nuclear reaction analysis and narrow profiling
TRANSCRIPT
Topics
Introduction to Si and SiC Principles of Isotopic Tracing Principles of Nuclear Reaction Analyses:
NRA and NRP Results on thermal oxidations of Si and SiC
Advantages of Si
Oxide film thermally grown (SiO2)Excelent electrical and thermodinamic
characteristics SiO2/Si interface
Low density of electrically active states
Silicon: the most widely usedsemicondutor in the
microelectronic industryPerformanceVolume (cm3)
MOSFETGate Electrode
Source
Gate oxide
Drain
Dielectric/semicondutor interface(inversion layer)
V+-
V+-
From chip to transistor - Intel
18O2
D218O
Natural oxygen: 99,759% 16O 0,204% 18O 0,037% 17O
18O2 97% ~U$ 1,000/L D218O ~US$ 2,000/mL
Natural hydrogen: 99,985% 1H 0,015% 2H = D
Static atmosphere reactor
Using isotopes and nuclear reactions to understand theatomic transport during the Si thermal oxidation
SiSiO2
Si
O2
(T = ~ 1000 °C)
Oxidation in O2 (natural abundance):
Isotopic Tracing
SiO2
Si
Oxidation in 18O2
18O2
Who is the mobile species ? O, Si, or both ?
SiO2
Si
18O2
Si is the mobile species
SiO2
Si
Si18O2
Mobile species during oxidation
1st possibility:
SiO2
Si
18O2
O is the mobile species
SiO2
SiSi18O2
Mobile species during oxidation
2nd possibility:
Appl.Surf. Sci.39 (1989) 65
18O 15Np
Nuclear Reactions
POW !
NRP NRA
0 100 200 300 400 5000
500
1000
1500 18O(p, ) 15N
Channel
Ion ImplantationLaboratory
UFRGS
HVEE 3 MV Tandetron
NRA and RBS chamber
HVEE 500 kV single-ended: NRP chamber
Resonant Nuclear Reaction - NRP
ER
ER
ER
E (>E )2 1
E1
Sample
0 100 200 300 400 5000
500
1000
1500 18O(p, ) 15N
Channel
Profile
Proton Energy
Yiel
dExcitation Curve
Depth [L]
Con
cent
ratio
n
yes
no
Recordvalues
Increaseenergy
Totalcharge?
Reset countersStart count ing
16O2 -18O2 @ 1000oC
150 152 154 156 158 160 162
Experimental Simulated
Cou
nts
(a.u
.)
Proton energy (keV) 0 5 10 15 20 25 30 35 40 450
20
40
60
80
100
Con
cent
ratio
n 18
O (%
)
Depth (nm)
Oxygen is the mobile species and it is transported:- By diffusion, interacting with network defects (surface region)- Interstitially, without reacting with the oxide already formed,until reaching the semiconductor interface and there reactingforming SiO2
Profiles reliability16O2 -18O2 @ 1000oC
16O2 -18O2 @ 1000oC
Trimaille et al. The Physics and Chemistry of SiO2 and the Si-SiO2 Interface - 3, ed. H.Z. Massoud et al. (The Electrochemical Society, Pennington, 1996), vol.96-1, p. 59
NRA: D amounts• Nuclear reaction D(3He,p)4He: plateau ~ 700 keV• Total amounts of D (insensitive to H)
D. Dieumegard et al.NIM 166 (1979) 431
0 100 200 300 400 5000
50
100
150
200
D(3He,p)4He
Channel
coun
ts
D quantification
sensitivity ~ 4.0 x 1012 D.cm-2
Accuracy: 10%
3He+ (< 700 keV)
D(3He,p)4He at 700 keV
Areal density of 16Oin oxide films versus time of chemical dissolution in dilute HF-solution
Areal densities of deuterium in oxide films versus time of chemical etching. The corresponding D profiles determined by differentiation are shown in the insets: (a) as-loaded with D2; (b) loaded with D2 and annealed in vacuum at 650oC for 30 min
Silicon
thermalSiO2
D D
I.J.R. Baumvol, E.P. Gusev, F.C. Stedile, F.L. Freire, Jr., M.L. Green, D. Brasen, Appl. Phys. Lett. 72 (1998) 450.
