Transcript Radiation damage studies in nitrided & non

June 13/14, 2006
Radiation Effects on Emerging
Electronic Materials and Devices
Radiation Effects in Emerging Materials
Overview
Leonard C. Feldman
Vanderbilt University
Department of Physics and Astronomy
Vanderbilt Institute on Nanoscale Science and Engineering
Radiation damage in emerging materials
Gate Dielectrics
i. High-k on Si:
HfO2/Si, HfSiO/Si - (w and w/o interlayer)
ii. High-k on Ge: HfDyO2/Ge
iii. SiO2/Silicon carbide
+
-
Other emerging materials
+
+
i. Strained silicon
ii. SOI
iii. SiGe
-
+
+
Characterization:
+
i. Electrical:
CV - Net charge
Photo-CV - Deep and slow states
MOS Schematic
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
MURI review June’06
Goals
The 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 feedback to the traditional structures
In situ photovoltage measurements
using femtosecond pump-probe
photoelectron spectroscopy and its
application to metal-HfO2-Si structures
Richard Haight
IBM
Measures band-bending in an in-situ configuration,
without metal gate, yielding intrinsic electronic structure
HARMONIC LASER PHOTOEMISSION
Harmonic photon
Laser field
Photon energies
from 15-60 eV
High Harmonic
Generation
grating
parabolic mirror
TOF detector
e
e
sample
High KE
Main Chamber
Pump,
800 nm, ~35fs
Ar jet
800 nm
~35fs
Metal Gate for high-K MOS?
p-FET
p+
p+
n-type
gate oxide
For ideal p-FET
channel
at VG= 0
Vacuum level
cSi
j
Interface Fermi Level
(EIFL)
Sze: Phys. Semi. Dev.
But
EF
N-silicon
After anneal
1) Metal gate shows a similar problem
High WF Metal
HfO2
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
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
Rutgers CMOS Materials Analysis
Use high resolution physical and chemical methods
to examine new materials for radiation induced
effects and compare with Si/SiO2/poly-Si stacks
• 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
RBS & CV of HfSiO/SiO2/p-Si films
E0 = 1.4 MeV 4He
E1 = KE0
Physical characterization
Electrical characterization
Total dielectric thickness from RBS: ~10 to 11 nm
Total dielectric thickness from CV: ~12 nm
Electron Traps in Hf-based Gate
Stacks
G. Bersuker, C. Young, P. Lysaght,
R. Choi, M. Quevedo-Lopez,
P. Kirsch, B. H. Lee
SEMATECH
Electron Trap Depth profile
1.1nm SiO2/3nm HfO2/TiN
2
50
10
Nt [10 /cm ]
V
= 2.4 V
70 Vstress = 1.4 V
amp
Vbase = -0.7 V
60
40
30
Initial
After 300s
After 600s
After 900s
20
10
0
0.0 0.6
tr, tf = 100 ns
nFET W/L = 10/1 m
0.8
1.0
Probing Depth [nm]
1.2
• Factors affecting
conversion of frequency
to distance:
– Capture cross sections
decrease exponentially
with depth
– Recombination rate is
limited by the capture of
holes
Electron Trap Profile in High-k Layers
50
Interfacial Layer/High-k/Anneal ambient
SiO2/MOCVD HfO2/N2
HF-Last/MOCVD HfO2/N2
SiO2/ALD HfO2/N2
30
HF-Last/NH3/ALD HfO2/NH3
12
2
Ntrap [10 /cm ]
40
tr,tf = 100 ns
20
PW = 100 s
10
0
0
1
2
3
4
5
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
Differences Between the Trapping States in x-ray and Ray Irradiated Nano-crystalline HfO2, and Noncrystalline Hf Silicates
G. 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.
G. Lucovsky
NCSU
Electronic
Structure
spectroscopic studies of band edge electronic structure
4000
HfO2
S. Zollner,
D. Triyoso
[photoconductivity]1/2 (arb. units)
IMEC group/NCSU
imaginary part of dielectric constant (2)
band edge defects - trapping asymmetry n-type Si substrates
1
Eg
(2 features)
0.1
band edge
"defect state"
3500
5.5
6
6.5
7
7.5
8
8.5
2500
2000
1500
band edge
"defect state"
negatively charged
O-atom vacancy
1000
500
0
4.5
9
5
5.5
6
defects: ZrO2 (PC): TiO2 (SXPS)
e-traps ~ 0.5 eV below HfO2 CB
5d3/2 5d5/2
Eg T2g
6s
6p
O2p
nb
4p
1000
O-vacancy
defect
0
2
4
6
8
TiO2
SXPS 60 eV
104
photoelectron counts
photoelectron counts
HfO2
SXPS 60 eV
104
10
12
14
3d5/2 3d3/2
T2g Eg
4s
4p
O2p
nb
1000
O-vacancy
defect
16
binding energy (eV)
h-traps ~ 3 eV above HfO2 VB
6.5
photon energy (eV)
photon energy (eV)
EOT~7
nm
Eg band edge
feature
3000
0.01
5
ZrO2
V.V. Afanas'ev
A. Stesmans
0
2
4
6
8
10
12
binding energy (eV)
14
16
Damage fundamentals: SiO2 vs HfO2
HfO2 =CAP
HfO2 =CAP
Proton stopping
power
X-ray mass attenuation
coefficient
For same capacitance ---- ~6 times more thickness
Silicon Carbide Collaboration
Vanderbilt: Sriram Dixit, Sarit Dhar, S.T.
Pantelides, John Rozen
Auburn: J. Williams and group
Purdue: J. Cooper and group
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
SiC Power MOSFET
Source
(VSD)
SiO2
Gate
C - C Bonds
N+ Substrate
SiO2
Si - Si Bonds
Transition Layer
Dangling Bonds
N+
SiC
P base
ISD
N- drift
region
Surface
Roughness
Due to P-Type
Implant Anneal
SiO2
SiC
SiC
Oxide
N+ Source
Implanted P-Well
Drain
R = Rchan + Rintrinsic
Rchan ~ (mobility)-1
MOSFET
Channel
Resistance
N- Drift Region
-----
Antibonding orbital
Ec
Conduction bands
sp3 hybrid
Ev
sp3 hybrid
Valence bands
Bonding orbital
Logistics & MURI Collaborations
Samples, Processes, Devices
Rutgers, Sematech, NCSU
Materials & Interface Analysis
Rutgers, NCSU and IBM
Theory
Vanderbilt
Radiation Exposure
Vanderbilt
Post-radiation Characterization
Vanderbilt, Sematech, NCSU, Rutgers
and IBM
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.
10:40 Overview: Radiation Effects in Emerging
Materials
Leonard Feldman, Vanderbilt University
11:00 Radiation Damage in SiO2/SiC Interfaces
Sriram Dixit, Vanderbilt University
11:20 Spectroscopic Identification of Defects in
Alternative Dielectrics
Gerry Lucovsky, North Carolina State University
12:00 Lunch – Room 106
1:00 Radiation Effects in Advanced Gate Stacks
Eric Garfunkel, Rutgers University
G. Bersuker, SEMATECH
SiO2/SiC
SiO2.01  0.02
RBS/CH
SiO2
“No” carbon
SiO1.99  0.02
Interface State Density-----6H-4H Polytypes
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