PossibleStrategytowardaDesignSchemetoAvoidCatastrophic Failure
inInterconnectStructures underChipPackageInteraction
ShojiKamiya
DepartmentofMechanicalEngineering
NagoyaInstituteofTechnology
MasakiOmiya,NobuyukiShishido,Tomoji Nakamura
Let'sevaluatetheriskofCPIcracking,andtakeactionsaccordingly!!
May30th,2016
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(preseted in2014bySubi Kengeri,VicePresident,GlobalFoundries)
(complicated,becauseithappens,notalways,justoccasionally...matterofprobability?)
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Where's theorigin?Howdoesfailurepropagate?
Thesearethequestions.
HowmuchtoughnessGc ?
Howlonginitialcracksa ?
Dangerous!!
Insulator(low-k)
->Softandweak
Softerlow-kresultsinmuch
severer deformationand
thusstress concentration
attheinterfacecorner
SevererstressatthecornerofCuline/caplayerinterface,likelytheorigin.Then.....
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Specimenfabrication(ex.1um-squarespecimen)
Damasceneinterconnectstructure
Fracture testwithnanoindenterunderSEMobservation
Debonding
Stylus
Specimen
Interface
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Crackextension
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Experiment
Load (µN)
APPARENT ADHESION: common elastic calculation
for "CRITICAL ENERGY RELEASE RATE Gc"
Displacement (nm)
Load (µN)
Simulation
GC (J/m2)
Load
*assumingelasticdeformation
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Crack extension area (µm2)
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TRUE ADHESION: remove the effect of plasticity
for "INTERFACE ADHESION ENERGY Gi"
Plasticstrain
…
F2
20µm Cu line
δ1
F1
energydissipatedfor
plasticdeformation,
i.e.,
cracktipshieldedwith
plasticdeformation
δ2
Interfaceadhesionenergy
1
Gi = ∫ Fn dδ n
A
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Fn :Nodalforcebeforetwonodesarereleased
δn :Mutualdisplacement ofreleasedtwonodes
A:Newcrackextensionarea
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Scale dependent behavior of adhesion strength
Likelyahuge
overestimation!
Gc
Gi
~mm
数mm
Notch
"Nanotech syndrome"
Small is dangerous !
Huge relative range
of distribution
Stressrelaxationwithplasticity
Gi better ?
Risk(probability)offracture
Stress
Averageleveloftrueadhesion?
Strength
7
Strength and microstructure of copper line
- pathologyforthenanotechsyndrome
Adhesionstrengthmaydivergedependingoncrystalorientations...
Gi
Largerscatterinstrength
5µmsquare
~mm
mm
Likelyahuge
overestimation!
Gc
Notch
"Nanotech syndrome"
Small is dangerous !
Huge relative scatter
in submicron scale
Stressrelaxationwithplasticity
1µmsquare
Gi better ?
Averageleveloftrueadhesion ?
300nmsquare
ND
111
200nmcylinder
001
101
Then,thereisastrategywithsystematicevaluationforthedistribution...
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Trial toevaluateadhesionenergyonspecificorientations
CrystalOrientationIntegratedWorkof
Interface SeparationEstimationRoutine
COIWISER
nowbeingdeveloped
FirsttrialwithsinglecrystalCublank
intwoloadingdirections
2013/10/09
ADMETA-plus2013,Tokyo,Japan
Slipdirection
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Singlegrain
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(1μm square)
Averageandrange
bothenhanced
maxGi andhighestσy
minGi andlowestσy
AdhesionstrengthGc [J/m2]
EstimationfortheRANGEofapparentadhesion strength
Stressconcentrationeffect
fromgrainboundaries
with
largerGi andsmallerσy
evaluatedinLSI
Twinboundary
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Junction
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NowaimingatestimationforstrengthdistributionwithGBs
Estimated fracture load with different conditions
Obtain fundamental adhesion energy
* unique adhesion energy assumed
Further estimation of adhesion strength
over arbitrary combinations of grains
Combinatorial analysis for local strength
according to grain structures
2013/10/09
ADMETA-plus2013,Tokyo,Japan
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Summaryofproposalforpossiblestandardizationtowardfractureriskbaseddesignscheme
Design
(Fabless)
Packagingservice
Commonlanguagesfordeviceproduction
TCAD
•Deviceperformance
•Stressevolution
DESIGNRULES
necessary forCPIrisk,for
assessment andagreement
to be standardized ?
Chipfoundry
for another common language
Risk(yield)-basedengineering!
StartingwithTEGformechanics(withwiderlines?)
Diamond
stylus
anotherplug-in
Probabilityoffracture
underpackagingstress
σap
Risk(probability)offracture
Load
&
Stress
Strength
Specimen
σy
Gi
Grainorientation
(ofthecrystal) (ofacertainorientation)
statistics
Theseareprocessdependentparameters.
Localstrengthdistribution
fromalimitednumber
ofmeasurement
Wearelookingforcollaboration partners toexaminethiskindofpossibility !
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Demonstrationofcrackarrest-extensionsimulation ininterconnectstructures
Numerical simulation: 8x8 WL-CSP model
Chip:460 µm
300µm
Underfill:90µm
SolderBump:380µm
300µm
SolderPad:50µm
PCB:1 mm
CalculationmodelofWaferLevelChipScalePackage(WL-CSP).Thedieis8mmx8mmandattached
onPrintedCircuitBoard(PCB)by8x8solderbumps.Multi-levelsubmodelingtechniques wereused.
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Crack propagation simulation
•
•
•
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Numericalmodelforcrackpropagationanalysisoffour-layer
interconnectstructure.
StressconcentrationoccursatthecornerofCu/Capinterface.
InitialcrackisintroducedatthecornerofCu/Capinterface.
(Linewidth--- M1,M2:120nm,M3:240nm,M4:360nm)
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Crack propagation simulation
Howstrongthispointisisthematterofprobability.
Whenappliedstressislarger, or it'sweakerasamatterofprobability...
Crackingstopswithinlow-kwhentheinterfaceistoughortheloadissmall.
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Crack propagation simulation
Cu/CapisthefinalfortressagainstcatastrophicCPIcracking
CrackextendsunstablyonceCu/Capinterface isfullydelaminated.
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Scenario for catastrophic failure
Thermal
stress
Chip
Solder
Ball
Unstable extension !
ΔT=130 K
Temperature decrease
(Load increase)
(Time lapse)
PCB
Global failure!!
ΔT=110 K
Yield can be estimated !
Local
failure
ΔT=85 K
Crack arrested !
fromtheinformationofstrength-defect distribution
(2J/m2 supposed)
Cu via corner
May30th,2016
Cu line
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PossibleStrategytowardaDesignSchemetoAvoidCatastrophic
FailureinInterconnectStructuresunderChipPackageInteraction
ShojiKamiya
Department of mechanical engineering, Nagoya Institute of Technology
Stillhavealottoexamine.
Wearelookingforcollaboration partners toestablish thiskindofconcept!
incollaborationwith
Nobuyuki Shishido1, Kozo Koiwa1, Hisashi Sato1, Masaki Omiya2, Chen Chuangton1,
Masahiro Nishida1, Takashi Suzuki3, Tomoji Nakamura3, Takeshi Nokuo4, Toshiaki Suzuki 4
1 Nagoya Institute of Technology, Japan
2 Keio University, Japan
3 Fujitsu Laboratories Ltd., Japan
4 JEOL Ltd., Japan
N.I.T.
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