I.J.R. Baumvol, F.C. Stedile, C. Radtke, F.L. Freire, Jr., E.P. Gusev,M.L. Green, D. Brasen, Nucl. Instrum. Meth. B 204
D profiling
MotivationSiC
High temperatureElectronics and sensors
High frequencypower devices
Low and medium voltagehigh switching frequencypower electronic devices withlow losses
Bandgap Saturationdrift velocity
Thermalconductivity
Mobility Breakdownel. field*
* for 1200 V blocking voltage
Silicon
Siliconcarbide
Japan: 1% less energy loss
Energy save ~ 4 nuclear power plants
SiC < energy loss than Si
Si bipolar transistor SiC MOSFET 85% less energy loss
Carbon
b
c
a
Silicon 6H-SiC Si-face (0001)
6H-SiC C-face (0001)
SiC : only compound semiconductor onwhich it is possible to thermally grow a
SiO2 film, as on Si
Part of SiO2/Si technology can betransfered or adapted to the SiO2/SiC
technology
Interfaces: SiO2/Si x SiO2/SiC
K.C. Chang et al. Appl. Phys. Lett. 77 (2000) 2186http://www.ibm.com
C
Si
SiCSi-face
Single step in18O2
151 153 155 157
0 10 200
50
100
18 O
(%)
Depth (nm)
Alph
a Yi
eld
(a.u
.)
Beam Energy (keV)
SiO2 /SiC /Si
C. Radtke, I.J.R. Baumvol, B.C.Ferrera, F.C. StedileAppl. Phys.Lett. 85 (2004) 3402
oxidation in 16O2 oxidation in 16O2+18O2
SiCSiO2 SiCSiO2
Challenges in SiC technology
SiO2
SiC
High density of interface states (Dit)
Instabilities during operation
water vapor: D218O
Water related problems in SiO2/Si
humidity in a clean room fabrication facility is between 30 and 50%
negative oxide charge buildup near the SiO2/Si interface
increases in the interface state density already reported for SiO2/Si
negative-bias-temperature instabilities attributed to water related species at the SiO2/Si interface
Water vapor incorporationin SiO2/SiC and SiO2/Si
G.V. Soares, I.J.R. Baumvol, S.A. Corrêa, C. Radtke, F.C. StedileAppl. Phys.Lett. 95 (2009) 191912
Silicon 4H-SiC(Si Face)
thermalSiO2
thermalSiO2
G.V. Soares, I.J.R. Baumvol, S.A. Corrêa, C. Radtke, F.C. StedileElectrochemical and Solid-State Letters 13 (2010) G95
SiO2 thermal growth: 1100°C, 100 mbar dry natural “16O2”
+ vacuum annealing: 10-7 mbar, 700°C, 30 min
Samples preparation
Water vapor (D218O) treatments: 1h, 200 – 800°C, 10 mbar
D218O
18O – natural abundance of 0.2%
D – natural abundance of 0.015%
Water partial pressure in air of 30% humidity at 25°C
0 1 2 3 4 5 6 7 8 90
1
2
3
4 1000ºC 600ºC
Interface@1000ºC
D c
once
ntra
tion
(1020
at x
cm
-3)
Depth (nm)
0 1 2 3 4 5 300
1
2
3
4
Interface@1000ºC
1000ºC 600ºC
D c
once
ntra
tion
(1020
at x
cm
-3)
Depth (nm)
D profilesin Si16O2/SiC and in Si16O2/Si
D(3He,p)4He at 700 keV
151 153 155 157 151 152 153
151 153 155 157 151 154 157 160 163
Alp
ha Y
ield
(a.u
.)
Proton beam energy (keV)
20°CSiO2/SiSiO2/SiC
Proton beam energy (keV)1000°C
Alp
ha Y
ield
(a.u
.)
