Adhesion and Thermo-Mechanical Reliability in Emerging ...

Reinhold H. Dauskardt ([email protected])Department of Materials Science and Engineering

Adhesion and Thermo-Mechanical Reliability in Emerging Thin-Film Device and Energy

TechnologiesOrganosilicate Films

Mark Oliver, Taek-Soo Kim, Yusuke Matsuda, Scott IsaacsonPolymers and Hybrid Nanomaterials

Jeffery Yang, Ruiliang Jia, Marta Giachino, Chaohui Wang, Linying CuiUltra-Thin Barrier Films

Ryan Birringer and Tissa MirfakhraiChip Package Interactions

Alex Hsing and Ryan BrockPhotovoltaic and Flexible Electronic Materials

Fernando Novoa, Chris Bruner, Stephanie Dupont, Warren Cui

Biological HybridsKrysta Biniek, Olgaby Martinez, Mai Bui, Kemal Levi

…but hybrid films can be fragile and exposed to harsh

environments!

hybridfilm

substrate

solar UV environmental diffusion and

fracture

OPVOTFTTouch Screens PVOLED

Bioscience

skin science sensing and drug delivery

Molecular Hybrid Films in Device Technologies

Outline• Molecular Modeling and Design of Hybrids

• molecular structure and mechanical properties

• High-Toughness Ceramic-Like SiC:H Films• toughening devices with plastic a-SiC:H layers

• Hybrid Materials in Plastic Electronics and OPV • cohesion and adhesion, kinetics and lifetimes

• Biological Hybrid Films and Treatments • biomechanics of human skin, UV exposure and treatment

0

0.5

1

1.5

2

Coh

esio

n E

nerg

y, G

(J/m

2 )

Solar Cells

Quantitative Adhesion/Cohesion and Debond Kinetics

Degradation Kinetics(temp/environment /UV effects)

Adhesion/Cohesion

threshold crucial for reliability

ITO (150 nm )PEDOT:PSS (50-100 nm)

Al (100 nm)Ca (7 nm)

P3HT/PCBM (~150 nm)

• combination of organic and inorganic components from molecular to macro length scales enables materials with multifunctional property sets

• opportunity to tailor mechanical, thermal, electrical, and optical properties

100 nm 1 m 100 m 1 mm

Molecular Hybrids

Å 10 nm

Bottom‐Up Design of Multifunctional Hybrid Materials

High Performance Adhesion

Functionally Graded Hybrids

grad

ed c

ompo

sitio

n

substrate

toughened epoxytoughened epoxy

Functionally-Graded Hybrid Layers for High-Performance Adhesion

epoxy-functionalized silane (GPTMS)

metal alkoxide(Zr, Al, Ti, Si)

UF

silicon die

Source: www.wikipedia.org

Si

adhesive failure with residue on Si

Si

toughened epoxy (50μm)

0 20 40 60 80 100 120 140 160 18010-12

10-11

10-10

10-9

10-8

10-7

10-6

10-5

10-4

Cra

ck G

row

th R

ate,

da/

dt(m

/s)

Applied Strain Energy Release Rate, G(J/m2)

Hybrid Layer

5 min aged HL

20 min aged HL 1 min aged

HL

Si

Si

toughened epoxy

HL

Si

Si

HLtoughened epoxy

UF

silicon die

…environmental degradation of toughened UF epoxy, causing continued growth of interfacial defects even at very

low loads

Reliability Challenges with Packages and 3D Structures

Debonding and Fracture

• moisture, temperature and fatigue

• kinetic mechanisms and long-term reliability

Performance Bonding

• multiple substrates, 3D structures, embedded sensors, …

• hybrid layer optimization• single-step dual bonding/barrier layer

properties• deformation• fracture• fatigue…

Computational Modeling

• molecular structure and properties• new materials discovery

Adhesive Joints

H-bond

waterstrainedSi-O-Si bond

HybridsEpoxies

toughened epoxytoughened epoxy

Hybrid Layers for High-Performance Adhesion

UF

silicon die

Source: www.wikipedia.org

2 4 6 8 10 120

10

20

30

40

50

60

70

Crit

ical

Fra

ctur

e E

nerg

y, G

C (J

m-1)

Isoelectric Point

SiO2

TiO2

SnO2

Al2O3

NiOITO

BMG

tune parameters: sol-gel pH

compositionmetal atoms

surface catalysis

Substrate IEP Max Gc (J/m2)

WO3 0.2-0.5 ---

SiO2 1.7-3.5 57.4 ± 7.4

SnO2 4.5-5 33.6 ± 4.4

BMG 4.7 25.4 ± 2.4

TiO2 6 27.9 ± 3.6

Al2O3 7-8 21.9 ± 1.3

ITO 8.3 18.8 ± 1.1

NiO 10-11 11.4 ± 2.2sol p

H

Hybrid Layers for High-Performance Adhesion






C Si

H

Si

H

a-SiC:Hcrystalline SiC

C Si

Si

Si

Sireduced

connectivityfully connected

Hydrogenated Amorphous Silicon Carbide (a-SiC:H)

network backbone: Si-C, C=Cterminal groups: -H, -CH3

Si

CHCH3

Matsuda, King , Dauskardt, Acta Mat. 2011.

