limitations to miniaturization of magnetic components€¦ · • magnetic component (inductor) –...

LimitationstoMiniaturizationofMagneticComponents

EyalAklimi,Ph.D.May2017

EyalAklimi,2017

Outline

•Background:WhyMiniaturizePowerElectronics?•FromDiscretetoIntegratedInductors• Fabrication• Structures• Limitations• Comparison

•AdvanceTopicsandInnovativeReports

EyalAklimi,2017

ImproveEnergyEfficiencythroughMiniaturization

• Efficiency isgainingincreasedinterestasmoreelectronicsrunoffofindispensablesources(batteries)andhigh-conversionratioasDCmicrogrids emerge.

D.Nenni,2011

Size∝ Speed

• MakingDC-DCconverterssmaller,faster,moreefficient,andwithhigherconversionratioiskeytoachievingmanydesirableimprovementstoelectronics:• DeeperPDNreducesI2Rlosses,volume,weight,andheatdissipationmanagementrequirements• Techniquesthatrequirebetterconverters:DVS|Cycleandterminatepower|Fasterresponse|Sub-threshold

• Therearesimilaritiesbetweenultra-lowpowersystemsandvery-highpowersystems

EyalAklimi,2017

MiniaturizingDC-DCConverters

POL

PSiP/PMIC

IVR

EricssonBMR450

AlteraEN5364QI

E.Burton,etal.,APEC2015

SizeTrend|I/Ocount

EyalAklimi,2017

MiniaturizingDC-DCConverters- Terminology

• Integratedvoltageregulator(IVR)bringsthelaststageofvoltageconversionintoICpackage• FullyIVR(FIVR)referstomonolithicintegration,whereconverterswitchesareimplementedusingsametransistorsasloadIC• Pros:easyintegration,significantlyreducedinterconnectsparasitics

• Cons:limitedtolowinputvoltagesascorevoltagesdecrease

EyalAklimi,2017

Miniaturizing DC-DCConverters

Whatpreventsswitchingpowersuppliesfromshrinking(POL→ IVR)?• ThreemajorelementsofSMPS(inorderlarge→ small):

• Magneticcomponent(inductor)– biggestchallenge• Switches• Controller,switchesgatedrivers

• Lossesandsizeareintertwinedthroughswitchingfrequency:• Smallerswitches→ higherconductionlosses• Largerswitches→ higherswitchinglosses

𝐿$%&,($% ∝ 1 𝑓+,

Copperalsomatters,ofcourse

• Highfrequencyisoftenlimitedbyinterconnectsparasitics,which,constantlygetsbetter(lower)withbetterintegration

DiscretePackage-integratedChip-integrated

Control

POL/PSiP/PMIC

Integrated

DeadZone

D.W.Lee,2008

EyalAklimi,2017

• Inductorsrequirecurrentcarryingwinding (typicallycopper),and:• Nocore (“aircore”)• Highpermeabilitycore (yoke)

DiscreteandIntegratedMagneticComponents

Integrated(andmicro-magnetic)

Coilcraft,2014

D.Harburg,2012

K.L.Shepard,2012

P.McCloskey,2014

Vishay,2017

Discrete

EyalAklimi,2017

MagneticCoreinInductors

• Themotivationforaddinghigherpermeabilitysoftmagneticmaterialcore,istoincreaseinductancedensity;magneticfluxishowinductorsstoreenergy(comparetocapacitorsthatstorecharge)andhigherflux→ higherenergystoragecapacity• Thecoreprovideslowreluctancepath(“concentration”)forthemagneticflux

AMI,2017

• 𝐵 ∝ 𝜇/𝐻 magneticfieldisamplifiedbythecoretohigherlevelsofmagnetizationflux

EyalAklimi,2017

• Largesizemicroelectronicsmethodologies,usinghardmaterials

• Sputtering:veryslow,difficulttopattern/etch

• Multipleoptions(outsidethescopeofthistalk)

