利用电阻场板提高SOILIGBT的性能英文.docx

利用电阻场板提高SOILIGBT的性能英文.docx

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利用电阻场板提高SOILIGBT的性能英文

　第23卷第10期半　导　体　学　报

Vol.23,No.10　2002年10月

CHINESEJOURNALOFSEMICONDUCTORS

Oct.,2002

3ProjcetsupportedbyNationalNaturalScienceFoundationofChina（No.69776041

　YangHongqiang　male,wasbornin1974,PhDcandidate.HisresearchliesinthefieldofSOI,powerdevice,andpowerICs.　HanLei　male,wasbornin1968,PhDcandidate.HeisinterestedinpowerdeviceandsmartpowerIC.

　ChenXingbi　male,wasbornin1931,academicianofTheChineseAcademyofSciences.Hiscurrentresearchincludespowerdevices,smartpowerICsandde2

vicephysics.

　Received8February2002,revisedmanuscriptreceived26April2002○

c2002TheChineseInstituteofElectronicsImprovementofElectricalPerformanceofSOI2LIGBT

byResistiveFieldPlate3

YangHongqiang,HanLeiandChenXingbi

（InstituteofMicro2ElectronicsandSolid2Electronics,UniversityofElectronicScienceandTechnology,Chengdu　610054,China

Abstract:

Theelectricalperformanceincludingbreakdownvoltageandturn2offspeedofSOI2LIGBTisimprovedbyincorporatingaresistivefieldplate（RFPandap2MOSFET.Thep2MOSFETiscontrolledbyasignaldetectedfromapointoftheRFP.Duringtheturning2offoftheIGBT,thep2MOSFETisturnedon,whichprovidesachannelfortheexcessivecarrierstoflowoutofthedriftre2gionandpreventsthecarriersfrombeinginjectedintothedriftregion.Atthesametime,theelectricfieldaffectedbytheRFPmakestheexcessivecarriersflowthroughawiderregion,whichalmosteliminatesthesecondphaseoftheturning2offoftheSOI2LIGBTcausedbythesubstratebias.Fasterturn2offspeedisachievedbyabovetwofactors.DuringtheonstateoftheIGBT,thep2MOSFETisoff,whichleadstoanon2stateperformancelikenormalone.Atleast,theincreaseofthebreakdownvoltagefor25%andthedecreaseoftheturn2offtimefor65%canbeachievedbythisstructureascanbeverifiedbythenumericalsimulationre2sults.

Keywords:

resistivefieldplate;dynamiccontrolledanode2short;turn2offtime;breakdownvoltage;forwardvoltagedropEEACC:

1210;2560

CLCnumber:

TN386　　　Documentcode:

A　　　ArticleID:

025324177（20021021014205

1　Introduction

Powerdeviceiswidelyusedindifferentfields.Butthecontradictiverelationshipamongtheon2statepowerdissipation,breakdownvoltage,andswitchingspeedre2strictsitsuseinmostsituations.Forexample,itisalwaysaproblemthatthelongtimetakentoturnoffanIGBTcannotbereducedwithoutaffectingtheothercharacteristicssignificantly.Somesolutions,forexample,anode2short,mi2nority2carrier2lifetime2control,etc,havebeenputforward

toresolvetheproblemofIGBT.Thetechniqueofanode2

shortisthemosteffectiveone.Itcanreducetheturn2offtimebypreventingtheinjectionofthecarriersandprovid2ingawayfortheexcessivecarrierstodisappearmorequickly.Butthereisstilladrawbackthattheanode2shortstructurewilldecreasetheefficiencyofcarrierinjectionduringon2state,whichcausestheforwardvoltagedropmuchlower.FindinganewstructurethatcanimprovethewholeperformanceofIGBTwillbegreatvaluable.

Differentsolutionsforaboveproblemaredescribedbasedonthedynamiccontrolledanode2short.Neverthe2

less,amongthesemethods,someareunfitforsustaininghighvoltage[1],someneedcomplicateddrivingcir2cuits[2,3],andsomecanonlybeusedinaspecialcir2cuits[4].SomenewstructuresyieldingbetterperformancewiththesamedrivingcircuitsofaconventionalIGBTareexpected.Thatisthepurposeofthispaper.

2　Theoreticalanalysis

ThemostimportantpartsofthenewstructureofIG2BTproposedaretheRFPandthep2MOSFET,whosesourceanddrainareconnectedtotheanodeandbufferre2gionoftheIGBT,respectively.Thep2MOSFETactsasadynamicanode2shortstructureandiscontrolledbythesignaldetectedfromapointoftheRFP,inotherwords,controlledbytheanodevoltageindirectlysincetheRFPisconnectedtothecathodeandanode.AschematicdiagramofthenewstructureofSOI2LIGBTisshowninFig.1,inwhichK,GandAaretheelectrodesofcathode,gateandanodeofaconventionalLIGBT.G1isthegateusedfordynamiccontrolledanode2short.RListheloadresistor

of

Fig.1　SchematicdiagramofthenewstructureIGBT（shadowregionstandsforoxideorRFP

IGBT.ComparedtoanormalIGBT,anadditionalp2MOS2FETisinthisstructure.WhentheIGBTisintheonstate,thedifferenceoftheelectricalpotentialbetweentheanodeandthecathodetakestheminimumvalue,whichcausesminimumgatevoltageofG1.Thenthep2MOSFETwillbeoff,andtheanode2shortstructurewillstopworking.The

on2statepowerdissipationoftheIGBTmaintainsaverysmallvalue.Duringthecourseofturning2off,thepotentialdifferencebetweentheanodeandthecathodeincreaseswiththeincreaseofanodevoltage.Whentheanodevolt2agereachesacriticalvalue,thep2MOSFETwillbeturnedon,whichpreventstheinjectionofthecarriersandmakestheexcessivecarriersofthebaseregiondisappearmorequickly.Thenafasterturn2offspeedisachieved.