Proton beam energy (keV)
Proton beam energy (keV)
18O excitation curves
0 10 20 30 40 500.0
0.1
0.2
0.3
0.4
0.5
0 2 4 6 8 10 12
0 20 40 600
1
2
3
4
0 20 40 60 80 100
Depth (nm)
20°C
Depth (nm)18O
con
cent
ratio
n (1
022 a
t x c
m-3) SiO2/Si
18O
con
cent
ratio
n (1
022 a
t x c
m-3)
Depth (nm)
1000°C
SiO2/SiC
Depth (nm)
18O profiles
Experimental
RF Sputtering conditions:- Target: SiO2, 90 W- 2 mtorr of Ar, flux of 20 sccm
Deposition on Si and on 4H-SiC substrates
Deposition rate ~ 0.1 Å/st = 2,000 s
20 nm
Silicon
dep. SiO2
4H-SiC(Si-face)
dep. SiO2 20 nm
200 400 600 800
0
20
40
60
80
100
4H-SiC Si
D a
real
den
sity
(1013
at.c
m-2)
D218O annealing temperature (°C)
Temperature and substrate influence in D2
18O vapor incorporation
Substrate
20 nm SiO2 dep.
D(3He,p)4He at 700 keV
HF
remaining D~ 90%
18O profiles
152 154 156 158 160 162
600 °C ( thermal)600 °C (deposited)800 °C (deposited)
Cou
nts
(u.a
.)
Proton energy (keV)
0 5 10 15 20
1
2
3
4
18O
con
c. (1
022 a
t.cm
-3)
Thickness (nm)
+ 10 mbar D218O, 1h
E. Pitthan et al. Appl. Phys. Lett. 104 (2014) 111904
SiO2/SiC
Further research topics
Mechanism and limiting step of thermal growth of SiO2 on SiC Annealings in D2 of SiO2 / 4H-SiC and SiO2 / 6H-SiC
structures with and without Pt Annealings in NO of Pt / SiO2 / SiC structures Reoxidations and sequencial annealings em H2O2
Oxidations in 18O2 of 6H and 4H-SiC (Si and C-faces) varying P, t and T
Brief thermal growth followed by SiO2 deposition Nitridation in 15NH3 of SiC and of SiO2 /SiC folllowed by SiO2
deposition CO annealings of SiO2 / SiC and SiO2 / Si structures Incorporation and quantification of P in SiO2 / SiC
Thank you!
Working
reservoir
18O2
furnace
LiquidN2
18O gas2
Working
reservoir
18O2
furnace
Zeolite
RECOVERYbottle bottle
Manipulation and Recovering of 18O2
Expensive gas: about U$ 1,000/L
(97% enriched in the 18O isotope)
Natural Oxygen: 99.759% 16O 0.204% 18O 0.037% 17O
Manipulation and Recovering of D218O
VERY expensive : about U$ 2,000/mL !!!
Working
vaporBottle
D O218
furnace
ValveV2
ValveV1
liquidD OBottle
218
furnace
ValveV2
ValveV1
liquidD OBottle
218
LiquidN2
D O vapor218
RECOVERY
0 100 200 300 400 5000
500
1000
1500 18O(p, ) 15N
Channel
O2 natural:99,759% 16O0,204% 18O 0,037% 17O
18O2 97%
Utilizando NRP para compreender o transporte atômico durante a oxidação do Si
SiO2
Si
Espécies móveis durante a oxidação? Resultados:
18O2
oxigênio é a espécie móvel, e que se desloca de duas maneiras: -Por difusão, interagindo com os defeitos de rede( região superficial)- Intersticialmente, sem reagir com o óxido já formado até chegar à interface com o semicondutor e reagir formando SiO2
SiO2
SiSi18O2
in thermal growth of silicon oxide films on Si in dry O2
I.J.R. Baumvol, C. Krug, F.C. Stedile, F. Gorris, W.H. SchultePhys. Rev. B 60 (1999) 1492
Ions decelerator
PpSi 3029 ),( ER = 417 keV; =100 eV
Alcance das partículas no Mylar
Electronic and nuclear dE/dx
Energy loss
Vacuum Solid
0 xDepth
2222 cossin
ti
iiti mm
mmmk
Interpretation: SPACES code I. Vickridge and G. Amsel, Nucl. Instr. and Meth. B 45 (1990) 6
Narrow Resonance Nuclear Reaction Profiling: NRP
g0
FLATUSbeam particle energy, mass and atomic number; energyloss per unit length and energy straggling correspondingto the material and energy of interest
AUTOCONVOLUTION FILE
convolution with resonance line shape (assumedLorentzian) and width, ion beam energy spread(assumed Gaussian) and its widening due to the Dopplereffect at room temperature (assumed Gaussian), andconcentration of the probed nuclide and thickness ofeach layer of a first temptative profile
