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nHotCarrierReliabilityofn-channelLateralDiffusedMetalOxideSemiconductorFieldEffectTransistor(LDMOS)Student:Kuang-WanLinAdvisor:Jone-FangChenInstituteofMicroelectronicsDepartmentofElectricalEngineeringNationalChengKungUniversityTainan,Taiwan,R.O.CThesisforMasterofScienceJune18th2004In***n0.5μmLDMOSMOSFETIIMOSFETLDMOSstress(KirkEffect)LDMOS(substratecurrent)LDMOSstress(non-LDD)MOSFETLDMOS(relaxation)MOSFET(lifetimemodel)III***IVHotCarrierReliabilityofn-channelLateralDiffusedMetalOxideSemiconductorFieldEffectTransistor(LDMOS)KuangWanLin*,JoneFangChen**ChengKungUniversity,Tainan,TaiwanAbstractThehotcarrierreliabilityofconventionalMOSFETsisestablishedcompletelybyotherauthors.However,fewerauthorsstudythehotcarrierreliabilityofLDMOStransistors.Thethesiswillstudythehotcarrierreliabilityofn-channelLDMOStransistors.IusethemethodbasedontheconventionalMOSFETstoinvestigateLDMOStransistors.IdiscoverthatthreemaindifferencesbetweenconventionalMOSFETsandLDMOStransistors:1.Kirkeffect,2.degradationsaturation,3.relaxationphenomenon.Becauseofthedifference,theIsubvs.τwillnotbethesameastheconventionalMOSFETs.*:Thestudent**:TheadvisorVAcknowledgementsVI–VIIContentsAbstractIEnglishabstractIVAcknowledgementsVContentsVIITableCaptionsIXFigureCaptionsXChapter1Introduction1.1TheBasicsofLDMOStransistor11.2AQuickReviewonHotCarrierReliabilityofLowVoltagedevices21.3AbouttheThesis5Chapter2HotCarrierReliabilityofLowVoltageMOSFET2.1DeviceParametersthatareImpactbyHot-CarrierDamage172.2Stressmethodology172.3Lifetimemodel19Chapter3DegradationbehaviorofLDMOStransistor3.1KirkEffect283.2DegradationSaturation303.3DeviceRelaxation31VIIIChapter4HotCarrierReliabilityofLDMOStransistor4.1LifetimemodelofLDMOStransistor764.2ThecorrectionofstressmethodologyforHighVoltageDevices77Chapter5ConclusionandFutureWork5.1Conclusion885.2FutureWork89IXTableCaptionsTable1-1TheCategoriesofLDMOSinthesis.Table3-1Thedefinitionofallparameters.XFigureCaptionsFig.1-1ThestructureofLDMOS,Asymmetric(a),andSymmetric(b)Fig.1-2Thegenerationofhotcarrier.Fig.1-3Lateralelectricfieldversusdistancebetweenthesourceanddrainofa0.25-μmn-MOStransistorwith2.0Vappliedtothedrain,showingthehighfieldregionatthedrainjunction.Fig.1-4SubstratecurrentcharacterizedasafunctionofVgwithVdasaparameterFig.1-5TherelationshipofdegradationandthemagnitudeofIsub.Fig.1-6Representationoftheoxidewiththedifferenttypesofdamagethatcanexistintheoxide,andattheSi-SiO2interface.Fig.1-7Theinstrumentofexperiment.Fig.1-8Theoutlookofsample.Fig.1-9Theorganizationofthethesis.Fig.2-1TypicalId-VdcharacteristicsofanNMOSFETbeforeandafterhot-carrierstressing.Fig.2-2Idvs.Vgcharacteristicsbeforeandafterhot-carrierstressing.Fig.2-3Thestressmethodology.Fig.2-4DevicelifetimeτversusIsub/ZforvarioustechnologiesFig.2-5Lifetimeversusdutycyclemeasuredafterdynamic(ac)hot-carrierstressing.Fig.3-1ThedegradationofLDMOStransistorsinIdvs.Vd.Fig.3-2ThedegradationofLDMOStransistorsinIdvs.Vg.Fig.3-3ThedegradationofLDMOStransistorsinsubthresholdregion.Fig.3-4AllparametersofLDMOStransistorsdegradewithtime.XIFig.3-5Dopingprofileofann-p-ntransistorwithcollectorepitaxiallayerFig.3-6Kirkeffect:(a)cross-sectionofn-p-nBJT;(b)spacechargedistributioninthebase-collectorreversebiasedjunctionforverylowcurrents;(c)space-chargedistributionofthebase-collectorjunctionforhighercurrentlevels.Fig.3-7Electricfielddistributionsasafunctionofdistanceforvariouscollectorcurrentdensities.ThedopingprofileisshowninFig.3-5.Fig.3-8CalculatedLDMOSequipotentiallinesatVd=250V(BV=500V),atVg=0V(a)andVg=20Von0.1umoxide.Dashedlinesindicateregionsofhighcurrents.Fig.3-9Isubvs.VgcharacteristicsofasymmetricLDMOStransistor.Fig.3-10Isubvs.VgcharacteristicsofsymmetricLDMOStransistor.Fig.3-11Isub-VgandDegradation-VgofsymmetricLDMOStransistor,theΔGmmax/Gmmaxisgotin100minutes.Fig.3-12Isub-VgandDegradation-VgofasymmetricLDMOStransistor,theΔGmmax/Gmmaxisgotin100minutes.Fig.3-13Isub/Idvs.1/Vdof.25technologylow-voltageMOSFETFig.3-14Isubvs.1/VdofLDMOSFig.3-15StresstimevariationofGmdegradationandVtshiftatId=10nAforadevicewithLeff=0.8μmandtox=20nm.Stress:Vd=6.6V;Vg=3.2V.Fig.3-16twostagedegradationFig.3-17DegradationsaturationinasymmetricLDMOStransistors.Fig.3-18DegradationsaturationinsymmetricLDMOStransistors.XIIFig.3-19Impactoflifetimebydegradationsaturation.Fig.3-20DegradationrecoveryphenomenonFig.3-21Stress3000minutes(a)andobservethedegradationafterstressing(b).Fig.3-22MeasureGmmax13timesofthefreshsymmetricLDMOStransistor.Fig.3-23Measurementwithinterruptionandwithoutinterruptionafterstoppingstressing.Fig.3-24Thedegradationphenomenonindifferentdevices.Fig.3-25LogId-Vgcharacteristicsfora2-mmtransistortakenatvarioustimesduringstressing.Thearrowsindicatethedirectionofthedegradationduringstressing.Fig.3-26MeasureVt5times.Fig.3-27RelaxationinsymmetricLDMOStransistors.Fig.3-28RelaxationinasymmetricLDMOStransistorFig.3-29Measure3timesGmmaxofsymmetricLDMOStransistorwhileinterruptstressing.Fig.3-30Measure3timesGmmaxofasymmetricLDMOStransistorwhileinterruptstressing.Fig.3-31Themagnitudeofdegradationamongallparame