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Breakout session 1:CHARACTERIZATION AND MEASUREMENT

Fraunhofer IZFP-DMaria-Reiche-Straße 2D-01109 DresdenGermany

www.izfp-d.fraunhofer.dewww.nanoanalysis.fraunhofer.de

SEMATECH Workshop on Stress Management for 3D ICs using TSVs, Albany/NY, 03/16/2010, Breakout Session 1

Ehrenfried Zschech

http://www.izfp-d.fraunhofer.de/

http://www.nanoanalysis.fraunhofer.de/

Materials DATA, TECHNIQUES and VALIDATION

Does the proposed DFM methodology and flow make sense for stress management (for 3D IC integration in particular and advanced products in general)?

Which DATA is needed, what needs to be measured?

Which characterization and measurement TECHNIQUES do we need? Do we need other / modified measurement techniques?

What VALIDATION is required, and what kind of test structures is needed?

SEMATECH Workshop on Stress Management for 3D ICs using TSVs, Albany/NY, 03/16/2010, Beakout Session 1 - Ehrenfried Zschech

Stress engineering for 3D TSV-based technology *

Chip Performanceo FET stress engineering vs. 3D IC integration impact (wafer

thinning to some 10 µm, metal TSV, metal micro-bumps, …)o Effect of package-induced stress on transistor-to-transistor

performance variation through variation in carrier mobility and threshold voltage (effect on device characteristics)

o Stress effect on leakage and power

Reliabilityo 3D thermal and stress effects in electromigration and stress

migrationo ILD/IMD cracking, delamination, etc.

* Particular integration scheme: “via-middle” (particularly sensitive to mechanical stress)


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DFM simulation flow

Package-scaleFEM TOOL

OUTPUT 1:Displacements or distributed load on chip

faces

OUTPUT 2: Distribution of strain components across silicon at a device layer

Interconnect model 1: Smear interconnect layer with effective elastic properties

Interconnect model 2: Interconnect layer with layout-dependent elastic properties (compact)

Chip-scale FEM TOOL

Stress “relaxation” – redistribution across device layer due to its composite nature: initial strain

calculated for Si layer needs to relax (compact)

(V. Sukharev, Mentor Graphics)


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Simulation Flow: Package-scale - CPI (Example)

Materials properties needed for simulations(V. Sukharev, Mentor Graphics)

Package/d materials

Mech. Data Material and info requirements

Package substrate E-module(T), Bulk-CTE(T)

Un-assembled PCB

FC-solder Visco-plasticity,E-module(T)

Solder paste/ solder bars

Package solder Visco-plasticity,E-module(T)

Solder paste/ solder bars

Underfiller (FC-level)

E-module(T), Bulk-CTE(T)

Uncured polymer

Underfiller (µ-Bump)

E-module(T) , Bulk-CTE(T)

Uncured polymer

On-chip Cu interconnects

E-module at RT and elevated T,Thin film CTE

Bare chip, layout

Low-k material E-module at RT and elevated T,Thin film CTE

Bare chip, layout

Kuo-Chin Chang, et al. TSMC, Yuan Li, Altera


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Materials for assembly and packaging

Materials Functionality Chemical Compositions

Materials properties Measurement techniques

Interposer(organic PCB)

Chip carrier and electr.

redistribution

Composit of epoxy polymerand glass fibers

E=f(T,t)CTE=f(T)

Poisson=f(T)

DMA, bending testTMA, image correlation

Molding compound

Chip encapsulation,

protector

Ceramics-filled epoxy polymer

E=f(T,t), K=(T,t)CTE=f(T)

Poisson=f(T)microstructure

DMA, tensile tests, compression testTMA, image correlation

ultra sonic transmission microscopy

Solder ballsElectrical and mechanical connection

Sn-rich alloy(SnAg3.5,

SnAgCuAyBz)

E=f(T)visco-plasticity

CTE=f(T)Poisson=f(T)

microstructure

Nanoindentationmicro shear tester, tensile tester,

image correlationultra sonic transmission microscopy

FIB-SEM, EBSD

Cu pillarsElectrical and mechanical connection

Electroplated Cu

E=f(T), PlasticityCTE=f(T)

Poisson=f(T)microstructure

nanoindentation, tensile testsImage correlation

ultra sonic transmission microscopyFIB/SEM, EBSD

UnderfillerMechanical

stabilization of joints

Epoxy resin(filled & unfilled)

E=f(T,t), K=(T,t)CTE=f(T)

DMA, tensile tests, compression testTMA, image correlation


Materials for wafer-level process

Materials FunctionalityChemical

Compositions

Materials properties Measurement techniques

Tungsten,Copper

Electrical wiring W, Cu, Cu alloy

E, vCTEstrain

grain size, texture

Nanoindentation, AFAMX-ray reflectometryX-Ray diffraction

Blanket films: XRD, Patterned structures: OIM (SEM, TEM)

ILD: SiO2, low-k, ULK

InsulationSiO2-based,

FSG, low-k, ULK (SiCOH)

E, vCTE

adhesion

Nanoindentation, scratch testAFAM/FM-AFM, UFM

X-ray reflectometry4-point bending, DCB

Ellipsometry, TEM-EELS

Silicide Contact NiSix, NiSixAyE, vCTE

Nanoindentation, AFAM/FM-AFMX-ray reflectometry

Ultra sonic transmission microscopy

Stress liner Stress in channel SiNx

E, vCTEstrain

NanoindentationX-ray reflectometry

Blanket films: Wafer curvature

Passivation Adhesion, etch stop, barrier SiNxCy, SiNx

E, vCTE

NanoindentationX-ray reflectometry

Si channel FET channel Si (in future Ge, III-V ?) strain TEM (ENBD, DFEH), nanoRaman