• Materials:solid,powderedmetals,etc.• Techniques:machining,sintering,laminationpressing

FabricationComparison

• windingcopperwire:aroundbobbin/core,orselfsupported

• Sizelimited,Mustbeabletoswivel• Serialproduction

• SameasBEOL:fabricationinlayers,patterningbylithography,withvias/spacers

• SizeandvolumelimitedCopp

erWire-wound Planar

DiscretecomponentCo

ilcraft,201

4

J.–B

.Yoo

n,200

2

Integratedcomponent

FabricationStructuresLimitationsComparison

Magne

tics

• Electroplating:Throughmask/PR

• Chipconscious!

D.S.Gardner,2010

EyalAklimi,2017

Micro-MagneticComponentsStructures

Pseudo-planar(layered)integratedinductorstructures• Spiralair-core(uselessforpowerapplications),orsingle/veryfewturns

• Cladded (race-track)usuallyelongated;multiturnsorsingle(alsostripline,orslab)

• Solenoid (toroidal)• Meander

D.W.Lee,2008

F.Zhang,2008

B.Estibals,2005

E.A.Burton,2014

N.Wang,2012E.Aklimi,2016

J.Kim,2015


EyalAklimi,2017

MajorIntegratedMagneticsLimitations

Coppercross-sectionissmall→ highinductorresistance (ESR)Solutions:• Depositasthickaspossiblecopper• Designveryfewturns:

• Copperresistance𝐸𝑆𝑅 ∝ 𝑁 (numberofturns)andinductance𝐿 ∝ 𝑁5 soitisvery temptingtodesignmoreturns

• Significantcopperlossesareusuallynotacceptable.Exceptions:• Onehigh-conversion-ratioconverterreplacesmany2:1converters• Ifefficiencyinlessofapriority


Mostlimitationsarenotuniquetointegratedmagnetics,butsomeareratheracute

EyalAklimi,2017


Smallcoressaturatefastatlowcurrents(=permeabilitynon-linearity)

Solutions:• Depositthickmagneticcores.Butstill,itisverydifficulttogoaboveafew𝜇𝑚• Electroplatingisinferiorbutgivesgoodrates• Sputterdepositionisveryslow(@0.1Å/𝑠𝑒𝑐,each1𝜇𝑚 takes±28hours)

• Designveryfewturnstoreducemagneticflux• Lowinductance

BiasCurrent(mA)

COMSOL,2013

E.Aklimi,2016Frequency[Hz]

Indu

ctance[H

]


EyalAklimi,2017


Solutions:• Increaseelectricbulkresistivity(SputteredCoZrTa 100µΩ-cm,ElectroplatedCoWP >100µΩ-cm),versuslowresistivityNiFe 45µΩ-cm

R.Clarke,2008

Eddycurrentsgiverisetosignificantlossesathighfrequency,andskin-effect

• Laminate• Cannotelectroplatelaminations.Mustsputter-deposit:layersarethin

• laminatewiththickness≅ skindepth• Decreasefrequency

• Higherinductanceisneeded


EyalAklimi,2017


Otherchallenges:• Hysteresislossofmagneticyoke∝ 𝑓• Integratedinductorsareverythin,typically100’sof𝜇𝑚laterallybutonlyafew𝜇𝑚 thick

• Difficultyclosingmagneticlooplaterallywithsmallstructures• Solution:add2nd magneticlayer(claddedstructure)

• Analyticalinductorsdesignformulasandexpressionsvarytoomuchfromactualbehavior.Requires:• Simulationstoestimateinductorparametersandbehavior• Fabricatinginductorscatalogandfitmodelsparametersusingmeasurementresults

R.Clarke,2008

𝐿 =𝜇𝑁5𝐴𝑙

Topview Cross-section

D.W.Lee,2008


EyalAklimi,2017


Gainsfromaddingmagneticmaterialstoinductorsarecomplicatedandrequiretailoringinductorandarchitecturetogether;Forexample:• Qualityfactor𝑄 = CDEF indicatesinductor’sperformance