THEORETICAL EXCITATION CURVE
Convolution
I. Vickridge, Thesis, University of Paris VII (1990)
Modeling
0
0*
000 )(*)(*)(.)( EEfKEhEcEN nn
G. Amsel, et al., Nucl. Instr. Meth., v. 197, n. 1, p. 1 (1990).
0
)(!)( dxxCe
nmxK mx
n
n
0 )( 0Eh
?)( xC
22
33
5577
99 1111 1313
nf *dE/dxS2
Er
1965: modelo de Deal e Grove p/ oxidação térmica do silício
Principais suposições:
- existência de uma camada de óxido inicial (~ 20 nm);
- regime estacionário;
- difusão de O2 através do filme de óxido de silício e reação na interface SiO2/Si.
Deal and Grove, JAP 36, 3770 (1965)
Exemplo de Aplicação: 18O em Si
Osbourne Executive produzido nos anos 80 x iPhone em 2009:28.75 pounds / 135g = 100 x + pesado4MHz / 412 MHz = 100 x + lento$2500 / $200-300 = 10 x + caro(52cm x 23cm x 33cm)/(115mm x 61mm x 11.6mm) = 485 x maior
Mecanismo e Etapa Limitante do Crescimento Térmico de SiO2 sobre SiC
Traçagem Isotópica – 16O /18O
18O(p,)15N Ep = 151 keV
6H-SiC tipo n polidasnas faces (0001) e (0001)e Si (001)
0 175 180 1850
50
100
18 O
(%)
Thickness (nm)
Thickness (nm)
18 O
(%)
0 65 70 750
50x 3
SiO2 SiC6H SiC(0001)
Si(001) Si
I.C. Vickridge et al., Phys. Rev. Lett. 89 (2002) 256102
Limpeza das amostras
Si16O2Si18O2 SiC ou Si
1o grupo de amostras
1100 oC 100mbar 16O2 Si45 h8 h
InterfacesIdênticas
SiC
Si16O2Si18O2 SiC or Si
1100oC 100 mbar 1h 18O2
InterfacesIdênticas
HF: taxa de ataque ~ 1 nm/s70 s30 s
40 s20 s
30 s10 s
1 s1 s
SiSiC
0.0 4.0 8.0 12.0 16.0
SiO2 / SiC (0001)
Alph
a Yi
eld
(arb
itrar
y un
its)
0.0 2.0 4.0 6.0
SiO2 / Si (001)
SiO2 / SiC (0001)
E - E R (keV)
0.0 10.0 20.0 30.0
0 4 8 120
50
100
x 3
18 O
(%)
Thickness (nm)
0 120 1500
50
100 0 60 800
50
100Interfaces SiO2/SiC
Limpeza das lâminas
1100oC 100 mbar 18O2 1h
1100oC 100 mbar 16O2
16 h 26 h 35 h 45 h
SiC ou SiSi16O2Si18O2
Interfacesdistintas ?
2º grupo de amostras
0.0 10.0 20.0 30.0
E - E R (keV)0.0 2.0 4.0 6.0 8.0
0.0 4.0 8.0 12.0 16.0
SiO2 / Si (001)
SiO2 / SiC (0001)
SiO2 / SiC (0001)Alph
a Yi
eld
(arb
itrar
y un
its)
0 4 8 12 160
50
100
x 3
Thickness (nm)
18 O
(%)
0 140 160 1800
50
100
0 40 600
50
100
0.0 10.0 20.0 30.0
E - E R (keV)0.0 2.0 4.0 6.0 8.0
0.0 4.0 8.0 12.0 16.0
SiO2 / Si (001)
SiO2 / SiC (0001)
SiO2 / SiC (0001)Alph
a Yi
eld
(arb
itrar
y un
its)
Interfaces SiO2/SiC
Colaboradores atuais
Doutorando: Eduardo Pitthan FºIC: Gustavo Dartora
Profs. Gabriel V. Soares, Henry Boudinov – IF UFRGS Profs. Cláudio Radtke – IQ UFRGS Prof. Rodrigo Prioli Meneses – DF PUC-RJ Prof. Sima Dimitrijev, Griffith University, Australia Prof. Leonard Feldman, Rutgers University, E.U.A. Dr. Aivars Lelys, Army Research Lab., E.U.A. Dr. Anant Agarwal, Cree Inc.→ DOE, E.U.A.