session 15: measuring substrate-independent · 2016. 9. 4. · the solution: accounting for...

Session 15: Measuring Substrate-Independent

Young’s Modulus of Thin Films

Jennifer Hay

Factory Application Engineer

Nano-Scale Sciences Division

Agilent Technologies

[email protected]

To view previous sessions: https://agilenteseminar.webex.com/agilenteseminar/onstage/g.php?p=117&t=m

https://agilenteseminar.webex.com/agilenteseminar/onstage/g.php?p=117&t=m

What’s the problem?

• Low-k film (440

nm) on silicon

• Berkovich indenter

• CSM (1nm, 75 Hz)

• Oliver-Pharr

analysis

?

The solution: accounting for substrate influence

• Low-k film (440

nm) on silicon


• CSM (1nm, 75 Hz)

• Oliver-Pharr

analysis PLUS

thin-film analysis

Hay, J.L. and Crawford, B., "Measuring Substrate-Independent Modulus

of Thin Films," Journal of Materials Research 26(6), 2011.

“It was fun to read.” – Prof. Gang Feng, Villanova University

Both film and substrate influence measured

response

Development of strain field during nano-indentation of a film-substrate system, from Modelling

Simul. Mater. Sci. Eng. 12 (2004) 69–78. (Authors: Yo-Han Yoo, Woong Lee and Hyunho Shin)

Review of efforts to solve this problem

• (1986) Doerner and Nix: Analytic model assuming linear

transition from to substrate and including an empirically

determined constant.

• (1989) King: Form of Doerner-Nix model with no adjustable

parameters.

• (1989) Shield and Bogy: Analytic model, but with physical

problems.

• (1992) Gao, Chiu, and Lee: Simple approximate model.

• (1997) Mencik: Practical refinements to the Gao model.

• (1999-2006) Song, Pharr, and colleagues: Alternate version

of Gao’s approximate model.

The Song-Pharr model with Gao’s weight function

a

t film, mf

substrate, ms

mmm fsa

II11

)1(1

00

m ≡ shear modulus; E = 2m(1+n)

Modeling the relationship between two springs

Springs (of differing stiffness) in series,

subject to a force:

• The deformation in each spring is

DIFFERENT. The more compliant spring

deforms more.

• The MORE COMPLIANT spring dominates

the response.

Springs (of differing stiffness) in parallel,

subject to a force:

• The springs undergo the SAME

deformation.

• The STIFFER spring dominates the

response

How to account for lateral support of the film?

When film is stiff:

• Deformation in the top

layer of the substrate

approaches that of the film.

• Film dominates the

response.

clearly

series

Parallel

?

Allow film to act both in series and parallel (Hay & Crawford, 2011)

film

Indentation force

substrate

film

substrate film

Indentation force

previous form new form

But previous advancements are retained

• Gao’s weight functions, I0 & I1 for gradually shifting influence

of each spring with indentation depth.

• Mencik’s suggestion that t = t0 – hc.

• Definition of effective Poisson’s ratio suggested by Song and

Pharr.

A new model for elastic film-substrate response

film

substrate film

Applied indentation force

A new model for elastic film-substrate response

mf : shear modulus, film

ms : shear modulus, substrate

F : empirical constant;

F = 0.0626

a : contact radius

t : film thickness

D : relates stiffness to

modulus; D=4a/(1-na)

I0 : Gao’s weighting function;

as a/t → 0, I0 → 1;

as a/t → ∞, I0 → 0

force

Hay & Crawford, 2011

Solving for film modulus: mf = f(ma, mf, t0, a, hc, F)

Sneddon, 1965, as implemented by

Oliver and Pharr, 1992




Gao, et al., 1992






Gao, et al., 1992



Song & Pharr, 1999




Gao, et al., 1992



Song & Pharr, 1999

Gao, et al., 1992




Gao, et al., 1992

Menčίk et al., 1997



Song & Pharr, 1999

Gao, et al., 1992

The value of finite-element simulations

t Ef-in

70.3o

0

0.05

0.1

0.15

0.2

0 50 100 150 Lo

ad

on

Sam

ple

/mN

Displacement/nm

Eout Analytic

model


t Ef-in

70.3o

0

0.05

0.1

0.15

0.2

0 50 100 150 Lo

ad

on

Sam

ple

/mN

Displacement/nm

Eout

≡Eapparent

Sneddon


t Ef-in

70.3o

0

0.05

0.1

0.15

0.2

0 50 100 150 Lo

ad

on

Sam

ple

/mN

Displacement/nm

Eout

≡Efilm

Sneddon &

Hay-Crawford

Summary of 70 finite-element simulations (2D)

.

