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Role of Stress and Solution Chemistry for Reduced Damage During CMP of Ultra-Low-k Materials
July 17, 2007July 17, 2007
Taek-Soo Kim1, Katherine Mackie1, Qiping Zhong2, Maria Peterson2, Halbert Tam2, Tomohisa Konno3, and Reinhold H. Dauskardt1a be t a , o o sa o o , a d e o d aus a dt
1Stanford University, Stanford, CA 94305 USA2JSR Micro, Inc., 1280 N. Mathilda Ave., Sunnyvale, CA 94089, USA
33JSR Corporation, Yokkaichi Research Center, 100 Kawajiri-cho, Yokkaichi, Japan
Reliable Processing of Interconnect Structures Applied CMP down force
Applied CMP shear loadSi Via Low-k
abrasiveCMP Slurry
ULKcracking delaminationσf
P
nano-scaledefect
Via Low k
PAD0.1 μm
ff t f t l
silicon device
effect of metal density and aspect ratio
thermomechanical reliability of low k films
Process yield and yreliability determined by the evolution of defect
CMP and package contact stresses
soft/ductile buffer layers
cracking depends on flux composition
Crack Driving Force
Applied CMP down forceP
elastic-plastic contact
Applied CMP down force
Applied CMP shear loadSi
cracking d l i ti
σf
Crack Driving ForceGGGG ++
abrasiveCMP Slurry
ULKcracking delaminationσf
CMPcontactfilmtotal GGGG ++=
f
fffilm E
hZG
2σ=
2Pχ l ti l ti
film stressP
PAD damage initiated by abrasive or pad asperity
3aEPG
fcontact ⋅
⋅=χ elastic-plastic
contact
),( pressureshearfnGCMP =
In the absence of chemically active environmental species, crack propagates if
2( / )total cG G J m≥
Environment-Assisted Cracking
Applied CMP down forceStress: applied, residual Silicon
OApplied CMP shear load
Si
ULKcracking delaminationσf δ-
H2O δ+
Oxygen
CMP aqueous
OH-
PAD
abrasiveCMP Slurryf
P
Strained crack tip bonds
δsolution OH
p
2stressSi O Si H O Si OH Si OH− − + ⎯⎯⎯→ − + −stressSi O Si OH Si OH Si O− −− − + ⎯⎯⎯→ − + −
In the presence of chemically active species, crack propagates even if
2( / )total cG G J m< Kinetic fracture
Load Relaxation Crack Growth Technique Double Cantilever Beam (DCB) Specimen
Liquid environment Delaminator v4.0
SiSi
UKD
CMP aqueous solution
Solution container
aqueous pH 11/d
t (m
/s)
10-5
10-4
Po
aqueouspH 3
pH 11
pH 4.5 3%H2O2
Velo
city
, da/
10-7
10-6
Load
, Pa
dP/dt
auto analysis pck
Gro
wth
V
10-10
10-9
10-8
threshold crucial for reliabilityC
rack
Len
gth,
a
da/dt
auto analysis
System and support:DTS Company, Menlo Park, CA (dauskardt@stanford.edu)
10-111 2
Cra
c
Applied Strain Energy Release Rate, G (J/m2)
10 reliabilityC
Time (s)
Relevance to CMP Damage Thierry FARJOT – Patrick LEDUC. LETI
NH4OH 79Citric acid 70TMAH 68DI water 65H2O2 50
45 s CMP
NH4OHDI waterCitric acid
10-4
10-3
a/dt
(m/s
)
NH4OH
DI Water Citric Acid TMAH H2O2
10-3
(m/s
)
TMAHH2O2
10-6
10-5
Gro
wth
Rat
e, d
a
10-4
NH4 OH
DI waterocity
, da/
dt
1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 1.810-7
Cra
ck G
Applied Strain Energy Release Rate, G (J/m2)
10
citric acidTMAH
H O. Cra
ck V
elo
40 45 50 55 60 65 70 75 80 85 9010-5
H2O2
Ave.