• chemical and thermal stability• unique opt-electrical properties

Si-O-Si bond free…• low sensitivity to moisture cracking• can exhibit high fracture resistance

PE-CVD at 400oCprecursors: methylsilane, phenylsilane, He, H2

stoichiometric (C/Si ~ 1)non-stoichiometric (C/Si ~ 5)

phenyl organic porogen

1.5 2.0 2.5 3.0 3.5 4.010-10

10-9

10-8

10-7

10-6

10-5

10-4

Cra

ck G

row

th V

eloc

ity, v

(m/s

)

Applied Strain Energy Release Rate, G (J/m2)

H2O

OSG 30%RH

OSG 80%RH

a-SiC:H20%RH

a-SiC:H70%RH


• chemical and thermal stability• unique opt-electrical properties

Si-O-Si bond free …(trace amounts)• low sensitivity to moisture cracking• can exhibit high fracture resistance

Hydrogenated Amorphous Silicon Carbide (a-SiC:H)

network backbone: Si-C, C=Cterminal groups: -H, -CH3

Si

CHCH3

1.5 2.0 2.5 3.0 3.5 4.00

2

4

6

8

10

12 Stoichiometric Non-stoichiometric

Frac

ture

Ene

rgy,

Gc (J

/m2 )

Average Coordination Number, m250 150 100 50 0 -50

PPM

SiC-I

C=C

CHx (-C-C-C-C-)

C-Si

SiC-H

200

C13 NMR

plasticity?

SiC-I(C/Si~5)

Cohesive Fracture Energy and Connectivity

stoichiometric

SiC-H(C/Si~5)


single crystal SiC

non-stoichiometric

0.0 0.2 0.4 0.6 0.8 1.0 1.20

2

4

6

8

10

12

Coh

esiv

e Fr

actu

re E

nerg

y,

Gc (J

/m2 )

sp3 CHx/Network Si-C bondsSi

Si

C Si

H

Si

H

SiC-I

sp3 CHx/Network Si-C bonds were characterized by FTIR, XRR, and RBS.

increasing porogen

plasticity

Plasticity in Non-Stoichiometric a-SiC:H Films

remaining sp3 carbon chains

a-SiC:H

phenyl organic porogen

Plasticity in Non-Stoichiometric a-SiC:H Films

0 2 4 6 8 10-500

-400

-300

-200

-100

0

100

Ver

tical

Dis

plac

emen

t, z

(nm

)

Horizontal Displacement, x (m)

SiC-Iload=3mgσYS=153MPa

SiC-Hload=5mgσYS=792MPa

pileup

nanoindentation

SiSi

SiC-I (plasticity)porogen → sp3 C chain → plasticity

Si C C Si

SiC-H (brittle)phenyl, C=C

0 500 1000 1500 2000 25000

3

6

9

12

15

Frac

ture

Ene

rgy,

Gc (J

/m2 )

Film Thickness, h(nm)

thickness dependence of Gc

SiC-H

SiC-I crack tip

plastic zone 2rp

215nm

3nm

I-SiCp2r

plasticity

Toughening with Ceramic-Like a-SiC:H Filmstoughening by metal films

limited metal plasticity at nanoscale

• low dislocation and mobility• small grain size (Hall‐Petch)

a‐SiC:H(25‐250 nm)

10-2 10-1 1 100

20

40

60

80

100

20

Copper Layer Thickness, h (m)In

terfa

ce F

ract

ure

Ene

rgy,

Gc

(J/m

2 )

Cu layer thickness300 Å - 16.4 m

substratedielectric glass

elasticmetal

(Lane, Dauskardt, 2000)

a‐SiC:H(25‐250 nm)

nanoporous hybrid glass

silicon substrate

SiCN (25 nm)

SiCN (25 nm)

GC = G0 + Gplasticity

thickness limit ~300 nm

Matsuda, Dauskardt et al., Small, 2012 in review.

