电子器件场效应晶体管.ppt

0102Effectsofrealsurfacesalkalimetalions碱金属离子sodium(Na+)ion钠离子mobilecharge可动电荷trappedcharge陷阱电荷interfacecharge界面电荷fixedcharge固定电荷effectivepositivecharge有效正电荷heavilydopedpoly-silicon重掺杂多晶硅

MOSStructurePoly-silicon-OSStructureIdealMOScapacitanceRealSurfaceEffects:WorkfunctiondifferenceinterfacechargeNon-idealcapacitance

workfunctiondifferencesemiconductoroxiden+polysilicon(多晶硅)?ms=?m-?sn+poly-nSin+poly-pSi

1Ideal2Non-ideal

(EFm-EFs)=(q?s-q?m)V=?s-?mVG=VFB(平带电压)=-V=?m-?s=?ms

InterfacechargeGenerally,therearefourtypesofchargesinapracticalMOSstructure.MobileionicchargeQm可动离子电荷OxidetrappedchargeQot氧化物陷阱电荷OxidefixedchargeQf氧化物固定电荷InterfacetrapchargeQit界面陷阱电荷0102

IdealInterfacecharge

Qi

Effectsofrealsurface

6.4.4ThresholdvoltageToachievetheflatband01Toaccommodatethedepletioncharge02Toinducetheinvertedregion03

Qd=-qNaWm(nchannel/P-sub)Qd=qNdWm(pchannel/N-sub)Whenisthethresholdvoltageofp-channelMOSFETgreaterthan0?Howtodo?

flatbandvoltage

2）thresholdvoltage

depletionmode01becauseVT002

(4)MOSCapacitor(ideal)Capacitance-voltagecharacteristics(电容电压特性）CiCsBecauseCsisdependingonVG,theoverallcapacitancebecomesvoltagedependent.

CiCsTomeasurethecapacitance,wemustsuperposethesmalla-csignaltothevoltage.ThatisVG=V+dVG.HeredVGusedtomeasurethecapacitancewillcausethesmallchargechangeoftheMOScapacitorHighfrequency

6.4.5MOScapacitance-voltageanalysisVT~SubstrateDopingTypeC-VGPerformance~SubstrateDopingTypeTomeasurethedopingdensityofsubstrateTomeasuretheinterfacestateTomeasurethemobilechargewithintheoxide

Tomeasurethecapacitance,wemustsuperposethesmalla-csignaltothevoltage.ThatisVG=V+dVG.HeredVGusedtomeasurethecapacitancewillcausethesmallchargechangeoftheMOScapacitor(1)Tomeasurethewidthofoxidelayer,dopingdensityofsubstrate,VFB