Area fraction of DelaminationCourtesy of Markus D. Ong and Reinhold H. Dauskardt, MRS Spring Meeting, 2007
Effects of Solution pH on Crack GrowthSilicon Methyl
H2Oδ
Oxygen
-10-5
10-4
Increasing pH accelerates crack δ
δ+
-
10-6
10
da/d
t (m
/s) accelerates crack
growth rates
OH -
δ- --10-8
10-7
owth
Rat
e, d
δ+- δ-
10-10
10-9
o
Cra
ck G
ro
50%RHpH 7
pH 10NH4OH
TaNEpoxy
Si
1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.610-11
10 30oC
2
JSR-LKD 5537
MSSQTa/TaN
Si
Applied Strain Energy Release Rate, G (J/m2)
Alkali metal ion + crack tip decelerated crack growth by crack tip bluntingg y p g
Electrolytes in DI water w/o surfactants
Crack tip gets blunted by dissolution of the silica backbone.
10-5
10-4
m/s
)
Electrolytes in DI water w/o surfactants
Inglis expression for the t t ti
10-7
10-6
Rat
e, d
a/dt
(m
pH 10 (NH4OH)
stress concentration
2 /t aσ σ ρ=
10-9
10-8
Cra
ck G
row
th R
50%RH
pH 7 Wijnen (1989)
Silica gel dissolution in aqueous alkali metal hydroxides
Tomozawa (1996)
1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.610-11
10-10
30oC
C pH 7
pH 10 (KOH)
pH 10 (NaOH)
Wijnen (1989)
JSR-LKD 5537
Applied Strain Energy Release Rate, G (J/m2)
Effects of Nonionic Surfactants on Defect Evolution during CMP
Effects of surfactant molecules on the defect
l ti / k th
Surfactant additions critical for efficient CMP:• enhances wetting of hydrophobic low-k dielectrics
• stabilizes CMP slurry evolution/crack growth are unknown!
stabilizes CMP slurry
• optimized CMP removal rates, reduced dishing…
Silicon
MethylCH3(CH2)m-1O(CH2CH2O)nH
polyoxyethylene alkyl ether
CMP slurry δδ+
-
SiliconOxygenHydrophilic
headHydrophobic
tail
CMP slurry
H2O or OH-
Surfactant molecule
Applied stress
2
Nonionic Surfactants: Polyoxyethylene Alkyl Ethers
CH3(CH2)m-1O(CH2CH2O)nH CmEn
Monomeric surfactant
C i l # f C # f EO Molecular Molarity of 0 1 t%
Hydrophobic hydrocarbon chain
Hydrophilic ethylene oxide (EO) chain
Commercial name
# of C,m
# of EO,n HLB
Molecular weight (g/mol)
0.1wt% surfactant
solution (M)
ETHALL DA-4
10
4 10.5 334 2.99 x 10-3
DA 6 6 12 4 423 2 37 10 3
Hydrophilic-Lipophilic Balance (HLB)lipophilic 1 20 hydrophilic10DA-6 6 12.4 423 2.37 x 10-3
DA-9 9 14.3 555 1.80 x 10-3
ETHALL LA-4 4 9.2 363 2.76 x 10-3
LA 7 7 12 2 495 2 02 10-3
lipophilic 1 20 hydrophilic
(oil soluble) (water soluble)
12LA-7 7 12.2 495 2.02 x 10-3
LA-23 23 16.8 1200 8.34 x 10-4
LA-50 50 18.3 2389 4.19 x 10-4
BRIJ 76 10 12 4 711 1 41 x 10-3
CMC @25˚C
BRIJ 76: 4x10-3 wt%
BRIJ 78: 9.5x10-4 wt%BRIJ 76
18
10 12.4 711 1.41 x 10 3
78 20 15.3 1152 8.68 x 10-4
700 100 18.8 4676 2.14 x 10-4
CmEn Effects on Crack Growth Behavior (in pH 7 NH4OH)
