英文翻译及文献电子电子功率半导体.docx
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英文翻译及文献电子电子功率半导体.docx
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英文翻译及文献电子电子功率半导体
英文翻译及文献电子电子功率半导体
I.Introduction
Solidstatesemiconductorswitchesareveryinvitingtouseatpulsedpowersystemsbecausetheseswitcheshavehighreliability,longlifetime,lowcostsduringusing,andenvironmentalsafetyduetomercuryandleadareabsent.Semiconductorswitchesareabletoworkinanyposition,so,itispossibletodesignsystemsasforstationarylaboratoryusing,andformobileusing.Thereforetheseswitchesarefrequentlyregardedasreplacementofgas-dischargedevices–ignitrons,thyratrons,sparkgapsandvacuumswitchesthatgenerallyusenowinhigh-powerelectrophysicalsystemsincludingpowerlasers.
Traditionalthyristors(SCR)aresemiconductorswitchesmostlyusingforpulsedevices.SCRhassmallvalueofforwardvoltagedropatswitch-onstate,ithashighoverloadcapacityforcurrent,andatlastithasrelativelylowcostvalueduetothesimplebipolartechnology.DisadvantageofSCRisobservedatswitchingofcurrentpulseswithveryhighpeakvalueandshortduration.Reasonofthisdisadvantageissufficientlyslowprocessofswitch-onstateexpansionfromtriggeringelectrodetoexternalborderofp-njunctionaftertriggeringpulseapplying.ThisSCRfeatureisdefinedSCRusingintomillisecondrangeofcurrentswitching.ImprovementofSCRpulsecharacteristicscanbereachedbyusingofthedistributedgatedesign.Thisisallowedtodecreasethetimeoftotalswitch-onandgreatlyimproveSCRswitchingcapacity.Thus,ABBcompanyisexpandedthesemiconductorswitchusinguptomicrosecondrangebydesignofspecialpulseasymmetricthyristors(ASCR).ThesedeviceshavedistributinggatestructurelikeaGTO.Thisthyristordesignandforcedtriggeringmodeareobtainedthehighswitchingcapacityofthyristor(
=150kA,
=50μs,di/dt=18kA/μs,singlepulse).However,inthisdesigngatestructureiscoveredlargeactiveareaofthyristor(morethan50%)thatdecreasetheefficiencyofSiusingandincreasecostofdevice.
Si-thyristorsandIGBThavedemonstratedhighswitchingcharacteristicsatrepetitivemode.However,suchdevicesdonotintendforswitchingofhighpulsecurrents(tensofkiloamperesandmore)becauseofwell-knownphysicallimitsareexistedsuchaslowdopingofemitters,shortlifetimeofminoritycarriers,smallsizesofchipsetc.
Ourinvestigationhaveobtainedthatswitchesbasedonreverse–switcheddinistorsaremoreperspectivesolid-stateswitchestoswitchsuperhighpowersatmicrosecondandsubmillisecondranges.Reverse–switcheddinistors(RSD)istwo-electrodeanalogueofreverseconductingthyristorwithmonolithicalintegratedfreewheelingdiodeinSi.ThisdiodeisconnectedinparallelandinthebackdirectiontothethyristorpartofRSD.TriggeringofRSDisprovidedbyshortpulseoftriggercurrentatbriefapplyingofreversalvoltagetoRSD.DesignofRSDismadethusthattriggeringcurrentpassesthroughdiodeareasofRSDquasiaxiallyanduniformlyalongtheSistructurearea.Thiscurrentproducestheoncominginjectionofchargecarriersfrombothemitterjunctionstobaseregionsandinitiatestheregenerativeprocessofswitch-onforRSDthyristorareas.SuchmethodoftriggeringforthisspecialdesignofSiplateisprovidedtotalanduniformswitchingofRSDalongallactiveareaintheveryshorttimelikeasdiodeswitch-on.ThefreewheelingdiodeintegratedintotheRSDstructurecouldbeusedasdampingdiodeatfaultmodeinthedischargecircuit.Thisfaultmodesuchasbreakdownofcablelinescanleadtooscillatingcurrentthroughswitch..
IthasbeenexperimentallyobtainedinthatsemiconductorswitchesbasedonRSDcanworksuccessfullyinthepulsedpowersystemstodriveflashlampspumpinghigh-powerneodymiumlasers.ItwasshowninthatRSD-switchesbasedonRSDwaferdiameterof63mm(switchtypeKRD-25-100)andRSD-switchesbasedonRSDwaferdiameterof76mm(switchtypeKRD-25-180)canswitchthecurrentpulseswithsubmilliseconddurationandpeakvalueof120kAand180kArespectively.Threeswitches(switchtypeKRD–25-180)connectedinparallelweresuccessfullytestedunderthefollowingmode:
operatingvoltage
=25kV,operatingcurrentIp=470kA,andtransferredchargeQ=145Coulombs.
During2000–2001,thecapacitorbankforneodymiumlaseroffacilityLUCHwasbuiltatRFNC-VNIIEF.Thisbankincluding18switchestypeKRD-25-100operatessuccessfullyduring5yearswithoutanyfailuresofswitches.
Thisreportissubmittedresultsofdevelopmentofnewgenerationofsolidstateswitcheshavinglowlossesofpowerandhigh-currentswitchingcapacity.
II.DevelopmentofRSD’snextgeneration
ThetechnologyoffabricationofnewRSDstructurehasbeendevelopedtoincreasetheswitchingcapacity.ThisnewstructureisSPT(SoftPunchThrough)-structure-with“soft”closingofspace-chargeregionintobuffern'-layer.