Toughening with Ceramic-Like a-SiC:H Filmstoughening by polymer films

polymer plasticity at nanoscale

• limited thermal stability• incompatible deposition

a‐SiC:H(25‐250 nm)a‐SiC:H

(25‐250 nm)

nanoporous hybrid glass

silicon substrate

SiCN (25 nm)

SiCN (25 nm)


0 50 100 150 200 25002468

1012141618

Frac

ture

Ene

rgy,

Gc

(J.m

2 )Film Thickness, h (nm)

SiO2

SiCNGpl hpolymer

(Kearney, Dauskardt, 2004)


0 50 100 150 200 2500

1

2

3

4

5

6

7

Adh

esio

n en

ergy

, GC (J

m-2)

a-SiC:H film thickness, ha-SiC:H (nm)

Gpl

G0

much more effective toughening than metal films, more thermally stable than polymers

0 200 400 600 800 10000

4

8

12

16ys (MPa)

71 13 104 11 165 30430 45995 166

Adhe

sion

ene

rgy,

GC (J

m-2)

OSG thickness, hOSG (nm)

Gpl

nanoporous OSG

(100 nm)

a‐SiC:H(25‐250 nm)

SiCN

a‐SiC:H yield strength 71 ‐ 995 MPa

nanoporous OSG

(20 ‐ 1000 nm)

a‐SiC:H(250 nm)

SiCN

Toughening with Ceramic-Like a-SiC:H Films








Degradation and Reliability of PV Devices and Modules

Thermal cycling, mechanical stress, moisture, chemically active environmental species, and solar UV.

Uncertain degradation kinetics and reliability models.

Substrate

H2O, O2, H2other active chemical

species

photochemical reactions

cracking and debonding

UV Exposure

defect evolution in nanomaterial

layers

surface weathering

Substrate

H2O, O2, H2other active chemical

species

photochemical reactions

cracking and debonding

UV Exposure

defect evolution in nanomaterial

layers

surface weathering

Severe operating environments:

Roll-to-Roll Flexible Inverted Polymer Solar Cell• Manufacturing: automated R2R

- high throughput - large area

• Materials - abundant- cheap- light weight

• Flexible Substrates

Typical Inverted Polymer Solar Cell

polar groups

PEDOT:PSS hydrophilicP3HT:PCBM hydrophobic

flexible PETITO

PEDOT:PSSAg

P3HT:PCBMZnOZnO

poorcohesion

pooradhesion

0 20 40 60 80 1000.0

0.4

0.8

1.2

1.6

2.0

0.0

0.4

0.8

1.2

1.6

2.0 E

fficiency, E (%

)A

dhes

ion

Ene

rgy,

GC (J

/m2 )

Fraction PCBM in P3HT:PCBM (wt%)

Effect of BHJ Composition on Adhesion

S

P3HT

PCBM

Dupont, Oliver, Krebs, Dauskardt, Sol. Eng. Mat., 2011

Fullerene rich layers lead to very poor adhesion

• Heterojunction layer thickness– is cohesion in organic layers sensitive

to layer thickness?

• Composition of the heterojunction layer– limited bonding to fullerene– polymer/PCBM ratio makes stronger layer

• Molecular intercalation– manipulating the types of intermolecular

interactions

• Annealing– morphology of the BHJ layer

changes with annealing

P3HT PCBM Indene C60

Factors Effecting Cohesion of BHJ Layers

Standard 150°C 0.5h 150°C 2h

organic BHJelastic layer

elastic substrate

plastic zone

0

1

2

3

4

5

6

7

8

Frac

ture

Ene

rgy,

Gc (J

/m2 )

Effect of Molecular Intercalation on Cohesion

PQT-12

bis-PC71BMnon-intercalated cell

PC71BMintercalated cell

+

+

P3HT

PC60BM+

pBTTT-C14

PC71BMintercalated cell

+

bis-PC71BMnon-intercalated cell

+

Glass SubstrateITO

Al

BHJ LayerFailure in BHJ layer

1:1 poylmer to fullerene mass ratio

Barrier Films in Solar Modules

Source: Vitex Systems

Assessing UV and Environment on Debonding Kinetics

Po

Load

, PC

rack

Len

gth,

a

Time (s)

dP/dt

da/dt

automated load relaxation debond growth analysis

compliance analysis

Debonding Kineticsexplore role of:

• UV flux

• humidity, O2, OH, …

• temperature

• mechanical loading

test data

sensitivity to < 10-10 m/s

DTS Delaminator v8.2

Glass Substrate

ITO

ITO

Glass Substrate

Simulated UV Exposure

polysiloxanebarrier

0 1 2 3 4 5 6 710-11

10-10

10-9

10-8

10-7

10-6

10-5

10-4C

rack

Gro

wth

Rat

e, d

a/dt

(m/s

)

Strain Energy Release Rate, G (J/m2)

No UV0 mW/cm2

Ghv ~ 1.3 J/m2

Ghv ~ 0.8 J/m2

UV Exposure (3.4 eV)

