radiation effects on emerging electronic materials and devices leonard c. feldman vanderbilt...
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![Page 1: Radiation Effects on Emerging Electronic Materials and Devices Leonard C. Feldman Vanderbilt University Department of Physics and Astronomy Vanderbilt](https://reader036.vdocuments.net/reader036/viewer/2022062422/56649ec05503460f94bcc3db/html5/thumbnails/1.jpg)
Radiation Effects on Emerging Electronic Materials and Devices
Leonard C. FeldmanVanderbilt University
Department of Physics and AstronomyVanderbilt Institute on Nanoscale Science and Engineering
June 13/14, 2006
Radiation Effects in Emerging Materials
Overview
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Gate
oxid
eSi
met
al
MOS Schematic
Gate Dielectricsi. High-k on Si:
HfO2/Si, HfSiO/Si - (w and w/o interlayer)ii. High-k on Ge: HfDyO2/Geiii. SiO2/Silicon carbide
MURI review June’06
Radiation damage in emerging materials
Other emerging materialsi. Strained siliconii. SOIiii. SiGe
Characterization: i. Electrical:
CV - Net charge
Photo-CV - Deep and slow states
I-V - Breakdown
ii. Optical:
Femto-second Pump-probe spectroscopy - alternate approach to charge quantification
iii. Atomic level spectroscopy:
Conductive tip AFM - identification of isolated leakage spots
X-ray absorption - defect selective
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+ +
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GoalsThe goals of this segment of the program are to identify and associate:
i) radiation induced electrical defects with particular physical (atomic and electronic) configurations
ii) to identify and elucidate new defects/traps that exist in emerging materials
Requires a strong coupling to theory
Requires strong coupling to sophisticated electrical
New materials also give new insights that feed-back to the traditional structures
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In situ photovoltage measurements using femtosecond pump-probe photoelectron spectroscopy and its application to metal-HfO
2-Si structures
Richard HaightIBM
Measures band-bending in an in-situ configuration, without metal gate, yielding intrinsic electronic structure
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800 nm ~35fs
HARMONIC LASER PHOTOEMISSION
TOF detector
sample
parabolic mirror
Main Chamber
grating
Ar jet
Pump, 800 nm, ~35fs
High Harmonic Generation
ee
High KE
Photon energiesfrom 15-60 eV
Laser field
Harmonic photon
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p-FET
n-type
p+ p+
gate oxide
channel
Metal Gate for high-K MOS?
But
1) Metal gate shows a similar problem
EIFL Midgap
2) In addition, Vt instability: charge trap?
Goal: Understand the effect of thermal processes on high-K oxide & oxide-metal interface which affect MOS properties
Si
N-silicon
HfO2
High WF Metal
EF
For ideal p-FET
at VG= 0
Interface Fermi Level (EIFL)
Vacuum level
Sze: Phys. Semi. Dev.
After anneal
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Advanced Gate Stacks and Substrate Engineering
Eric Garfunkel, Rutgers University
External interactions:
• Rich Haight, Supratik Guha – IBM• Gennadi Bersuker – Sematech
• M. Green - NIST• E. Gusev - Qualcomm• W. Tsai - Intel• J. Chambers - TI
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Rutgers CMOS Materials Analysis
• Scanning probe microscopy – topography, surface damage, electrical defects
• Ion scattering: RBS, MEIS, NRA, ERD – composition, crystallinity, depth profiles, H/D
• Direct, inverse and internal photoemission – electronic structure, band alignment, defects
• FTIR, XRD, TEM• Electrical – IV, CV
• Growth – ALD, CVD, PVD
Use high resolution physical and chemical methods to examine new materials for radiation induced effects and compare with Si/SiO2/poly-Si stacks
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Total dielectric thickness from RBS: ~10 to 11 nm
RBS & CV of HfSiO/SiO2/p-Si films
Physical characterization Electrical characterization
Total dielectric thickness from CV: ~12 nm
E0 = 1.4 MeV 4He
E1 = KE0
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Electron Traps in Hf-based Gate Stacks
G. Bersuker, C. Young, P. Lysaght,
R. Choi, M. Quevedo-Lopez,
P. Kirsch, B. H. Lee
SEMATECH
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Electron Trap Depth profile
0.0 0.6 0.8 1.0 1.20
10
20
30
40
50
60
701.1nm SiO
2/3nm HfO
2/TiN
Initial After 300s After 600s After 900sN
t [10
10/c
m2 ]
Probing Depth [nm]
nFET W/L = 10/1 mtr, t
f = 100 ns
Vamp
= 1.4 VV
base = -0.7 V
Vstress
= 2.4 V • Factors affecting conversion of frequency to distance:– Capture cross sections
decrease exponentially with depth
– Recombination rate is limited by the capture of holes
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Electron Trap Profile in High- Layers
0 1 2 3 4 5
0
10
20
30
40
50
tr,t
f = 100 ns
PW = 100 s
Interfacial Layer/High-/Anneal ambient SiO
2/MOCVD HfO
2/N
2
HF-Last/MOCVD HfO2/N
2
SiO2/ALD HfO
2/N
2
HF-Last/NH3/ALD HfO
2/NH
3
Ntr
ap [
1012
/cm
2 ]
Distance from Gate [nm]
• Electron traps uniformly distributed across the high-k film thickness
• No significant difference in trap density between deposition methods and anneal ambients
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Differences Between the Trapping States in x-ray and -Ray Irradiated Nano-crystalline HfO2, and Non-
crystalline Hf SilicatesG. Lucovsky, S. Lee, H. Seo, R.D. Schrimpf, D.M.
