考虑温度效应的统计学EM分析方法在FINFET设计上的应用

Thermal-awareSEBMethodologyforFinfetdesignEM

signoffStatisticalEMBudgeting(SEB)

Introduction2©2017ANSYS,

Inc.July31,

2017ANSYSUGM

2017HistoricallydesignershavecomparedinterconnectDCaveragecurrenttoaconservativefixedlimitas,S=Jdesign/

JmaxSoifS<=1,the“design”isreliable,whileanyinterconnectwithS>1needstoberedesigned.Fromtheprocessreliabilityperspective,EMdegradationisinherentlystatistical.Thereisalwaysobservedawidedispersioninthetimesobservedforidenticallysizedandstressedsegmentsofinterconnecttoprogressto

failure.Whenreliabilitydesignisdesignedtomean“achievingachip-levelreliabilitygoal,fixedcurrentdensitydesignlimitsbecomemathematicallyarbitrary.Onlythetotalstatisticalrisktothechipisthemeaningful.TheniftheEMreliabilityimpactofeachsegmentofinterconnectateachstresslevelcanbeaccountedfor,thechip-levelEMreliabilitygoalcanbebudgetedamongclassesofinterconnectorchipdesignsubdivisionstominimizetheperformance

limitations.SEB

MethodologyStatisticalEMBudgeting(SEB)isadesign-specificEMreliabilityevaluationmethodwhichcombinesdesigninputswithEMperformanceforeachinterconnectwiretocomputeatotalfailureratefortheproduct.A“pass”isascertainedifthedesignstaywithinthefailure

budget.SEBgivesthedesignerssomeflexibilityindesignwithoutimposingahardEMlimitforthewholeproduct,thusenablinghigherperformancewithoutcompromising

reliability.3©2017ANSYS,

Inc.July31,

2017ANSYSUGM

2017FailureinTime(FIT)Calculation

perWireLT=lifetimeeg5or10

years.

=stdnormalcumulativedistribution

probabilitySdc=severityratioofIdc,

I/Imax:I->from

design,Imax->definedindesignrule

manual.n=currentdensityexponent(from

foundry)MTF=mediantimeto

failureMTF(Tfit)=MTF(Tamb)*exp(Ea/Kb*(1/(Tfit+273)-1/(Tamb+273)))Tamb=AmbientTemperature;Tfit=Tamb+∆Tfrom

self-heating

=sigma,spreadinlifetimedistribution(from

foundry)FITi

=(-10)9*

ln 1-

ln(SDCn

*(LT/MTF))LT

4©2017ANSYS,

Inc.July31,

2017ANSYSUGM

2017Why

SEB5©2017ANSYS,

Inc.July31,

2017ANSYSUGM

2017q EMchallengeonadvancedFinFet

processq EMissignificantlyimpactonFEOLthermalcouplingand

self-heatingq Verydifficulttosign-offEMduetoEMlimitdegraded

significantly.q Life

Timeq EMspecdefinitioninDRMarebasedon10Ylifetime.Howabout5Ylife

time?q Realapplication:5%xLifetime125c+95%xLifetime

85cq Fromonenettoa

designq IfeverynetsatisfyEMspec,thedesignhavehighreliability?

NO!For

example：Condition:TSMCN10,10Ylife

timeSdc（I/Imax)=0.8,failrate=0.15%(1500PPM).IftherearemanynetswithSdcmorethan0.8,thetotalfailrateismore

high.Usually,SOCfailrate<

0.1%FIT

calculationStatistical EM Budgetingevaluation method whichis a design-specific EM reliabilitycombines design inputs with EMperformanceforeachinterconnectwiretocomputeatotalfailureratefortheproduct.A“pass”isascertainedifthedesignstaywithinthefailure

budget.FITtotal∑i∑j∑

kFIT(i,j,k)Sub-divisions6©2017ANSYS,

Inc.July31,

2017ANSYSUGM

2017classeswiresThermal-AwareSEB

FlowRedHawkTotemTechfile/LIB

/Dev

ModelsLEF/DEF/GDSDSPFw/Signal

RCFoundrySH

InputP/GwireIrms

infoSignalwireIrms

infoSelf-heatcalculationincludingthermalcouplingWireSelf-heat

ReportInstSelf-heat

ReportThermalProfile

/Back-annotationPowerEM

RunSignalEM

RunPre-ThermalThermalFITComputation

EngineFIT

reportFIT

MapFIT

calculation7©2017ANSYS,

Inc.July31,

2017ANSYSUGM

2017Self-heatingimpacton

EMEM@105w/oSH150010005000>100 >110 >120 >130 >140 >150 >160 >170 >180 >1908©2017ANSYS,

Inc.July31,

2017ANSYSUGM

2017EM@105w/

SH150010005000>100 >110 >120 >130 >140 >150 >160 >170 >180 >190@105Cw/o

Self-heating@105w/

Self-heatingNumberofEM

violations25812664MaxEM

violation168%197%Total

FIT23416Self-heatingResult:instancedelta

TThemaxdeltaTis

11.8C9©2017ANSYS,

Inc.July31,

2017ANSYSUGM

2017InstanceDeltaT

MapWireTemperature:Maxtemperature

116.5CWireTemperatureMap:

M110©2017ANSYS,

Inc.July31,

2017ANSYSUGM

2017FIT

correlation11©2017ANSYS,

Inc.July31,

2017ANSYSUGM

2017EMsign-offbythermal-aware

SEBDesignershouldfix2664EMviolationsbytraditionalEM

sign-offmethod.