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

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

++

+ +

++

- -

- -

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

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

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

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

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

• 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

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

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

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

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

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.

G. Lucovsky

NCSU

Electronic Structure

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)

Damage fundamentals: SiO2 vs HfO2

Proton stoppingpower

X-ray mass attenuationcoefficient

For same capacitance ---- ~6 times more thickness

HfO2 =CAP

HfO2 =CAP

Silicon Carbide CollaborationVanderbilt: 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

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

-----

Ev

Ec

sp3 hybrid sp3 hybrid

Bonding orbital

Antibonding orbital

Valence bands

Conduction bands

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

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 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

SiO1.99 0.02

SiO2.01 0.02

SiO1.99 0.02

SiO2.01 0.02

RBS/CH

SiO2

“No” carbon

SiO2/SiC

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