UV intensity

UV Effects on Molecular Bond Rupture

1.2 mW/cm2

0.6 mW/cm2

NkT

INCGaKdtda Ehvn

HT 22sinh20

Backsheet and Encapsulant Debondingin Solar Modules

New Portable Full Panel Adhesion

Pa

0 1000 2000 3000

20

40

60

80

100

120

140

Load

(N)

Distance (um)

Square Cantilever Beam AdhesionAdhesion energy, Gc, depends on:

P (delamination force)E (young modulus of the square)

h (thickness of the square)

Back Side of Full Panel

Delaminator (v8.2) Adhesion Test System

DTS system and support: [email protected]

Ageing Temperature Effect on Debond Energy

20 30 40 50 60 70 80 900

200

400

600

800

1000

1200

Unaged

Deb

ond

Ene

rgy,

Gc (J

/m2 )

Ageing Temperature (°C)

Ageing time =1000 hrs

0 50 100 150 200 250 300 35010-8

10-7

10-6

10-5

Deb

ond

Gro

wth

Rat

e, d

a/dt

(m/s

)

Debond-Driving Force, G(J/m2)

Temperature Effect on Debond Kinetics

40°C

10°C20°C30°C

Debond Kinetics Model

Polyvinyl fluoride

Polyester

crp

Viscoelasticrelaxation

Arrhenius

Williams-Landel-Ferry (1955)

RH=40%

Outline• Molecular Modeling and Design of Hybrid Glasses





http://www.npr.org/blogs/health/2012/10/02/162159367/how-sunlight-weakens-your-skin

Biniek, Levi, Dauskardt, PNAS, Oct 1, 2012

Biological Hybrid Films and Treatments

mechanical behavior effects cosmetic aspects of skin

appearance, feel, and firmness…

Mechanical Function of Human Skin

Skin Care Forum

mechanical function and solar UV exposure, wound care,

biosensing, drug delivery, and scar formation…

Alza E-Trans ®

1 mmAlza Macroflux ®

Solar UV Effects on Biomechanical Functionclimate change increases incidence of UV exposure

hSC

Epidermal/DermalSubstrate

SC

SC

Cracking and Chapping

SC

Epidermal/DermalSubstrate

Buckling Instability

natural skinstress

undamaged skin

SC

Epidermis

Dermis

SC

skin

SC in tension SC in compression

Biomechanical Model for SC Damage

Solar UV Effects on Biomechanical Function

Control 160 8000.0

0.1

0.2

0.3

Frac

ture

Stra

in,

SC

Broadband UVB Dosage (J/cm2)

(strain to failure)

micro tension

Control 1.8 6.7 43 1600

1

2

3

4

5

6

7

Del

amin

atio

n E

nerg

y, G

C (J

/m2 )


abdomen

(corneocyte adhesion)

delamination

Broadband 311 nm UVB

Inte

nsity

(rel

)

Wavelength (nm)

UV Exposure

Solar UV Effects on Biomechanical Function

Carrier +

Sunscreenno UV

Carrier +

Sunscreen20 J/cm2

NB UVB

0

2

4

6

8

10

Del

amin

atio

n E

nerg

y, G

c (J

/m2 )

Carrier Only

20 J/cm2

NB UVB

UVB SunscreenCarrier (Phenethyl Benzoate)

+ Sunscreen (8% Padimate O)

UVB absorberEthylhexyl Dimethyl PABA

UV Exposure

sunscreen noneControl 1.8 6.7 43 160

0

1

2

3

4

5

6

7

Del

amin

atio

n E

nerg

y, G

C (J

/m2 )


abdomen

(corneocyte adhesion)

delamination

Skin Stresses and the Driving Force for Damage

~18% R.H. 25°C

0 2 4 6 8

0

1

2

3

~30% R.H.

~45% R.H.

SC

Stre

ss,

SC

(MP

a)

Time, t (h)

~33°C, 30% R.H. SC (~20 µm)

Glass Substrate

SC

In-Plane Bi-Axial Stress State

x

y

Levi, Weber, Do, Dauskardt, Int. J. Cos. Sci., 2010.

– wafer curvature technique for SC stresses– effects of treatment on stresses

SC

SCSC

EhZG

2

0 50 100 150 200 2500

1

2

3

4

5

no damageNor

mal

ized

Dam

age

Driv

ing

Forc

e, G

/GC


damage

surface cracking

channeling

Predicted UVB Effects on SC Damage

G ZSC

2 hSC

ESC

Biniek, Levi, Dauskardt, PNAS, 2012

Summary• Molecular Modeling and Design of Hybrids





Adhesion and Thermo-Mechanical Reliability in Emerging ...

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