1 Eric Garfunkel Departments of Chemistry and Physics Rutgers University Piscataway, NJ Key interactions: Gustafsson, Bartynski, Chabal – Rutgers Gennadi Bersuker – Sematech Rich Haight, Supratik Guha – IBM Other collaborators: M. Green – NIST; E. Gusev - Qualcomm; W. Tsai – Intel; J. Chambers, H. Niimi – TI Advanced Gate Stacks and Substrate Engineering
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Eric Garfunkel Departments of Chemistry and Physics ... of Chemistry and Physics Rutgers University Piscataway, NJ ... Sematech Rich Haight, Supratik Guha – IBM Other collaborators
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Eric GarfunkelDepartments of Chemistry and PhysicsRutgers UniversityPiscataway, NJ
Use high resolution characterization methods to: i. Determine composition, structure and electronic properties
gate stacks that use new (post-Si) materials ii. Help determine physical and chemical nature of radiation
induced defects
4
Results
Generated thin films with high-K dielectrics (HfO2) and metal gate electrodes (Al, Ru).Performed ion scattering, photoemission, internal and inverse photoemission on selected systems.Had samples irradiated by Vanderbilt group (Feldman), as well as at Rutgers.Performed conductive tip SPM measurements of defects on selected systems
5
75 80 85 90 95
×5
depth
Zr
SiO
Scat
tere
d Yi
eld
(a.u
.)
Proton Energy (keV)
ZrO2
(ZrO2)x(SiO2)y
Si(100)
~100 keV p+
depth profile
0 10 20 30 40 50 60 700.0
0.5
1.0
1.5
2.0
MEIS depth profiling
Si
ZrO2.04
Zr
O
Con
cent
ratio
n
Depth (Å)
Sensitivity:≈ 10+12 atoms/cm2 (Hf, Zr)≈ 10+14 atoms/cm2 (C, N)Accuracy for determining total amounts:≈ 5% absolute (Hf, Zr, O), ≈ 2% relative≈ 10% absolute (C, N)Depth resolution: (need density)≈ 3 Å near surface≈ 8 Å at depth of 40 Å
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Nitride barrier monolayers to minimize diffusion
• Nitride barrier layers helpful to slow O, Si and dopant diffusion, as well as silicate formation and other interface reactions.
• Nitridation also raises crystallization temperature.
75 80 85 90 950
100
200
300
400
500
600
700
×2
0Å
0ÅN O
Si
Hf
Yie
ldEnergy (keV)
ONitride barrier layers?
Si
SiO2
MOx
Si
0 10 20 30 40 50
0.0
0.2
0.4
0.6
950oC 800oC
700oC610oC
Com
posi
tion
Depth [Å]
as is
500oC
7
105 110 115
HfO2
18O
16O
Yie
ld (a
.u.)
H+ energy (keV)
Si
105 110 115
HfO2SiO2
18ON
16O
Yie
ld (a
.u.)
H+ energy (keV)
Si
x = 0% 33% 50%
105 110 115
(HfO2)2SiO2
18ON
16O
Yiel
d (a
.u.)
H+ energy (keV)
Si
HfO2(SiO2)x re-oxidation in 18O: 500°C, 10-2 Torr, 30 min
Isotope reactions and diffusion in silicatesRelation between composition and O incorporation
• strong exchange reaction even at 500°C: 16O loss, with same total O conc.• no change in width of 16O and Si peaks (no formation of interfacial oxide)• exchange rate decreases with increase of SiO2 fraction x• 50:50 mix of SiO2:HfO2 is enough to suppress oxygen exchange (in this case)
Rutgers/Sematech
8
Exchange and growth T-dependence
0 500 600 700 800 900 10000
3
6
9
12
Oxy
gen
in H
f sili
cate
laye
r [at
oms/
cm2 ]
Tx [C]
O18 O16 O sum
0 500 600 700 800 900 10000
3
6
9
12
Inte
rfaci
al o
xyge
n co
ncen
tratio
n [a
tom
s/cm
2 ]
Tx [C]
O18 O16 O sum
• Due to exchange reactions, the 18O in (HfO2)2(SiO2) layers increases, 16O decreases, with the total oxygen content constant.
