GaN Power HEMT Tutorial: GaN Basics

1 GANPOWERINTERNATIONAL INC Fred Yue Fu ( ),GaNPower International Yue Fu Co-founderand COOGaNPower International Power HEMT Tutorial: GaN Basics12 Fred Yue Fu ( ), GaNPower International Session 1: GaN devices Basics GaN, An Introduction GaN Design, Fabrication and Testing GaN Compact Modeling and Reliability Session 2: Gate Driving Session 3: GaN Applications3 Fred Yue Fu ( ), GaNPower International 1960s1970s1980s20002010 Power Diode GermaniumThyristorSiliconPower BipolarSiliconPower MOSFET SiliconIGBTS iliconSchottky diodeSilicon CarbidePower HEMTGaNPower Devices: History of Evolvements4 Fred Yue Fu ( ), GaNPower International s time to move +substraten-drift regionp+ body contactpolysilicon gatesource contactn+ sourcep-well5 Fred Yue Fu ( ), GaNPower International Properties ComparisonMaterialPropertySiliconSiC-4 HGaNBand-gap(eV) (1E+6V/cm) (cm2/V-Sec.)

2 14509002000 ElectronSaturationVelocity(1E+6cm/Sec.)1 02225 ThermalConductivity(W/cm2K) (FOM)= " E%&167530006 Fred Yue Fu ( ), GaNPower International Power Devices: ApplicationsGaN HEMT Silicon Super Junction MOSFET EncroachingSiC MOSFETS ilicon IGBTE ncroachingSource: YoleDevelopment: How Power electronics will reshape to meet 21st century challenges? ISPSD 20157 Fred Yue Fu ( ), GaNPower International (cm-2)1E+95E+83E+81E+3to1E+5 Latticemismatch(%) (W/cm-kat25oC) (%)5425340 Off-stateleakagehighhighlowlowReliabilit yandyieldlowlowlowhighLateralorVerticald evicelaterallaterallaterallateralorverti calIntegrationpossibilityVeryhighModerat eModerate-Substratesize(mm)30015010050 Substratecost(relative)LowhighLowVeryhig hSubstrate Materials for GaN HEMTP owerRF8 Fred Yue Fu ( ), GaNPower International HEMTS ilicon LDMOSS implified E-GaN vs.

3 LDMOS Device StructuresSilicon SubstrateSDILDO xideN-Silicon EpiPoly SiGP-BodyN+P+N+Body DiodeSilicon SubstrateAlN Nucleation LayerGaN LayerAlxGa1-xNSD2 DEG ChannelGILDP-GaNAlGaN / GaN Buffer Layer9 Fred Yue Fu ( ), GaNPower International E-Mode vs. D-Mode GaN HEMTE-Mode GaN HEMTD-Mode GaN HEMTAlxGa1-xNSDILDP-GaNAlxGa1-xNSDGILDP- GaNSilicon SubstrateAlN Nucleation LayerGaN Layer2 DEG ChannelAlGaN / GaN Buffer LayerSilicon SubstrateAlN Nucleation LayerGaN Layer2 DEG ChannelAlGaN / GaN Buffer LayerG10 Fred Yue Fu ( ), GaNPower International Junction MOSSiCCascode GaNPartIDGPI65015 TOxxxxxxxxxxxxxxxxxxxxxxxxxxxRated Voltage650V700V650V600 VRon92m 125m 100m 150m *Qg30443755100900 Good: GaN is normally onby nature: easy to fabricate Si like gate control with higher Vth Reverse conduction with LV MOS body-diodeBad.

4 Comparatively lower performance Controlling silicon rather than GaN gate May need extra TVS device to protect MOS Difficult to match Cossof GaN and MOS Still has QrrCascode GaN HEMT11 Fred Yue Fu ( ), GaNPower International GaN HEMT Cascodecanmakepackagemorecomplicatedwith 3componentsandceramicsubstrate CanbemoreexpensivethanpureE-mode Also,cascodeisnotfeasibleforlowvoltage(< 200V)GaN,duetotheRdsonportionfromMOSisto ohigh: for600 Vdevice,RdsonfromMOScontributelessthan5% ; for100 Vdevice,MOScancontributemorethan30%ofthe Rdson,whichisimpractical1. System Plus Consulating: Alex Lidow Johan Strydom Michael de RooijDavid Reusch, GaN TRANSISTORS FOR EFFICIENT Power CONVERSION, Wiley12 Fred Yue Fu ( ), GaNPower International E-Mode GaN HEMT with p-GaN GIT: Gate withOhmic Contact and Current ControlGate withSchottky Contact and Current Control1 Kevin J.