𝑄GH = 𝜔 D𝐿JH + Δ𝐿

𝑅JH + 𝜔 D𝜇′′𝜇′ D Δ𝐿

D.W.Lee,2008

D.S.Gardner,2009

• Increasinginductancebyaddingmagneticmaterialislimitingbothpeakqualityfactor,andthefrequencybandinwhichitisobtained


EyalAklimi,2017


Existingmetricspaintaconfusingpictureofinductors’usefulnessinthecontextofanactualconverter (e.g.Q-factorlackinginfooncurrentsaturation!)• Examples:Inductance𝐿[𝐻] |Inductancedensity 𝑛𝐻 𝑚𝑚5⁄ |QualityFactor|PeakQualityFactor|CurrentDensity𝐼TUV 𝐴 𝑚𝑚5⁄ |EffectiveInductorEfficiency𝜂E_XYY |𝐿JH 𝑅TH⁄ 𝑛𝐻 Ω⁄

Non-linearbehavioralmodelsarerequiredtoaccountforlargecurrentsdistortion• Lumpedmodel(L)→non-ideallinearmodel(S-parameters)→ non-linearmodel(X-parameters)

D.S.Gardner,2009

N.Sturcken,2015N.Sturcken,2015


EyalAklimi,2017

IntegratedMagneticComponents- Comparison

MagLayers

CuLayers

Inductance Copperlosses

Currentsaturation

IntelFIVRSinge turnaircore

none 1+1via

LOW LOW HIGH(none)

Intelw/magneticMulti-turnracetrack cladded

2+1via

1+1via

HIGH MED LOW

IBMWatson(racetrack)Single-turnracetrackcladded

2+1via

1+1via

MED LOW MED

Ferric(toroid w/magnetic)

1 2+1via

HIGH MED LOW

ColumbiaCore-Clad(Multi-turn cladded)

2+1via

2+1via

HIGH MED MED

E.T.Burtonetal.,2015

D.S.Gardner,2010

N.Wang,2012

N.Sturcken,2013

E.Aklimi,2016

InductorStructures FabricationStructuresChallengesComparison

EyalAklimi,2017


E.T.Burtonetal.,2015

Lowcopperlosses(onlyoneturn)Nocurrentsaturation(aircore)LowfabricationcomplexityLowinductance

EyalAklimi,2017


D.S.Gardner,2010

HighinductancedensityMediumcopperlossesMediumfabricationcomplexityLowsaturationcurrent

EyalAklimi,2017

LowcopperlossesMediumtolowinductanceMediumsaturationcurrentMediumfabricationcomplexity


N.Sturcken,2013

N.Wang,2012

Note:versionsofthistopology(stripline,slab)havebeenproposedbymanyothers(Intel,Tyndall,etc.)

EyalAklimi,2017


N.Sturcken,2013N.Sturcken,2015 K.L.Shepard,2012

HighinductancedensityMediumfabricationcomplexityMediumcopperlossesLowsaturationcurrent

EyalAklimi,2017

400%


Core-Clad(top)

Traditionalsolenoid(bottom)

Singleinductor

E.Aklimi,2016

E.Aklimi,2016

HighinductancedensityMediumcopperlossesMediumsaturationcurrentHighfabricationcomplexity

EyalAklimi,2017

AdvancedTopics

Influenceofprojecteddigitalmicroelectronicstrends• Availabilityofchipreal-estateforInductors↓astransistorsdensity↑• IVRcurrentrequirements↑aspowerdensity↑• IntegratedinductorsshareICrealestatewithI/O,soareaforinductors↓ asI/Odensity↑.Nonetheless,IVRusuallymeans↑powerwith↓I/O