Fleetwood, J. Felix, J. Luning,, L.B. Fleming, M. Ulrich, and D.E. Aspnes
Aim: The correlation of electronically active defects in alternate dielectrics with spectroscopic/electronic details extracted primarily via (soft) x-ray spectroscopies.
i) Processing defects which act as traps for radiation generated carriers
ii) Defects created by the radiation itself.
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G. Lucovsky
NCSU
Electronic Structure
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spectroscopic studies of band edge electronic structure band edge defects - trapping asymmetry n-
type Si substrates
EOT~7 nm
IMEC group/NCSU
e-traps ~ 0.5 eV below HfO2 CB
h-traps ~ 3 eV above HfO2 VB
1000
104
0 2 4 6 8 10 12 14 16
6p
6s
O2pnb
O-vacancydefect
HfO2
SXPS 60 eV
ph
oto
ele
ctr
on
co
un
ts
binding energy (eV)
5d5/2
T2g
5d3/2
Eg
0.01
0.1
1
5 5.5 6 6.5 7 7.5 8 8.5 9
photon energy (eV)im
ag
inar
y p
art
of
die
lect
ric
co
nst
an
t (
2)
Eg (2 features)
band edge"defect state"
HfO2
S. Zollner,D. Triyoso
0
500
1000
1500
2000
2500
3000
3500
4000
4.5 5 5.5 6 6.5
ZrO2
V.V. Afanas'evA. Stesmans
photon energy (eV)
[ph
oto
co
nd
uc
tivi
ty]1
/2 (
arb
. u
nit
s) Eg band edge
feature
band edge"defect state"
negatively charged O-atom vacancy
0
500
1000
1500
2000
2500
3000
3500
4000
4.5 5 5.5 6 6.5
ZrO2
V.V. Afanas'evA. Stesmans
photon energy (eV)
[ph
oto
co
nd
uc
tivi
ty]1
/2 (
arb
. u
nit
s) Eg band edge
feature
band edge"defect state"
negatively charged O-atom vacancy
1000
104
0 2 4 6 8 10 12 14 16
ph
oto
ele
ctro
n c
ou
nts
binding energy (eV)
4p
3d3/2
Eg
3d5/2
T2g
O2pnb
4s
4p
TiO2
SXPS 60 eV
O-vacancydefect
defects: ZrO2 (PC): TiO2 (SXPS)
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Damage fundamentals: SiO2 vs HfO2
Proton stoppingpower
X-ray mass attenuationcoefficient
For same capacitance ---- ~6 times more thickness
HfO2 =CAP
HfO2 =CAP
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Silicon Carbide CollaborationVanderbilt: Sriram Dixit, Sarit Dhar, S.T.
Pantelides, John Rozen
Auburn: J. Williams and group
Purdue: J. Cooper and group
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Silicon Carbide and SiC/SiO2 Interfaces
Silicon carbide as a radiation damage resistant material
i) High temp, high power applications
ii) SiC-based neutron, charged particle detectors with improved radiation resistance
iii) Materials improvements at all levels in recent years
SiC/SiO2(N) Interfaces
i) “Reveals” new, SiO2 radiation induced defects that fall within the SiC band-gap—4H, 6H, 3C, Si—a form of spectroscopy
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N+ Source
Implanted P-Well
N- Drift Region
Oxide
SiO2Surface RoughnessDue to P-TypeImplant Anneal
SiC
MOSFETChannelResistance
Transition Layer
SiC
SiO2
Dangling Bonds
Si - Si Bonds
C - C Bonds
SiC Power MOSFET
N+ SubstrateN+ Substrate
GateSource (VSD)
N+
P base
Drain
N- drift region
SiO2
SiC
ISD
R = Rchan + Rintrinsic
Rchan ~ (mobility)-1
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Ev
Ec
sp3 hybrid sp3 hybrid
Bonding orbital
Antibonding orbital
Valence bands
Conduction bands
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Logistics & MURI Collaborations
Samples, Processes, DevicesRutgers, Sematech, NCSU
Materials & Interface AnalysisRutgers, NCSU and IBM
Radiation ExposureVanderbilt
Post-radiation CharacterizationVanderbilt, Sematech, NCSU, Rutgers
and IBM
TheoryVanderbilt
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Plans• Generation 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 TEM, in correlation with electrical methods.
• Develop quantitative understanding of behavior as a function of particle, fluence, energy
• Monitor H/D concentration and profiles, and effects on defect generation (by radiation) and passivation.
• Determine if radiation induced behavior changes with new channel materials (e.g., Ge, InGaAs), strain, or SOI
• Explore effects of processing and growth on radiation behavior.• Correlate with first principles theory.
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10:40 Overview: Radiation Effects in Emerging Materials
Leonard Feldman, Vanderbilt University11:00 Radiation Damage in SiO2/SiC Interfaces
Sriram Dixit, Vanderbilt University11:20 Spectroscopic Identification of Defects in Alternative Dielectrics
Gerry Lucovsky, North Carolina State University12:00 Lunch – Room 1061:00 Radiation Effects in Advanced Gate Stacks
Eric Garfunkel, Rutgers UniversityG. Bersuker, SEMATECH
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SiO1.99 0.02
SiO2.01 0.02
SiO1.99 0.02
SiO2.01 0.02
RBS/CH
SiO2
“No” carbon
SiO2/SiC
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Interface State Density-----6H-4H Polytypes
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Results
• Generated thin films with high-K dielectrics (HfO2) and metal gate electrodes (Al, Ru).
• Performed ion scattering, photoemission, internal photoemissions and inverse photoemission….on selected systems.
• Had samples irradiated by Vanderbilt group (Feldman)• Performed SPM measurements of defects on selected
systems