Nuclear reaction analysis and narrow profiling

fernanda.stedile@ufrgs.br

Fernanda Chiarello Stedile

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.