C18 En
10-5
10-4
C10 En
0.1 wt% surfactant 10-5
10-4
0.1 wt% surfactant10-5
10-4
C12 En
0.1 wt% surfactant
10-8
10-7
10-6
Rat
e, d
a/dt
(m/s
)
pH 7 10-7
10-6
Rat
e, d
a/dt
(m/s
)
pH 7E100
8
10-7
10-6
Rat
e, d
a/dt
(m/s
)
pH 7
10-10
10-9
10-8
30oC
Cra
ck G
row
th
E6
E9 10-10
10-9
10-8
30oC
Cra
ck G
row
th R E20
E10
10-10
10-9
10-8
30oC
Cra
ck G
row
th R
E4
E7
E23
E50 JSR-LKD 5537
M k d ff t k th N ff t f f t t l l
1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.610-11
30 C
Applied Strain Energy Release Rate, G (J/m2)
E4E6
1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.610-11
30oC
Applied Strain Energy Release Rate, G (J/m2)
M k d ff t k th
1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.610-11
30 C
Applied Strain Energy Release Rate, G (J/m2)
7
C10 En
Marked effect on crack growthSensitive to hydrophilic chain length
No effect of surfactant molecules
C18 En C12 En
Marked effect on crack growthInsensitive to hydrophilic chain length
CmEn Effects on Crack Growth Behavior (in pH 10 NH4OH)
C10 En C12 En C18 En
10-5
10-4
0.1 wt% surfactant 10-5
10-4
0.1 wt% surfactant 10-5
10-4
0.1 wt% surfactant
8
10-7
10-6
Rat
e, d
a/dt
(m/s
)
pH 10 NH4OH
8
10-7
10-6
Rat
e, d
a/dt
(m/s
)
pH 10 NH4OH
8
10-7
10-6
Rat
e, d
a/dt
(m/s
)
pH 10 NH4OH
10-10
10-9
10-8
30oC
Cra
ck G
row
th R
E4E6
E9 10-10
10-9
10-8
30oC
Cra
ck G
row
th R
E
E23
E50
10-10
10-9
10-8
30oC
Cra
ck G
row
th R
E100
E20
E
1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.610-11
30 C
Applied Strain Energy Release Rate, G (J/m2)
46
1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.610-11
30 C
Applied Strain Energy Release Rate, G (J/m2)
E4 E71.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6
10-11
30 C
Applied Strain Energy Release Rate, G (J/m2)
E10
C10 En
Marked effect on crack growthSensitive to hydrophilic chain length
Little effect of surfactant molecules
C18 En C12 En
some effect on crack growthInsensitive to hydrophilic chain length
Alkali metal ion + EO Complexation
CmEn Effects on Crack Growth Behavior (in pH 10 KOH)
Alkali metal ion + EO Complexation
10-4 KOH pH10 + 0.1wt% surfactant
Carbon
Oxygen
EO of Polyoxyethylene Alkyl Ether
10-7
10-6
10-5
, da/
dt (m
/s)
NH4OH
Metal ion10-9
10-8
10 7
ck G
row
th R
ate
KOH
Okada (1993)
The EO chain locked by the cation stabilzed1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6
10-11
10-10
30oC
Cra
c
C18E10
C18E20C18E100
The EO chain locked by the cation, stabilzed by electron-rich oxygen atoms, decreases mobility
Crack tip blunting effects suppressed by shielding of potassium ion
Applied Strain Energy Release Rate, G (J/m2)
shielding of potassium ion.