EyalAklimi,2017

AdvancedTopics

• Betterhighfrequencybehaviorisdemonstratedwhenmagneticfluxisalignedwithhardaxis(HA)ofthecore(becausedomainmagnetizationrotationdominatesoverdomainwallmotion)• Elongatedrectangularshapesusuallyinduceeasyaxis(EA)shapeanisotropytothelongedgeofas-depositedfilms

HA

EA

200𝜇𝑚

E.Aklimi,2016

• Anisotropymustbeinduced:• In-situ:thisisanewdepositiontoolsrequirementforbothPVD-sputtering,andelectroplating• Post-depositionbyannealinginstrongmagneticfield:limitedbythermalbudgetofICsfront-end

• CladdedstructuresarebetterataligningfluxwithHAthroughoutthecore

EyalAklimi,2017

AdvancedTopics

• Magneticsfilmsareparticularlychallengingtopattern(evenincomparisontothickAl/Cumetallization):• Additive:photoresistlift-offofthicksputteredlayers• Additive:through-maskelectroplating• Subtractive:hard-maskdeposition,andetchofferrousalloys• Subtractive:damascenerequiresCMP

• Worsewithlaminations

N.Sturcken,2013

EyalAklimi,2017

CreativeWaystoMakeInductors

Microtube inductorsProcessesin2Dbutfunctionsin3D

X.Yu,2015S.-Y.Wu,2015

MoldedinductorsSerialmethod,notsuitableformass-production

EyalAklimi,2017

• ReducingSoC PowerConsumptionusingIntegratedVoltageRegulators,DanielNenni,2011http://www.semiwiki.com/forum/content/694-reducing-soc-power-consumption-using-integrated-voltage-regulators.html

• BMR450TechnicalSpecification,Ericsson,2011• EN5364QIDatasheet,Altera(formerlyEnpirion),2013• FIVR—Fullyintegratedvoltageregulatorson4thgenerationIntel®Core™SoCs,EdwardABurton,GerhardSchrom,FabricePaillet,JonathanDouglas,WilliamJ

Lambert,Kaladhar Radhakrishnan,MichaelJHill,APEC2014• Electronicsatitsbest,workingvoltageratingsforinductors,Coilcraft 2014https://kenvins.wordpress.com/2014/10/09/working-voltage-ratings-for-inductors/• DanHarburg,DartmouthThayerSchoolofEngineering,Microfabricated Inductors,2012http://engineering.dartmouth.edu/microeng/inductors%20full.jpg• RecoveryAct:IntegratedDC-DCConversionforEnergy-EfficientMulticoreMicroprocessors,FinalTechnicalReport,2012

https://www.osti.gov/scitech/servlets/purl/1073611• IntegratedMagneticsforPwrSiP andPwrSoc,PaulMcCloskey,Tyndall,PSMA2014http://www.psma.com/sites/default/files/uploads/tech-forums-

packaging/presentations/is26-integrated-magnetics-pwrsip-and-pwrsoc.pdf• PSCHighFrequencyRFSpiralInductorforWireBondedAssemblies,Datasheet,Vishay2017http://www.vishay.com/docs/61050/psc.pdf• AssemblyMasters(AMI),http://www.assemblymasters.com/air-core-inductors-air-coils.cfm• D.W.Lee,etal.EmbeddedIntegratedInductorsWithASingleLayerMagneticCore:ARealisticOption,PWRSOC2008• Designandrealisation ofintegratedinductorwithlowDC-resistancevalueforintegratedpowerapplications,• F.Zhang,etal,Voltage-ControlledOscillatorintheCoil,2008http://www.cisl.columbia.edu/grads/frank/TEST_CHIP/Chip2/Chip2.html• B.Estibals,Designandrealisation ofintegratedinductorwithlowDC-resistancevalueforintegratedpowerapplications,HAIT2005• E.A.Burton,etal.,FIVR- FullyIntegratedVoltageRegulatorson4thGenerationIntel(R)Core(TM)SoCs,APEC,2014• N.Wang,etat.,Integratedon-chipinductorswithelectroplatedmagneticyokes,JAP,2012• J.Kim,etal.,Anisotropicnanolaminated CoNiFe coresintegratedintomicroinductors forhigh-frequencydc–dcpowerconversion,J.ofphysicsD,2015• E.Aklimi,etal.,Core-CladCMOS- IntegratedInductorswithVerticalMagneticLoopClosure,MMM-Intermag,2016• J.–B.Yoon,CMOS-compatiblesurface-micromachined suspended-spiralinductorsformulti-GHzsiliconRFIcs,IEEEEDL,2002• Chipworks,2011,https://semimd.com/chipworks/page/6/