Itisnecessarytopointoutthattherearethreephas2esintheturning2offofanormalSOI2LIGBT,andthesec2ondphasecausedbythesubstratebiasisanadditionalpartcomparedtoanormalIGBT[5].Inournewstructure,theelectricfieldaffectedbytheRFPmakestheexcessivecarriersflowthroughawiderregion,whichalmostelimi2natesthesecondphase.Fasterturn2offspeedisachieved.

ItisimportanttodecidethepointfromwhichthegatevoltageofG1isdetected,inotherwords,theratioofthelengthoftheRFPattherightofthispointtothatofthetotal,sinceeithertheon2oroff2stateofthep2MOS2FETisdecidedbyit.Atoolargevalueoftheratioleadstoahighervoltagethanthethresholdvoltageofthep2MOSFETallthetime,whichmakesthep2MOSFETbeal2waysinitson2state.Thentheanode2shortstructurealwaysworks,andtheIGBThasahigherforwardvoltagedrop.Ontheotherhand,toosmallavalueoftheratiocannotturnonthep2MOSFETduringtheturning2offoftheIGBT,whichleadstoaturn2offtimejustlikethenormalone.So,thecompromisebetweentheforwardpowerdissipationandtheturn2offtimeshouldbeconsidered.

3　Simulationanalysis

TMA/MEDICI[7]isusedforsimulationtoverifythevalidationofthetheoreticalanalysisintheparttwo.ThenewstructureforsimulationisshowninFig.1,whichin2dicatesthedimensionalparameters.TheotherparametersaregiveninTable1.DifferentvaluesofL1aregiventoachievetheoptimumresultbyconsideringthetradeoffoftheturn2onperformanceandtheturn2offspeed.Thenor2malIGBTisjustthesameasthenewstructurewithoutthe

5

101　10期YangHongqingetal.:

　ImprovementofElectricalPerformanceofSOI2LIGBT…

RFPandthep2MOSFET,andtheparametersaretheopti2mumonesforthenormalIGBT.Bothofthenewandthenormalstructurearesimulated.

Table1　Parametersforsimulation

Parameters

ValuesUnitConcentrationofnsubstrate15

-3Concentrationofn2drift15-3Concentrationofn2buffer17-3++

20-3Concentrationofchannelregion17-3Thresholdvoltageofp

2MOSFET

6V

Thicknessofthegateoxide

011μmDistancefromthedetectedpointtotherightoftheRFP（L

115,2,215

μmTotallengthoftheRFP30μmRL

2

MΩ/μm

V250VGatevoltageVG15V

Highinjectionlifetime

20

μs

Thecurvesoftheturn2onandturn2offcorrespondingtodifferentvaluesofL1bysimulationareshowninFigs.2and3.Fromthefigures,theconclusioncanbedrawnthatlargerL1leadstopoorerturn2onperformancebut

fasterturning2off.ThecaseofL1=2μmistakenasanex2ampletogivetheexplanationoftheturn2onandturn2offmechanism.

Fig.2　Turn2oncurves　Solidline:

newstructure;Dashline:

normalIGBT

ThepotentialdifferencebetweenthegateG1andthean2odeA,thesourceofthep2MOSFET,versustimeduringtheturning2onandturning2offisshowninFig.4（aand

Fig.3　Turn2offcurves　Solidline:

newstructure;Dashline:

normalIGBT

Fig.4　（aPotentialdifferencebetweenthegateG1andthean2odeduringthecourseofturning2on;（bPotentialdifferencebe2tweenthegateG1andtheanodeduringthecourseofturning2off

（b.AccordingtoFig.4（a,thepotentialdifferenceislargerthanthethresholdvoltageofthep2MOSFETbeforethetimeof715ns,whichturnsonthep2MOSFET,sotheIGBTworksinanode2shortmode,andtheanodecurrentissmallerthanthatofanormalIGBT.Afterthat,thevoltageaddedonG1decreases,thep2MOSFETisnotinitson2stateanymore,whichmakestheanodecurrentrisetothelevelasnormal.Thedegradationoftheturn2onperfor2mancecanbeneglectedsincethedifferencebetweenthe

6101半　导　体　学　报23卷　

turningonofthenewstructureandthatofthenormalIG2BTisverysmall（inFig.1,thecurvesofthenormalcase

andthatofL1=115μmalmostoverlap.

Aftertheturningon,theIGBTreachesitson2state.Accordingtotheresultsofsimulation,thevaluesoftheforwardvoltagedropforthenewstructureandthenormalIGBTarethesame,whichare1143V,whilethevaluesoftheanodecurrentbothequalto112429A/μm.Thisisthepreconditionforcomparingtheturn2offcourseofthetwostructuresofIGBT.

Figure4（bshowsthepotentialdifferencebetweenthegateG1andtheanodeduringthecourseofturning2

off.Duringtheperiodof0to112

μs,thevoltageaddedonG1issmallerthanthethresholdvoltage