Simulation Es, GPa Maximum indenter displacement (h), nm

1-10 100 20 40 60 80 100 120 140 160 166 174

11-20 50 20 40 60 80 100 120 140 160 166 184

21-30 20 20 40 60 80 100 120 140 160 180 200

31-40 10 20 40 60 80 100 120 140 160 180 200

41-50 5 20 40 60 80 100 120 140 160 180 200

51-60 2 20 40 60 80 100 120 140 160 180 200

61-70 1 20 40 60 80 100 120 140 160 180 200

500 nm Ef = 10GPa

70.3o

Is everything OK with simulations?

0

2

4

6

8

10

12

14

16

18

20

0 10 20 30 40

Yo

un

g's

Mo

du

lus

[G

Pa

]

Indenter Penetration / Film Thickness [%]

Ef=Es, apparent

input film modulus for all simulations

Is everything OK with simulations?

0

2

4

6

8

10

12

14

16

18

20

0 10 20 30 40

Yo

un

g's

Mo

du

lus

[G

Pa

]


Ef=Es, apparent

Ef=Es, film alone



.


1-10 100 20 40 60 80 100 120 140 160 166 174

11-20 50 20 40 60 80 100 120 140 160 166 184

21-30 20 20 40 60 80 100 120 140 160 180 200

31-40 10 20 40 60 80 100 120 140 160 180 200

41-50 5 20 40 60 80 100 120 140 160 180 200

51-60 2 20 40 60 80 100 120 140 160 180 200

61-70 1 20 40 60 80 100 120 140 160 180 200

500 nm Ef = 10GPa

70.3o

Simulations: Compliant film on stiff substrate

.

0

2

4

6

8

10

12

14

16

18

20

0 10 20 30 40

Yo

un

g's

Mo

du

lus

[G

Pa

]


Ef/Es = 0.1, apparent



.

0

2

4

6

8

10

12

14

16

18

20

0 10 20 30 40

Yo

un

g's

Mo

du

lus

[G

Pa

]



Ef/Es = 0.1, film alone



.

0

2

4

6

8

10

12

14

16

18

20

0 10 20 30 40

Yo

un

g's

Mo

du

lus

[G

Pa

]



Ef/Es = 0.1, Film (Hay)

Ef/Es = 0.1, Film (Song-Pharr)



.


1-10 100 20 40 60 80 100 120 140 160 166 174

11-20 50 20 40 60 80 100 120 140 160 166 184

21-30 20 20 40 60 80 100 120 140 160 180 200

31-40 10 20 40 60 80 100 120 140 160 180 200

41-50 5 20 40 60 80 100 120 140 160 180 200

51-60 2 20 40 60 80 100 120 140 160 180 200

61-70 1 20 40 60 80 100 120 140 160 180 200

500 nm Ef = 10GPa

70.3o

Simulations: Stiff film on compliant substrate

.

0

2

4

6

8

10

12

14

16

18

20

0 10 20 30 40

Yo

un

g's

Mo

du

lus

[G

Pa

]


Ef/Es = 10, apparent



.

0

2

4

6

8

10

12

14

16

18

20

0 10 20 30 40

Yo

un

g's

Mo

du

lus

[G

Pa

]



Ef/Es = 10, Film (Hay)



.

0

2

4

6

8

10

12

14

16

18

20

0 10 20 30 40

Yo

un

g's

Mo

du

lus

[G

Pa

]



Ef/Es = 10, Film (Hay)

Ef/Es = 10, Film (Song-Pharr)


Determining the value of F (fudge factor)

. Ef-out (P, h)

Ef = 2mf(1-nf)

Ef-in

0

/

:

70

1

2

dF

EEEd

Fi

infinfoutf i

F was determined as that value which minimized the sum of

the squared relative differences (between output and input

film moduli) over all 70 simulations.

F = 0.0626

sim




Gao, et al., 1992

Menčίk et al., 1997



Song & Pharr, 1999

Gao, et al., 1992

NanoSuite integration in CSM “thin film” methods

NanoSuite integration in ET “thin film” methods

Application: SiC on Si wafers

Sample ID Description t

nm

16 Silicon carbide (SiC) on Si 150

17 Silicon carbide (SiC) on Si 300

Experimental method

• Materials:

o A set of 2 SiC films on Si

• Platform: Agilent G200 NanoIndenter with

o DCM head

o CSM option

o Berkovich indenter

o New test method: “G-Series DCM CSM Hardness,

Modulus for Thin Films.msm”