References

EyalAklimi,2017

• COMSOL,2013,https://www.comsol.com/blogs/comsol-4-4-magnetic-saturation-curves/• R.Clarke,2008,http://info.ee.surrey.ac.uk/Workshop/advice/coils/power_loss.html• Powerlossesinwoundcomponents,http://info.ee.surrey.ac.uk/Workshop/advice/coils/power_loss.html• D.S.Gardner,etal.,ReviewofOn-ChipInductorStructuresWithMagneticFilms,IEEETransactionsonMagnetics,2009• N.Sturcken,IntegratedVoltageRegulatorswithThin-FilmMagneticPowerInductors,thesis,2013.• N.Sturcken,etal.,A2.5DIntegratedVoltageRegulatorUsingCoupled-Magnetic-CoreInductorsonSiliconInterposer,IEEEJSSC,2013• N.Sturcken,etal.,MagneticThin-FilmInductorsforMonolithicIntegrationwithCMOS,IEEEIEDM,2015• E.T.Burton,PackageandPlatformViewofIntel’sFullyIntegratedVoltageRegulators(FIVR),APEC,2015• D.S.Gardner,etal,IntegratedOn-ChipInductorsusingMagneticFilms,PWRSOC2010• N.Wang,etal.,Integratedon-chipinductorswithelectroplatedmagneticyokes,JournalofAppliedPhysics,2012• D.V.Schravendijk,PoweringmulticoreprocessorswithmultiphaseDC/DCs,TI,2015https://e2e.ti.com/blogs_/b/fullycharged/archive/2015/08/18/powering-

multicore-processors-with-multiphase-dc-dcs• TI,Howimportantisphase-to-phasecurrentbalanceinmultiphaseconverters?,2015https://e2e.ti.com/blogs_/b/powerhouse/archive/2015/09/18/how-

important-is-phase-to-phase-current-balance-in-multiphase-converters• K.S.Yeo,HighperformanceRFinductorsandtransformersusingbondingtechnique,US7023315B2,2006• C.R.Sullivan,Integratingmagneticsforon-chippower:Aperspective,IEEETransactionsonPowerElectronics,2013• H.Jia,PackagelevelintegrationofamonolithicbuckconverterpowerICandbondwire magnetics,2010• S.-Y.Wu,3D-printedmicroelectronicsforintegratedcircuitryandpassivewirelesssensors,NatureMicrosystems&Nanoengineering,2015• X.Yu,Ultra-Small,High-Frequency,andSubstrate-ImmuneMicrotube InductorsTransformedfrom2Dto3D,NatureScientificReports,2015• X.Gu,etal.,MitigatingTSV-inducedsubstratenoisecouplingin3-DICusingburiedinterfacecontacts,IEEEEPEPS,2012• S.K.Lee,etal.EvaluationofVoltageStackingfornear-thresholdmulticore,ISLPED,2012• CoolMOS™BenefitsinbothHardandSoftSwitchingSMPStopologies,InfineonTechnologies,2011

References

EyalAklimi,2017

limitations to miniaturization of magnetic components€¦ · • magnetic component (inductor) –...

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