Characterization techniques for (thermo-)mechanicalmaterials parameters – Examples ! -

Materials parameter(selection)

Technique Availability

E nanoindentation, FM-AFM/AFAM

yes

v modifiednanoindentation

yes

CTE XRR, optical image correlation, …

yes

Channel strain TEM (ENBD *, DFEH **, …), nanoRaman, …

yes, nanoRamanresolution ~ 100nm

ENBD: Electron Nano Beam Diffraction – H. J. Engelmann et al., 4th EMC Proc. 2, 13-14 (2008)

DFEH (HoloDark): Dark Field Electron Holography - M. Hytch et al., IEEE IEDM Dig. 2.5 (2009)


Multi-scale materials characterization

Stress management in complex systems (packaged dies, 3D integration, etc.) require multi-scale modeling and MULTI-SCALE CHARACTERIZATION.

Local materials modifications require MULTI-SCALE CHARACTERIZATION.

Example: Low-k/ultra low-k dielectrics1) E in IMDx in dense OSG2) E in UV-cured porous OSG

Analytical TECHNIQUES with different spatial resolution are needed.


Multi-scale materials characterization


Thin Films Surface

Interface

Gradients

Patterned Shrinking Multilayer

Elastic Modulus

Adhesion + Cohesion

Sub-Critical Debond

Fracture Toughness

CTE

Microstructure

…Bonds

nm

Å

Courtesy: Holm Geisler, Globalfoundries, Dresden, Germany

Nanoindentation technique


… a useful tool to measure elastic and plastic properties of materials

24.56 r cdPS E hdh

β= =

Reduced Elastic Modulus

maxPHA

=

Hardness

For homogeneous materials:

Oliver and Pharr

Cube corner nanoindentation in organosilicate glass (OSG): Before and after UV curing

5min monochromatic UV curing


Measurement: KB Yeap, Y. Ritz, Fraunhofer IZFP-D, supported by U. Hangen, Hysitron Inc.

Nanoindentation and SPM-based techniques


For homogeneous materials:

… a useful tool to measure elastic and plastic properties of materials, however critical for regions < 100 nm

For heterogeneous materials:

Measurement of mechanical properties in sub-100nm regions

T

Backbone + Pores

• Plasma damage

• UV cure

SPM-based techniques


Mapping elastic properties of Cu/OSG stacks using X-section FM-AFM

Local differenceson small scales

Blue: compliant

Green: medium

Brown: stiff

• Different OSG layers have different elastic modulus (Er) values

• All OSG layers except M1 show 10…20nm zones with higher modulus next to etched structures (modulus gradient)

• Possible explanation for differences: differences in etch/clean processes or stress (?)

Er/

E0

Y- Position [a.u.]

M1 M2 M3 M4 M6 M7


E. Zschech, D. Chumakov, P. Potapov, H. Geisler, H. J. Engelmann, AIP Conf. Proc. 945, 142-151 (2007)

FM-AFM analysis: Er modulations due to monochromatic UV curing


Topography image

FM image

Topography image

FM image

film

T. S. Kim, D. Chumakov, E. Zschech, R. Dauskardt. JAP 103, 064108 (2008)

New UV curing interference model

Superposition of the effects of standing waves in the shrinking film over time

SiOSG

SiSiCN (95 nm)

UV RADIATION

glass

SiSiCN (95 nm)

UV RADIATION

glass (18% shrinkage)

with absorption (assumed linear)

without absorption

0 100 200 300 400

Cure

Pro

file

Thro

ugh F

ilm

Predicted cure profile from standing wave

Distance from Bottom of glass film, z (nm)


T. S. Kim, D. Chumakov, E. Zschech, R. Dauskardt. APL 95, 071902 (2009)

Validation/Calibration

Electrical measurements: Ion, Vt, etc.o Fast & accurate measurementso Specially designed test-chip is needed – expensive & time consumingo Stress variation is not responsible for total variation in electrical characteristics. Other sources of variability should be accounted:- sub-wavelength lithography- random dopant fluctuation- temperature fluctuation, etc.

Strain measurements inside transistor channelo Direct but time consuming measurementso No need in test chip

see next slides


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MOSFET cross-sections

NMOS PMOS

SiGeStress Memory

NiSi

electrons tensile holes compressive

SEMATECH Workshop on Stress Management for 3D ICs using TSVs, Albany/NY, 03/16/2010, Beakout Session 1 - Ehrenfried Zschech20

TEM diffraction techniques

Parallel Beam Convergent Beam


C2 Aperture

Sample

Objective Plane

Back Focal Plane

CBED Nano Beam Diffraction

Small convergence0.4 -1.2 mradBeam size: 6-10nm

SAD

[110]

high convergence

α-1 1-1

0 0 0

-2 2 0

almost parallel

High convergence

NBD: Strain in the MOSFET channel


latti

ce p

aram

eter

(a·2

½) -

[110

] [Å

]

Measuring spot

unstrained

unstrained

NBD results agreewell with Ramanresults

good reproducibility:strain values within~ ±0.15 %transistor channel region shows

clearly compressive strain

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H. J. Engelmann, H. Geisler, R. Huebner, P. Potapov, D. Utess, E. Zschech, 4th EMC 2008, Proc. 2, 13-14 (2008)

Acknowledgement

Fraunhofer Institute for Nondestructive Testing, IZFP-D, Dresdeno Mike Rölligo Kong-Bong Yeapo Rene Hübnero Yvonne Ritz

Fraunhofer Institute for Reliability and Microintegration, IZM-ASSID, Dresdeno Jürgen Grafe

GLOBALFOUNDRIES Inc., Dresdeno Hans-Jürgen Engelmanno Holm Geislero Dmytro Chumakov


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