Decreasingofn-basethicknessandalsoimprovingofRSDswitch-onuniformitybygoodspreadingofchargecarriersonthen'-layeratvoltageinversionareprovideddecreasingofallcomponentsoflossesenergysuchaslossesattriggering,lossesattransientprocessofswitch-on,andlossesatstate-on.OurpreliminaryestimationwasshownthatsuchstructuremustprovidetheincreasingofoperatingpeakcurrentthroughRSDapproximatelyin1.5times.
InvestigationswerecarriedoutforRSDwithblockingvoltageof2.4kVandSiwaferdiametersof63,76,and100mmbyspecialteststation.ThemaingoaloftheseinvestigationsisdefinitionofmaximumpermissiblelevelofpeakcurrentpassingthroughsingleRSDwithgivenarea.CurrentpassingthroughRSDandvoltagedroponRSDstructureduringcurrentpassingaremeasuredattesting.InFig.1waveformsofpeakcurrentsandvoltagedropsisshownforRSDwithsizeof76mmandblockingvoltageof2.4kV.
Fig.1.Waveformsofpulsecurrent(a)andvoltagedrop(b)forRSDwithwafersizeof76mmandblockingvoltageof2.4kV
InaccordingwithstudyprogramcurrentwasslowlyincreaseduntilmaximumpermissiblelevelIpm.WhenthislevelwasreachedthesharpriseofvoltageandthanthesamesharpdecayofvoltageforcurveU(t)wasobserved.Reasonofvoltageriseisstrongdecreasingofcarriermobilityathightemperature,andreasonofvoltagedecayisquickmodulationofchannelconductivitybythermalgeneratedplasmathatisappearedinaccordancewithsharpexponentialdependenceforownconcentrationofinitialsiliconintobaseareasofRSDattemperatureof400–
C.
TestswereshownthatthissharpriseofvoltageatmaximumpermissiblecurrentdoesnotleadtoimmediatefaultofRSD.RSDkeepsitsblockingcharacteristic.However,afterpassingofsuchcurrent
wecanobservetheappearanceoferosionfromcathodeforaluminummetallizationofRSDcontacts,andthisfactisevidenceofborderlinestateofdevice.Thesubsequentincreasingofcurrent(morethan
)leadstofusingofSistructure.Therefore,levelIpmisthereferencepositiontodefinethevalueofoperationpeakcurrentforRSD-switchunderlongandrepeatedmanytimesoperatingmode.
Wehavedeterminedthatoperatingpeakcurrent
mustbelessthan80%fromlevel
.Thisratiowasconfirmedbycalculationsandresultsoftestsunder
mode(severalthousandsofshots).
DataoftestresultsfornewgenerationofRSDwiththevariousdiameterofSiwaferareshowninTable1.InthisTableforcomparingresultsofthesametestsforthefirstgenerationofRSDwithsizeof63and76mmareshown.
III.SwitchesbasedonRSDofnewgeneration
Newreverse–switcheddinistorsismanufacturedintwovariants.RSDofthefirstvariantisinthelow-profilemetal-ceramichousing.ThesecondvariantisRSDfabricatedwithouthousingandwithadditionalprotectionofperipheryareafromexternalaction.
Dinistorsplacedintohousingcanbeusedforworkunderasmono-pulsemodeandrepeated-pulsemode.Ifrepeated-pulsedmodeusingtheforcedcoolingofsemiconductordevicesandusingofheatsinkstobothsideofpelletmustbemade.Dinistorswithouthousingconnectsinseries,andsuchassemblycouldbeplacedintoasinglecompacthousing.However,suchassemblycanworkundermono-pulsemodeonly.
OperatingvoltageforswitchtypicallyexceedsblockingvoltageofsingleRSD(
≤2400V),thusswitchisincludedseveralRSDsconnectedinseries.Fig.2.Reverse–switcheddinistorsforpeakcurrentfrom200kAto500kAandblockingvoltageof2400V,encapsullatedinhermeticmetal–ceramichousingandwithouthousing(RSDsizesof64,76,and100mm).
NumberofRSDsincludedinassemblydependsonoperatingvoltageofswitch.Therefore,technicalproblemofswitchdevelopmentismainlyoptimizationofdesignforassemblyofseveraldinistorsconnectedinseries.AlotofspecialinvestigationshavecarriedoutsuchaschoiceofoptimummaterialstoprovidebestcontactsbetweenRSDs,calculationofdynamicforcestoclampassembly,etc.TheseinvestigationsareprovidedsmallandstabletransitionelectricalandthermalresistancesbetweenRSDsthatguaranteeslongandreliableperformanceofswitch.EspecialcomputertechniquehasdevelopedtoselectRSDsforconnectioninseries.AtthisRSDselectionvalueofleakagecurrentandstabilityofblockingvolt-ampsdiagramaremeasuredespecially.ThisselectiontechniqueisallowedexcludethevoltagedividersusingforequalizationofstaticvoltageforeachRSDatassembly.Thus,aftersuchselectionswitchdesigncansimplify,sizesofswitchareincreasedapproximatelyin1.5times,andcostofswitchisincreasedtoo.
Thissolidstateswitchhasoperatingvoltageofupto25kVdc,operatingpeakcurrentofupto300kAatcurrentpulsedurationofupto500μs.RFNC-VNIIEFplanstousesuchswitcha
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