Also, complexation reduces hydrogen bonding sites ↓ Gbridging ↓
Nonionic Surfactants: Surfynol 400 Series
CH3 CH3 CH3 CH3I I I I
CH3 – CH – CH2 – C – C ≡ C – C – CH2 – CH – CH3I IO O CH2 CH2CH2 m CH2 nI I
• Dimeric (Gemini) surfactant
• Low foaming (defoaming) and rapid s rface ettingI I
OH OH
m + n = number of moles of ethylene oxide (EO)
and rapid surface wetting
Commercial name Surfynol 420 Surfynol 440 Surfynol 465 Surfynol 485
Ethylene Oxide ContentMoles
Percent by Weight1.320
3.540
1065
3085Percent by Weight 20 40 65 85
Specific Gravity @ 25˚C 0.943 0.982 1.038 1.068
HLB 4 8 13 17
VOC (Volatile Organic Compound) Content (wt %) 28 4 <0.01 <0.01Compound) Content (wt %)
Molecular weight (g/mol) 284 381 667 1548
Molarity of 0.1wt% surfactant solution (M) 3.53 x 10-3 2.63 x 10-3 1.50 x 10-3 6.46 x 10-4
Nonionic Gemini (Dimeric) Surfactants Effects on Crack Growth Behavior
10-4
pH10 KOH + 0.1wt% surfactant10-4
pH 7 + 0.1wt% surfactant
465
pH10 NH4OH + 0.1wt% surfactant10-4
465
10-7
10-6
10-5
e, d
a/dt
(m/s
)
H 1010-7
10-6
10-5
, da/
dt (m
/s)
pH 7
420
440
465
10-7
10-6
10-5
da/
dt (m
/s)
420465
485 pH 10
10-10
10-9
10-8
10
Cra
ck G
row
th R
ate pH 10
KOH
440
485
10-10
10-9
10-8
10
Cra
ck G
row
th R
ate, pH 7
485 10-10
10-9
10-8
10
Cra
ck G
row
th R
ate,
440
485 pH 10NH4OH
1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.610-11
10 10
30oC
Applied Strain Energy Release Rate, G (J/m2)
420440465
1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.610-11
10 30oC
C
Applied Strain Energy Release Rate, G (J/m2)
485
1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.610-11
10 30oC
C
Applied Strain Energy Release Rate, G (J/m2)
440
Low foaming (defoaming) and rapid surface wetting
EO length: S420 < S440 < S465 < S485
Low foaming (defoaming) and rapid surface wetting
accelerated crack growth
Controlling Crack Growth Rate by Surfactant
C18 En10-4
10-4
C10 En10-4
Dimeric surfactant
10-6
10-5
10
/dt (
m/s
)
0.1 wt% surfactant
10-6
10-5
10
/dt (
m/s
)
0.1 wt% surfactant
10-6
10-5
10
/dt (
m/s
)
420
440
4650.1 wt% surfactant
10-9
10-8
10-7
Gro
wth
Rat
e, d
a/pH 7
E100
E20
E10 10-9
10-8
10-7
Gro
wth
Rat
e, d
a/
pH 7
10-9
10-8
10-7
Gro
wth
Rat
e, d
a/ pH 7
1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.610-11
10-10
10
30oC
Cra
ck
1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.610-11
10-10
10
30oC
Cra
ck G
E4E6
E9
1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.610-11
10-10
10
30oC
Cra
ck G
485
No effect of surfactant additions
Applied Strain Energy Release Rate, G (J/m2) Applied Strain Energy Release Rate, G (J/m2)Applied Strain Energy Release Rate, G (J/m2)
Accelerated crack growth Suppressed crack growth
Diffusion of Aqueous Surfactant Solutions into MSSQ
Cleavededge
Diffusion front
Solutions diffuse NSiNx
edge front
200 nmSolutions diffuse into porous films