• There is higher 16O density at the interface (16O/18O >1) at Tx=500-700oC (oxygen or vacancy exchange mechanism)
• Interface 16O/18O changes at Tx≥800oC due to (a) higher 18O equilibrium concentration(b) opening of direct paths through (HfO2)2(SiO2)
SiOxNy
Si
(HfO2)2(SiO2)
0.8 1.0 1.20.1
1
10
Inte
rfaci
al O
[x
1015
ato
ms/
cm2 ]
1000/T [K-1]
Hf2SiO6/SiOxNy
SiO2
SiOxNy
Interaction of metal overlayers with dielectric
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)
After UHV anneal at 300oC for 15 min:Lowering and broadening of Ti peakHf and Si peak shift and O peak change
⇒ Ti layer oxidation
100 104 108 112 116 120 124 1280
600
1200
1800
2400
Yie
ld
Energy [keV]
as deposited 15 min UHV anneal 300oC Hf
Ti
Si
O
surfint
x10
Si (100)
HfO2.07
SiO2
27Å
6ÅTi
RT
27Å
7Å 300oC
UHVSi (100)
HfO2
SiO2
Ti
Si (100)
HfO1.9
HfSiOx
TiOx
10
Interface chemical stability: Heats of oxide formation of most stable oxides and XPS results demonstrating interface reactivity
MEIS spectra of low energy dopant implants: ultrashallow junctions
0 10 20 30 40 50 60 701E20
1E21
1E22
As c
once
ntra
tion
(cm
-3)
Depth (Å)
Depth profile derived from the As MEIS peakDepth profile of As in Si from a low
energy implant (1kV, ~1015 As/cm2)
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Arsenic (As) behavior in SIMOX vs. bulk-Si
Interaction of As with vacancies following higher E implants…
After annealing:
• Si interstitials remain in bulk-Si, but NOT in SIMOX
• excess vacancies annihilate Si interstitials in SIMOX
• SIMOX crystal quality is excellent, especially for RTA
0.0
0.5
1.0
1.5
2.0
2.5
75 80 85 90 95 1000.0
0.5
1.0
1.5
2.0
2.5
O
Si
As
RTA 1000ºC/10s
SIMOX Si
Cou
nts
FA 950ºC/15min
SIMOX Si
Energy (keV)
Si interstitials
13
Alternative Channel MaterialsMobility improves by straining Si, but CMOS scaling demands further improvements….try other semiconductors!Key challenge for alternative channel materials is the dielectric – need low interface and bulk defect concentration Also need high Ion/Ioff ratio, appropriate integration, high thermal stability, appropriate band alignment with no Ef pinning, etc.Ge and SiGe studied extensively for years - IBM, Intel…III-V compound semiconductors now being seriously considered for CMOS –Motorola/Freescale, Agere, Intel, IBM, IMEC…
from IBM
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HfOxHfOx/Ge (ALD and MOCVD)/Ge (ALD and MOCVD)Film properties very Film properties very gowthgowth dependentdependent
80 84 88 92 960
1000
2000
Cl
Yie
ld
Energy [keV]
Experiment Total Spc Hf Ge O Cl
Hf
OCl
Ge76 78 80 86 88 90
200
300
400 O
Yie
ld
H+ Energy [keV]
ALD little interfacial GeOx (within sensitivity of the measurements)some Cl accumulation at the interfacesome epitaxial growth
MOCVD HfGe and HfGeOx intermixing (condition dependent)surface Ge (supressed by Ge nitridation)
IntPES: Al / HfO2 / GeNegative Bias on Ge, ΦGe/ HfO2 : ~3.1 eV
2 3 4 5 6
Y1/2 (A
U)
Photon Energy (eV)
-0.05V -0.075V -0.1V -0.125V
0.14 0.16 0.18 0.20 0.22 0.242.76
2.78
2.80
2.82
2.84
2.86
2.88
Bar
rier H
eigh
t (eV
)
E1/2 (MVcm-1)1/2
HfO2/Ge Barrier Height
2.75 3.00 3.25 3.50
Y1/2 (A
U)
Photon Energy (eV)
Ec
EF
EV
φbarrier
metal semiconductor
EF
high-κ
ΦGe~3.1 eV
EF
Al HfO2 Ge
EC
EV
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Scanning probe measurements of topography and dielectric properties
27
tapping mode current image
AFM and current image of unirradiated HfxSiyOz/Si film
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Left: tapping mode Right: current image
AFM and current image of irradiated HfO2/Si filmflux is ~2x1015 H+/cm2 H+~100keV
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AFM images of HfO2/SiON/SiBefore (a) and after (b) radiation exposure ~1015 ~
200keV He2+
(a) (b)
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Conductive Tip AFM Image and I-V Behavior of a Ru/HfO2/Si Stack
-6 -4 -2 0 2 4 6
1
10
100
log[
I(pA
)]
Bias (V)0.2 0.4
-6
-4
-2
0
ln(I/
V2 )
1/V-4 -2 0 2 4
-2
-1
0
1
2
I (pA
)
Bias (V)
For simple F-N tunneling with an electron effective mass of 0.18, the HfO2/Si conduction band barrier height is 1.4eV
Image physical and spectroscopic behavior of radiation induced defects
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PlansGeneration broader range of films and devices with high-K dielectrics (HfO2) and metal gate electrodes (Al, Ru, Pt).Interface engineering: SiOxNy (vary thickness and composition)Expand physical measurements of defects created by high energy photons and ions using SPM and TEMCorrelate physical measurement results with electrical methods. Develop quantitative understanding of behavior as a function of particle, fluence and energy.Monitor H/D concentration and profiles, and effects on defect generation (by radiation) and passivation.Determine if radiation induced behavior changes with new channelmaterials (e.g., Ge, InGaAs), strain, or SOIExplore effects of processing and growth on radiation behavior.Correlate with first principles theory.