Stiff films on compliant substrates: SiC on Si

0

50

100

150

200

250

300

350

400

0 10 20 30 40 50

Yo

un

g's

Mo

du

lus

[G

Pa]


t=150nm, apparent

citation of results


0

50

100

150

200

250

300

350

400

0 10 20 30 40 50

Yo

un

g's

Mo

du

lus

[G

Pa]


t=150nm, apparent

t=150nm, film

citation of results


0

50

100

150

200

250

300

350

400

0 10 20 30 40 50

Yo

un

g's

Mo

du

lus

[G

Pa]


t=150nm, apparent

t=150nm, film

t=300nm, apparent

citation of results


0

50

100

150

200

250

300

350

400

0 10 20 30 40 50

Yo

un

g's

Mo

du

lus

[G

Pa]


t=150nm, apparent

t=150nm, film

t=300nm, apparent

t=300nm, film

citation of results

SiC on Si: Modulus at h/t = 20%

0

50

100

150

200

250

300

350

400

SiC on Si (t=150nm) SiC on Si (t=300nm)

Yo

un

g's

mo

du

lus

, h

/t=

20

%

[GP

a]

Sample

Film

Apparent

Film modulus is about 25% higher than apparent modulus!

t0 = 445 nm t0 = 1007 nm

“Rapid Mechanical Characterization of low-k Films,”

http://cp.literature.agilent.com/litweb/pdf/5991-0694EN.pdf

Application: low-k materials (on silicon)

Experimental method

• Materials:

o Two low-k films on Si

• Platform: Agilent G200 NanoIndenter with

o DCM head

o CSM option

o Express Test option

o Berkovich indenter

• Test Methods:

o G-Series DCM CSM Hardness, Modulus for Thin

Films

o Express Test for Thin Films

Modulus of low-k film (t = 1mm) is 4.44±0.08GPa

Hardness of low-k film (t = 1mm) is 0.70±0.02GPa

Application: Ultra-thin films

Four samples

Substrate: sintered Al2O3 and TiC

Basecoat: sputter-deposited Al2O3

(2600nm)

Four samples

Substrate: sintered Al2O3 and TiC

Basecoat: sputter-deposited Al2O3

(2600nm)

PECVD SiO2 (50nm) OR ALD Al2O3 (50nm)

• Agilent G200 with DCM II head and NanoVision

• Express Test


• Thin-film model applied to both basecoat and top layers.

Experimental method

Substrate – independent

modulus of 50nm films

E = 146 GPa

Application note: http://cp.literature.agilent.com/litweb/pdf/5991-4077EN.pdf

In summary, the proposed model…

• Has been verified by simulation and experiment.

• Is an improvement over prior models, because it works

well whether the film is more compliant or more stiff

than the substrate.

• Decreases experimental uncertainty by allowing

measurements to be made at larger depths which would

otherwise be unduly affected by substrate influence.

Application: Mechanical characterization of SAC

305 Solder by Instrumented Indentation Wednesday, May 14, 2014, 11:00 (New York)

Abstract The reliability of soldered connections in electronic packaging depends on

mechanical integrity; mechanical failure can cause electrical failure. Mechanical

integrity, in turn, depends on mechanical properties. In this presentation, we focus

on the SAC 305 solder alloy (96.5% tin, 3% silver, and 0.5% copper) due to its

prevalent utilization in electronic packaging. First, we demonstrate the use of

nanoindentation to measure the elastic and creep properties of SAC 305. Next, we

utilize an advanced form of nanoindentation to quantitatively map mechanical

properties of all the components of a realistic SAC 305 solder joint.

To register:



Session 16: Best Practice for Instrumented

Indentation Wednesday, June 11, 2014, 11:00 (New York)

Abstract The purpose of this presentation is to provide a practical reference guide for

instrumented indentation testing. Emphasis is placed on the better-developed

measurement techniques and the procedures and calibrations required to obtain

accurate and meaningful measurements.

Recommended Reading Hay J.L. and Pharr G.M., “Instrumented Indentation Testing,” ASM Handbook:

Mechanical Testing and Evaluation, Volume 8, pp. 232-243 (2000).

To register: https://agilenteseminar.webex.com/agilenteseminar/onstage/g.php?p=117&t=m


Thank you!

Two (sort of) independent problems

• Composite compliance: Substrate influences the

stiffness that is measured.

• Errant contact area: Common model for

determining contact area is strained in its

application to thin films.

These two problems are easily convoluted,

because they both tend to push the calculated

Young’s modulus in the same direction.

session 15: measuring substrate-independent · 2016. 9. 4. · the solution: accounting for...

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