the native oxide: HF 5%, 1 min
W. KERN; D. A. PUOTINEN. RCA Review, 31 (1970) 187
Static reactor to thermally grow Si18O2
Sampe
Furnace
Quartz tube
Sample Holder
Temperature Control
Zeolite Reservoir
Gas Reservoir
Pressure Measurer
Scroll Pump
Turbomolecular pump
Gate Valve
Pressure Measurer
Inlet
Transfer Rod
A. Koh et al. Appl. Surf. Sci. 174 (2001)
Interfacial Roughness
C. Radtke et al. Appl. Phys. Lett. 85 (2004)
SiO2/SiC Interfacial RegionNuclear Reaction Profiling (NRP)
Depth (nm)
Oxygen vacancies
V. Presser, Cr. Rev. Sol. State, 33, 1 (2008)
C. Radtke et al. Appl. Phys. Lett. 85 (2004)
SiO2/SiC Interfacial RegionNuclear Reaction Profiling (NRP)
Depth (nm)
Understand the effect of this interfacial region on electrical properties
Carbon excessT. Zheleva, Appl. Phys. Lett. 93 (2008)C. Radtke et al. Appl. Phys. Lett. 85 (2004)
SiO2/SiC Interfacial RegionNuclear Reaction Profiling (NRP)
Depth (nm)
I-V Curves
No significan effect of the parameters tested was observed in the Electrical Breakdown Field
AFM
E. Szilágyi et al. J. Appl. Phys. 104, 014903 (2008)
Decrease in the thickness of the SiO2/SiC transitionlayer as the oxide film thickness is increased duringthe initial stages of oxidation can be attributed to asmoothing effect of the interface. Thus, nosignificant modifications in the SiO2/SiC interfacialregion thickness attributable to the conditionstested were observed.
Before etching After etching
150 151 152 153 1540
500
1000
1500
2000
2500
energia dos prótons (keV)
cont
agen
s
0 2 4 6 80
20
40
60
80
100
conc
entra
ção
18O
profundidade (nm)
Demonstração da sensibilidade na determinação de perfis de concentração de 18O por NRP
150 151 152 153 1540
500
1000
1500
2000
2500
cont
agen
s
energia dos prótons (keV)
0 2 4 6 80
20
40
60
80
100
conc
entra
ção
18O
profundidade (nm)
Demonstração da sensibilidade na determinação de perfis de concentração de 18O por NRP
221815 226.0/.10 SiOdenmcmOat =
ρSiO2 = 2.21 g/cm3 MM SiO2 = 60 g/mol
1 cm3 of SiO2 = 2.21 g/cm3 de SiO2 = x of O atoms
60 g = 2 x 6.02E23 of O atoms
x = 4.43E22 of O atoms/cm3
1x10-2 m de SiO2 = 4.43E22 of O atoms/cm2
1x10-2 m de SiO2 = 4.43E7 x 1015 of O atoms/cm2
0.226 nm de SiO2 = 1015 of O atoms/cm2