change RI
Nanoporous ULK
Silicon
500 nm
50 μm
Diffusion of Aqueous Surfactant Solution
(pH 7 NH OH + 0 1wt% C E )(pH 7 NH4OH + 0.1wt% C10En)
1 8x10-3
x Dt=
3
1.2x10-3
1.4x10-3
1.6x10-3
1.8x10 w/o surfactant C10E4
C10E6
C10E9
nce,
x (m
)
Increasing HLB and MWC10E4 (HLB = 10.5) C10E6 (HLB = 12.4) C10E9 (HLB = 14.3)
4.0x10-4
6.0x10-4
8.0x10-4
1.0x10-3
fusi
on D
ista
n
0 200 400 600 800 10000.0
2.0x10-4Diff
Square Root Time, t0.5 (sec0.5)
Diffusion of Aqueous Surfactant Solution
(pH 7 NH OH + 0 1wt% C E )(pH 7 NH4OH + 0.1wt% C12En)
1 4x10-3
1.6x10-3
1.8x10-3
C12E4
C12E7
C Ex (m
)
4
8.0x10-4
1.0x10-3
1.2x10-3
1.4x10
C12E23
C12E50
n D
ista
nce,
x
Increasing HLB and MWC12E4 (HLB = 9.2) C12E7 (HLB = 12.2) C12E23 (HLB = 16.8) C12E50 (HLB = 18.3)
0 200 400 600 800 10000.0
2.0x10-4
4.0x10-4
6.0x10-4
Diff
usio
n
0 200 400 600 800 1000
Square Root Time, t0.5 (sec0.5)
Diffusion of Aqueous Surfactant Solution
(pH 7 NH OH + 0 1wt% C E )(pH 7 NH4OH + 0.1wt% C18En)
4.0x10-4
C18E10
m)
2.0x10-4
3.0x10-4
C18E20
C18E100
stan
ce, x
(m
Increasing HLB and MWC18E10 (HLB = 12.4) C18E20 (HLB = 15.3) C18E100 (HLB = 18.8)
1.0x10-4
Diff
usio
n D
i
0 200 400 600 800 10000.0
Square Root Time, t0.5 (sec0.5)
Diffusion Coefficient (pH 7 NH4OH + 0.1wt% CmEn)
M l l Diff iCommercial name
# of C,m
# of EO,n HLB
Molecular weight,
M (g/mol)
Diffusion coefficient, D (m2s-1)
ETHALL DA-4 4 10.5 334 2.77E-12
x Dt=
11
10DA-6 6 12.4 423 2.19E-12
DA-9 9 14.3 555 1.14E-12
ETHALL LA-4 4 9.2 363 3.12E-12 10-12
10-11
ent,
D (m
2 s-1)
1.85~D M −
12LA-7 7 12.2 495 2.4E-12
LA-23 23 16.8 1200 1.9E-13
LA-50 50 18.3 2389 7.8E-14
10-13
usio
n C
oeffi
cie
-1.85
BRIJ 76
18
10 12.4 711 1.45E-13
78 20 15.3 1152 1.18E-13
700 100 18 8 4676 3 28E-14
102 103 10410-14Diff
u
Molecular Weight (g mol-1)700 100 18.8 4676 3.28E-14
Polymer Reptation Theory
Polymer self-diffusion in polymer melts
Aqueous surfactant solution diffusion in nanoporous MSSQin polymer melts
2~D M −
diffusion in nanoporous MSSQ
2~D M − ?
10-12
10-11
t, D
(m2 s-1
)
1.85~D M −
Experimentally,2.3~D M −
Experimentally,
10-13
10
ion
Coe
ffici
ent
-1.85-2
102 103 10410-14Diff
usi
Molecular Weight (g mol-1)
Data for poly(butadiene)
Jones, Soft Condensed Matter, p. 92
Diffusion of Pure Surfactant in Liquid Phase (C10En)
1 8x10-3
3
1.2x10-3
1.4x10-3
1.6x10-3
1.8x10 C10E4
C10E6
C10E9
nce,
x (m
)
Increasing HLB and MWC10E4 (HLB = 10.5) C10E6 (HLB = 12.4) C10E9 (HLB = 14.3)
4.0x10-4
6.0x10-4
8.0x10-4
1.0x10-3
fusi
on D
ista
n
0 200 400 600 800 10000.0
2.0x10-4
Diff
Square Root Time, t0.5 (sec0.5)
Diffusion of Pure Surfactant in Liquid Phase (C12En)
2.5x10-3
3.0x10-3
C12E4
C12E7(m) C12E4 (HLB = 9.2)
C E (HLB = 12 2)Increasing HLB and MW
1.5x10-3
2.0x10-3
12 7
Dis
tanc
e, x
C12E7 (HLB = 12.2)
0 0
5.0x10-4
1.0x10-3
Diff
usio
n D
0 200 400 600 800 10000.0
Square Root Time, t0.5 (sec0.5)
