半导体器件物理(刘洋)MOSFET-part6

DevicestructurePolysiliconGateChanneldopingprofileFINStructureMemorydeviceDevicestructuresChanneldopingprofile-P-dopingatsurface:mobilityconsideration-Pdopingformiddlelayer:punchthrough-P-dopingindeeplayer:reducingjunctioncapacitance(subthresholdswing/slope)DevicestructureDevicestructureDevicestructureDevicestructureDevicestructureDevicestructureDevicestructureDevicestructureFINstructure:3DstructureFabricationdifficultiesNonvolatilememoryNonvolatilememoryNonvolatilememoryNonvolatilememoryNonvolatilememoryNonvolatilememoryNonvolatilememoryWhatispopularlyusedmemory?FlashmemorydeviceNonvolatilememories(EEPROMs&Flash)Applicationsfordata&codestorage1)Consumerelectronics2)Automotive3)Militaryandaerospaceequipment4)Medicalinstrumentsandpatientdatastorage5)IndustrialinstrumentsFlashmemoryConventionalfloating-gateflashmemoryMostofflashmemoryproductsarebasedonfloating-gatetechnologyMarketisdominatedbygiantslikeSamsung,Sandisc,Toshiba,etc.CurrentroadmapforNANDflashProcesstechnology130nm90nm65nm45nm32nm22nmFloating-gatetechnologywillrunoutofstreamfor45nmandbeyondduetoproblemsinvoltagescaling,reliability,fabricationcost,etc.Processtechnology130nm90nm65nm45nm32nm22nmSolid-SateStorage*MarketShare*includedFlashCard&USBFlashDriveNonvolatilememoryDifferentdevicestructuresSimilarworkingmechanismNonvolatilememoryVtshiftformemorystatetransitionMeasurementatVds=0.1VGateVoltage,Vg(V)01234DrainCurrent(A)01020304050Program:Vg=+10VErase:Vg=-10VVtdQNonvolatilememoryOneofworkingmechanisms:HotcarrierinjectionWhatcanbetheothermechanism?NonvolatilememoryBanddiagramsNonvolatilememoryTheothermechanism:Fowler-NordheimtunnelingNonvolatilememoryCHEFowler-Nordheim(FN)ProgrammingmechanismsCHEFN26ChargeeraseFowler-NordheimTunneling–Electronpasssteepenergybandthroughtheoxide-VG0V0VNonvolatilememoryNonvolatilememoryVtshiftProgramming/erasingcapabilityMeasurementatVds=0.1VGateVoltage,Vg(V)01234DrainCurrent(A)01020304050Program:Vg=+10VErase:Vg=-10VCycles100101102103104105106ThresholdVoltage(V)1.41.61.82.02.22.42.62.83.0RoomTemperatureEraseProgramNonvolatilememoryRetentiontimeHowlongdatacanbemaintainedinmemory?Time(s)100101102103104105106107108109ThresholdVoltage(V)1.41.61.82.02.22.42.62.83.010-yearsRoomTemperatureProgramEraseNonvolatilememoryLimitation高速的擦写、低功耗及低生产成本的要求薄的隧穿氧化层；长数据保持时间、耐擦写特性及可靠性要求比较厚的隧穿氧化层妥协的结果是隧穿氧化层要超过8nmGateVoltage(V).51.01.52.02.53.0Capacitance(pF)123456789VirginAfterapplicationof-3Vfor10sW:L=10m:2mRoomTemperatureVds=0.1VGateVoltage(V)012345DrainCurrent(A)10-1510-1410-1310-1210-1110-1010-910-810-710-610-510-410-310-2Erase,Vg=-12Vfor1msWrite,Vg=+12Vfor1ms30NonvolatilememoryHowcanimprovetheperformance?Nonvolatilememory•Advantage–NosingledefectissueandGCRissue–Furtherscaledown,highdensity,Itisforecastedassolutionbelow45nm–Highspeedandlowpower–Multi-bitcellpossibleNonvolatilememoryTwobitmemorycanbeachievedbyCHEbaseondiscretechargeinjection34Nonvolatilememory纳米晶体存储器件硅纳米晶体由LPCVD或离子束合成100%CMOS工艺兼容写入时间=100ns,写入电压~10V可擦写次数1百万次数据保持时间10年*当前普通的浮栅工艺器件多晶硅浮栅由CVD生长.CMOS工艺写入时间=1ms,写入电压~17V可擦写次数=104-105次数据保持时间大约10年*S.I.Association,InternationalTechnologyRoadmapforSemiconductors,QuantizationofchargeSmalldimensionoftheislandSDGCC+C+C21002qkTCTotalcapacitanceToaddoneelectronorremoveoneelectronto/fromtheislandSingleElectronTransistorCurrent-VoltagecharacteristicsApplicationsMulti-bitmemorydevice