等离子体刻蚀凹栅槽影响AlGaN-GaNHEMT栅电流的机理

2811200711CHINESEJOURNALOFSEMICONDUCTORSVol.28No.11Nov.,20073(:2002CB311903)(:KGCX22SW2107)­.Email:[e-mail]2007205226,2007207205Z2007AlGaN/GaNHEMT3­(,100029):AlGaN/GaNHEMTs.,AlGaN/GaNHEMTs,.AFMXPSAlGaN,AlGaN,,AlGaN;,AlGaNN,Al2GaNn,,.,AlGaNN.:;;;NEEACC:2570:TN325+13:A:025324177(2007)11217772051AlGaN/GaNHEMTs[1,2].,AlGaN/GaNHEMTs.,AlGaN/GaNHEMTsf=4GHz,12W/mm,(PAE)58%[3].SiCAlGaN/GaNHEMTs32W/mm,PAE50%[4].,,GaNAlGaN2DEG,[5,6].,,.,,AlGaN/GaNHEMTsX,.,,,GaNHEMTs.,,2DEG,2DEG,[7].,,,AlGaN/GaNHEMTs[7,8].,,AlGaN/GaNHEMTs[5,7],..Cai[9]F,,,F,.GaN,ICP2RIE[10,11].,AlGaN/GaNHEMTs[7,12].(AFM)GaN,X(XPS)AlGaN.,,.281AlGaN/GaNHEMTsFig.1SchematicofAlGaN/GaNHEMTswithre2cessed2gatestructure2AlGaN/GaN,(MOCVD),50mm(0001).315mGaN,110nmGaN,25nmAl0.2Ga0.8N.,1161013cm-2,1300cm2/(Vs).0125mAlGaN/GaNHEMTs,1.Ti/Al/Ti/Au4,75050sN2(RTA),l0-6cm2.,108/.ZEP520,0125m.,ICP2RIEAlGaN.Cl2/BCl3Cl2BCl32515sccm,ICPRF7505W.,AlGaN6nm/min,70s,7nm.ZEP520.,UVIII,Ni/Au,0125m,120m.3,AlGaN/GaNHEMTs.-512V-311V,173mS/mm251mS/mm;.2AlGaN/GaNHEMTsFig.2Comparisonsofconventionalplanarandre2cessedAlGaN/GaNHEMTsSchottkygatecharacteris2ticAlGaN/GaNHEMTs.2Al2GaN/GaNHEMTs,2Vgd-400V.Vgd=-40V,GaNHEMT40A/mm,466A/mm,10.,AlGaN/GaNHEMTs.1mA/mm.2,8716V,6614V,.ICP2RIE,.,,,,;ClGaN,Cl.GaN,AFMAlGaN,XPSAlGaNCl.AFMAlGaN,AlGaN.3AlGaNAFM.x,y,z.AFM,AlGaN,AlGaN,.RMSAFM877111:AlGaN/GaNHEMT3AFMAlGaN(a);(b)Fig.3AlGaNsurfaceroughnesspicturesmeasuredbycontactmodeAFM(a)Beforeetching;(b)Afteretching,AlGaN112nm,AlGaN3nm,3nm.I=JdS,.,AlGaN,2.,AlGaN,,.,ICP2RIEAlGaN/GaNHEMTs.,.XPSAlGaN.4AlGaNGa3d,Ga2pN1sX.RF5W,4(a)[13]Ga2pXPS,AlGaN.4(b)(c)N1sGa3d4XPSFig.4XPSofN1s,Ga2p,Ga3dandCl2pspectraforsamplesbeforeandafterdryetching977128,N1s/Ga3d1.20,N1s/G3d1103,ICP2RIEN1s/G3d,AlGaNN,N.XPSCl,4(d)AlGaNClX.,ClXPS.BCl3/Cl2,GaN,AlGaNGaCl3AlCl3Cl.ICP2RIEGaN,N,AlGaNN.GaN,N.,NAlGaN,n.AlGaN,,,,,.4Al2GaN/GaNHEMTs,,.AFMAlGaN,ICP2RIE,,AlGaN,,.XPS,AlGaNN,Al2GaNn,,.AlGaN/GaNHEMTs,,.[1]SaitoW,KuraguchiM,TakadaY,etal.HighbreakdownvoltageundopedAlGaN2GaNpowerHEMTonsapphiresub2strateanditsdemonstrationforDC2DCconverterapplication.IEEETransElectronDevices,2004,51(11):1913[2]LeeC,SaunierP,YangJinwei,etal.AlGaN2GaNHEMTsonSiCwithCWpowerperformanceof4W/mmand23%PAEat35GHz.IEEEElectronDeviceLett,2003,24(10):616[3]ChiniA,ButtariD,CoffieR,etal.12W/mmpowerdensityAlGaN/GaNHEMTsonsapphiresubstrate.ElectronLett,2004,40(1):73[4]WuYF,SaxlerA,MooreM,etal.30W/mmGaNHEMTsbyfieldplateoptimization.IEEEElectronDeviceLett,2004,25(3):117[5]WangWK,LinPC,LinCH,etal.Performanceenhancementbyusingthen+2GaNcaplayerandgaterecesstechnologyontheAlGaN2GaNHEMTfabrication.IEEEElectronDeviceLett,2005,26(1):5[6]CoffieR,ButtariD,HeikmanS,etal.p2cappedGaN2AlGaN2GaNhigh2electronmobilitytransistors(HEMTs).IEEEElectronDeviceLett,2002,23(10):588[7]OkamotoY,AndoY,NakayamaT,etal.High2powerre2cessed2gateAlGaN2GaNHFETwithafield2modulatingplate.IEEETransElectronDevices,2004,51(12):2217[8]MoonJS,WuS,WongD,etal.Gate2recessedAlGaN2GaNHEMTsforhigh2performancemillimeter2waveapplications.IEEEElectronDeviceLett,2005,26(6):348[9]CaiY,ZhouYG,LauKM,etal.ControlofthresholdvoltageofAlGaN/GaNHEMTsbyfluoride2basedplasmatreatment:fromdepletionmodetoenhancementmode.IEEETransElec2tronDevices,2006,53(9):2207[10]LeeYH,KimHS,YeomGY,etal.EtchcharacteristicsofGaNusinginductivelycoupledCl2/ArandCl2/BCl3plasmas.JVacSciTechnolA,1998,16(3):1478[11]ButtariD,ChiniA,PalaciosT,etal.OriginofetchdelaytimeinCl2dryetchingofAlGaN/GaNstructures.ApplPhysLett,2003,83(23):4779[12]ShenL,PalaciosT,PoblenzC,etal.UnpassivatedhighpowerdeeplyrecessedGaNHEMTswithfluorine2plasmasurfacetreatment.IEEEElectronDeviceLett,2006,27(4):214[13]HinokiA,HatayaK,MiyamotoH,etal.InfluenceofdryetchingonnitridesemiconductorSchottkycharacteristics.The2007InternationalMeetingforFutureofElectronDevices,Kansai(IMFEDK),2004,PB7:71087111:AlGaN/GaNHEMTEffectofPlasmaDryEtchingonGateLeakageofRecessedAlGaN/GaNHEMTs3LiChengzhan­,PangLei,LiuXinyu,HuangJun,LiuJian,ZhengYingkui,andHeZhijing(InstituteofMicroelectronics,ChineseAcademyofSciences,Beijing100029,China)Abstract:Themechanismforincreasinggateleakagecurrentinrecessed2gateAlGaN/GaNHEMTs,whicharefabricatedsuccessfullybyplasmadryetching,isinvestigated.ComparedwithconventionalplanarFETs,thegateleakagecurrentoftherecessed2gateAlGaN/GaNHEMTsincreasesby10times,andthebreakdownvoltagedecreasestosomeextent.AFMandXPSareemployedtomeasuretheAlGaNsurfacebeforeandafteretching.TheAlGaNsurfacebecomesrougher,andevensomeprotuberanceslikeawlappearduringdryetching.ThusthecontactareabetweenthemetalandthesemiconductorincreasesfortherougherAlGaNsurface.Ontheotherhand,someNvacanciesgenerateplasmabombardingduringdryetching.TheNvacancies,whichenhancethetunnelingeffectandreducetheSchottkybarrierheight,areregardedasn2typedopedintheetchedAlGaNsurface.Alltheseexperimentsindicatethatthesignificantincreaseinthegateleakagecurrentisduetothein2creasedroughnessandtheappearanceoftheseNvacanciesintheAlGaNsurface.Keywords:plasmadryetching;recessed2gate;gateleakage;NvacanciesEEACC:2570ArticleID:025324177(2007)11217772053Project