5 Chen, Understanding the Dynamic Behavior in GaN-on-Si Power Devices and IC s, Integrated Power Conversion and Power Management, 20182 Greco, G., Iucolano, F., & Roccaforte, F. Review of technology for normally-off HEMTs with p-GaN gate. Materials Science in Semiconductor ProcessingGITp-GaNp-GaN13 Fred Yue Fu ( ), GaNPower International no Avalanche Breakdown in GaN? GaNhasaveryhighcriticalelectricfield(10t imesthatofSi,onparwithSiO2orSiNalready) Lateraldevicestructurecauseselectricfiel dcrowding,particularlyinoverlyinginsulat ors GaNHEMT ismorelikeaceramiccapacitorbreakdowninth eoverlyinginsulators,wherepeakelectricfi eldtookplace Ifbreakdowneveroccurs,thedevicesufferspe rmanentdamage Designmargin(>30%)forGaNisusuallymuchhig herthanthatofSi(whichonlyhas10%)Michael A Briere, Understanding The Breakdown Characteristics Of Lateral GaN-Based HEMTs PotentialE-FieldSiNAlGaNGaNGaNAlGaNSiN1D Cut14 Fred Yue Fu ( ), GaNPower International no P-type GaN HEMT Like PMOS?

6 SihasbothNMOSandPMOS,forNMOS,currentisca rriedbyelectronswhileinPMOS,currentiscar riedbytheholes However,forGaNHEMT,thereisnoP-typeGaNHEM Tyet First,ionimplantationandsubsequentanneal ingofmagnesiuminGaNisverydifficulttoachi eve Second,holemobilityinGaNisverylow(30cm2 ) GaNmonolithicICsarerealizedeitherbyusing complementaryE-modeandD-modeGaN,orusingE -modeGaNonly15 Fred Yue Fu ( ), GaNPower International E-mode GaN Vg-maxis Limited to (A)Vg (V) Gate Leakage UnlikeasiliconMOS,theP-GaN/AlGaN/GaNcanb eviewedasaPINdiodestructurewithadepletio nregion Within-situdopedp-typedopant(Magnesium)f orp-GaNlayer,thedepletionregionextendsov erthethicknessoftheGaN2 DEGchannelforVg=0V,thusinterruptsthechan nelbelowthegateregion Whenapositivegatebiasisapplied,the2 DEGchannelisre-established,yieldingtoon- stateconditions FortheP-GaN/AlGaN/GaNgatestack,aTDDB(Tim eDependentDielectricBreakdown)needstobea nalyzedforpropermaxgatevoltagewithlongte rmreliabilityconcerns Ithasbeendeterminedthatmaximumratingof6~ 7 Vforp-GaNHEMT ismostappropriateAlxGa1-xNSDGILDP-GaNSil icon SubstrateAlN Nucleation LayerGaN Layer2 DEG ChannelAlGaN / GaN Buffer Layer16 Fred Yue Fu ( )

7 , GaNPower International Collapse PhenomenonAtlargenegativegatebias,electr onsfromthegateorsubstratemayleaktothetra pstatesclosetothe2 DEGchannel,creatinga virtualgate andmodulatethedepletionregion17 Fred Yue Fu ( ), GaNPower International Collapse: TCAD Transient SimulationTime (Ps)Drain/Gate Voltage (V)Drain VoltageGate VoltageStressDrain Voltage (V)Drain Current (A/m)Before StressAfter StressTime (Ps)Drain Current (A/m)Drain CurrentBefore StressAfter StressVoltage Stress18 Fred Yue Fu ( ), GaNPower International Session 1: GaN devices Basics GaN, An Introduction GaN Design, Fabrication and Testing GaN Compact Modeling and Reliability Session 2: GaN Gate Driving Session 3: GaN Applications19 Fred Yue Fu ( ), GaNPower International Semiconductor MaterialsFinal Power Supply ProductsSubstrateEpi-waferFabricationsGa N Power Device Supply ChainPCB AssemblyUL, CE, CCC CertificationGaNPower 6 inch GaN Wafer (real photo)PackagingTestingPackaged GaN Devices20 Fred Yue Fu ( ), GaNPower International GaN Power Devices Are Fabricated?