Diffusion Coefficient (100wt% pure surfactant)
0.1wt% 100wt%
Commercial name
# of C,m
# of EO,n HLB
Molecular weight,
M (g/mol)
Diffusion coefficient, D (m2s-1)
Diffusion coefficient, D (m2s-1)
Hydrophobic tail length
ETHALL DA-4
10
4 10.5 334 2.77E-12 2.72E-12
DA-6 6 12.4 423 2.19E-12 1.99E-12
DA-9 9 14 3 555 1 14E 12 1 44E 12
1/ 2 2 3~ [ ]mD M C − −
10-11
(m2 s-1
)
DA-9 9 14.3 555 1.14E-12 1.44E-12
ETHALL LA-4
12
4 9.2 363 3.12E-12 7.67E-12
LA-7 7 12.2 495 2.4E-12 5.11E-12
Coe
ffici
ent,
D
-2.99
LA-23 23 16.8 1200 1.9E-13
LA-50 50 18.3 2389 7.8E-14
BRIJ 76 10 12.4 711 1.45E-13 10-1 1.5x10-1 2x10-1 2.5x10-1 3x10-1
10-12
Diff
usio
n M1/2C-2 ( 1/2 l-1/2 -2)
1878 20 15.3 1152 1.18E-13
700 100 18.8 4676 3.28E-14
M1/2C 2m (g
1/2mol 1/2m 2)
Increase of Carbon Content by Surfactant Diffusion
Atom % SiNx 200 nm
Ar ion etching (2 mm x 2 mm)
XPS scan (0.1 mm x 0.1 mm)
(1) (2) (3)
O 27 97 42 88 47 82
C10E9 pure surfactantin liquid phase
Nanoporous ULK
x
Silicon
200 nm
500 nmSide view(1) (2) (3)
O 27.97 42.88 47.82
C 41.30 23.84 22.27
Si 30.73 33.28 29.90Top view
0.5 mm
pH7 NH4OH DI water+ 0.1wt% C10E9(1) (2) (3)
O 36.63 45.76 46.01
0.5 mm
45
Diffusion distance
C 35.80 21.61 21.15
Si 27.57 32.63 32.84
25303540
Car
bon
%
C10E9 pure surfactant
0 1 2 3 42025
C10E9 surfactant solution
C
x (mm)
Gibbs-Marangoni Effects
In foams, the Gibbs-Marangoni effect provides a resisting force to the thinning of liquid filmsa resisting force to the thinning of liquid films.
appliedG appliedGapplied applied
bridgingGbridgingG
SiSi
UKD
CMP aqueous solution
bridgingbridging
= −tip applied bridgingG G G
Schramm, 2000
Conclusion
• The growth of damage is a kinetic process involving stress and the presence of active chemical species.
• Careful surfactant additions can control the defect evolution.
C18 En C10 EnDimeric surfactant
Careful surfactant additions can control the defect evolution.
C18 En
10-6
10-5
10-4
(m/s
)0.1 wt%
surfactant
10-6
10-5
10-4
(m/s
)
C10 En
0.1 wt% surfactant
10-6
10-5
10-4
(m/s
)
4204650.1 wt%
surfactant
Dimeric surfactant
10-8
10-7
0
owth
Rat
e, d
a/dt
pH 7E100
E20
E10-8
10-7
10
owth
Rat
e, d
a/dt
(
pH 7
10-8
10-7
10
owth
Rat
e, d
a/dt
(
pH 7440
1 0 1 2 1 4 1 6 1 8 2 0 2 2 2 4 2 610-11
10-10
10-9
30oC
Cra
ck G
ro E10
1 0 1 2 1 4 1 6 1 8 2 0 2 2 2 4 2 610-11
10-10
10-9
30oC
Cra
ck G
ro
E4E6
E9
1 0 1 2 1 4 1 6 1 8 2 0 2 2 2 4 2 610-11
10-10
10-9
30oC
Cra
ck G
ro
485
No effect of surfactant additions
1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6
Applied Strain Energy Release Rate, G (J/m2)
1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6
Applied Strain Energy Release Rate, G (J/m2)
1.0 1.2 1.4 1.6 1.8 2.0 2.2 2.4 2.6
Applied Strain Energy Release Rate, G (J/m2)
Accelerated crack growth Suppressed crack growth
Thank you!Thank you!
Q&AQ&A
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