1

Ion Beam Analysis of the Composition and Structure of Thin Films

Torgny Gustafsson, Physics and

Eric Garfunkel, Chemistry and Chemical Biology

2

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

3

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

5

UHV transfer system for growth and other analysis

6

Atomic Layer Deposition

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2D MEIS Data

2

21

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

18

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