8 Device Design and LayoutCircuit Probing(Wafer level testing)Packaging (Wire-bond)Packaging (Bumping)New Lead frame Design1 Epitaxial Wafer1 Device Fabrication23444 Final Testing (Packaging Level)521 Fred Yue Fu ( ), GaNPower International Design Stage (TCAD Simulation) 1P-GaN HEMT Device StructureDevice StructureZoom-in12P-GaN2 DEGVgs@0V12 Conduction BandValence BandFermi LevelConduction BandValence BandFermi LevelP-GaNAlGaNGaNAlGaNGaN - . 1 Simulated Using Crosslight NovaTCADVgs@6 VConduction BandValence BandQuasi-Fermi LevelP-GaNAlGaNGaNSGD1 Vgs@0VG(*Simulated using Ohmic Gate Contact)AlGaNGaN2 DEG2 DEG22 Fred Yue Fu ( ), GaNPower International Design Stage (TCAD Simulation) 1 Silicon SubstrateAlNSeed LayerAlGaN Buffer LayerAlGaN Buffer LayerSGDAlN2 DEG Electron conc.

9 @ Equilibrium (0V on all Terminals)2 DEG Electron conc. @ Vd=200V Vg=Vs=02 DEG Electron conc. @ Vd=400V Vg=Vs=0 Simulated Using Crosslight NovaTCADD epletion Region Propagates 23 Fred Yue Fu ( ), GaNPower International Plot @ Vd=700V Vg=Vs=0 VPotential Plot @ Vd=100V Vg=Vs=0VE-Field Plot @ Vd=700V Vg=Vs=0VE-Field Plot @ Vd=100V Vg=Vs=0 VGaN Design Stage (TCAD Simulation)Simulated Using Crosslight NovaTCAD 1 Insulator Region (SiN)SGDSGDSGDSGD24 Fred Yue Fu ( ), GaNPower International Inc. 1 GaN Design Stage (TCAD Simulation)SxxCompressive Stress Inadditiontostresscausedbymateriallattic emismatch, Stressengineeringmayhelptoachieveenhance mentmode?Simulated Using Crosslight NovaTCADSiNLayer25 Fred Yue Fu ( ), GaNPower International Process Flow for GaN Epi-layerSi/SiC/Al2O3 SubstrateAlN Nucleation LayerP-GaNSi/SiC/Al2O3 SubstrateSi/SiC/Al2O3 SubstrateAlN Nucleation LayerSi/SiC/Al2O3 SubstrateAlN Nucleation LayerGaN / AlGaN Buffer LayerSi/SiC/Al2O3 SubstrateGaN / AlGaN Buffer Layer12345 TheGaNEpiwaferisfabricatedfromeitherSi, (MetalOrganicChemicalVaporDeposition)for lowcostandhighthroughput 1 GaN LayerGaN / AlGaN Buffer LayerGaN LayerAlxGa1-xN Barrier LayerAlxGa1-xN Barrier LayerAlN Nucleation Layer26 Fred Yue Fu ( ), GaNPower International GaN-on-Sapphire HEMT Fabrication ExampleFirstGenerationGaNHEMT.

10 WithbreakdownvoltageBV=480V,Ron,sp=12m *cm21stGenFirst GenerationThirdGenerationGaNHEMT(NovelCr ystalLatticeDesign):BV=850V,Ron,sp=3m *cm2 This work3rdGenThird GenerationSecondGenerationGaNHEMT(Standa rdDesign):withbreakdownvoltageBV=700V,Ro n,sp=4m *cm2 Drain Voltage (volts) Current (mA)020406080100 VGS = - 6 VVGS = - 5 VVGS = - 4 VVGS = - 3 VVGS = - 2 VVGS = - 1 V2nd GenSecond Generation 227 Fred Yue Fu ( ), GaNPower International Steps(D-mode HEMT)1 WaferCleaning2 Mask#1:MesaEtching3 RIEMesaEtching4 Mask#2:S/DContacts5 OhmicContactDeposition6 Mask#3:GateLithography7 SchottkyGateDeposition8 GrowthofPassivationLayer9 Mask#4:ContactHoleOpening10 Mask#5:FieldplateandmetallizationSimplif iedGaN-on-SapphireHEMTP rocessFlow(GaN-on-siliconissimilar):Sili con/Sapphire substrateGaNBufferAlGaNSDG 2 MesaPassivationMesa28 Fred Yue Fu ( ), GaNPower International Inc.