Chapter-7-Metal–Oxide–Semiconductor-Field-Effect-Transistor-Additional-Concepts.ppt

Chapter 1 Chapter 1 1 1College of Electronic Science and EngineeringNanjing University of Posts and Telecommunications Semiconductor Devices PhysicsSemiconductor Devices PhysicsChapter 7:MetalOxideSemiconductor Field-Effect Transistor:Additional ConceptsChapter 1 Chapter 1 2 2College of Electronic Science and EngineeringNanjing University of Posts and Telecommunications Semiconductor Devices Physics7.1 MOSFET Scaling 3127.1.1 Constant-Field Scaling 3127.1.2 Threshold VoltageFirst Approximation 3137.1.3 Generalized Scaling 3147.2 Nonideal Effects 3157.2.1 Subthreshold Conduction 3157.2.2 Channel Length Modulation 3187.2.3 Mobility Variation 3217.2.4 Velocity Saturation 3247.3 Threshold Voltage Modifications 3267.3.1 Short-Channel Effects 3277.3.2 Narrow-Channel Effects 3317.3.3 Substrate Bias Effects 3337.4 Additional Electrical Characteristics 3357.4.1 Oxide Breakdown 3357.4.2 Near Punch-Through or Drain-Induced Barrier Lowering 3357.4.3 Hot Electron Effects 3377.4.4 Threshold Adjustment by Ion Implantation 3387.5 Device Fabrication Techniques:Specialized Devices 3417.5.1 Lightly Doped Drain Transistor 3427.5.2 The MOSFET on Insulator 3437.5.3 The Power MOSFET 3457.5.4 MOS Memory Device 3487.6 Summary MetalOxideSemiconductor Field-Effect Transistor:Additional ConceptsChapter 1 Chapter 1 3 3College of Electronic Science and EngineeringNanjing University of Posts and Telecommunications Semiconductor Devices Physics7.1 MOSFET Scaling 7.1.1 Constant-Field Scaling Table 7.1 P314Chapter 1 Chapter 1 4 4College of Electronic Science and EngineeringNanjing University of Posts and Telecommunications Semiconductor Devices Physics7.1 MOSFET Scaling7.1.2 Threshold VoltageFirst Approximation Chapter 1 Chapter 1 5 5College of Electronic Science and EngineeringNanjing University of Posts and Telecommunications Semiconductor Devices Physics When the device size reduction,must minimize short-channel effects,to ensure proper device characteristics and circuit operation.It needs some criteria to design the scaling down of devices,a brief method of maintaining long-channel characteristics is scaling down all the sizes and voltages,the scaling down factor is(1)，so,the internal electric field will remain as long-channel MOSFET，this method is called fixed electric field scaling down rule(CE).7.1.3 Generalized Scaling Problems of constant electric field lawsqReduction of the threshold voltage can not be too smallqDepletion width of source and drain can not be scaled downqChanges of power supply voltage standard will bring great inconvenience7.1 MOSFET ScalingChapter 1 Chapter 1 6 6College of Electronic Science and EngineeringNanjing University of Posts and Telecommunications Semiconductor Devices Physicsq laws of constant-voltage scaling down(Referred to as CV law)lMaintain the power supply voltage Vds and threshold voltage Vth the same,other parameters scaling downlThe improvement of circuit performance scaled down by CV law is far less well than that scaled down by CE law,and the use of CV will greatly enhance the electric field in the channellCV law is generally applied to the devices whos channel length is more than more than 1 m,it does not apply to a shorter channel length device。7.1 MOSFET ScalingChapter 1 Chapter 1 7 7College of Electronic Science and EngineeringNanjing University of Posts and Telecommunications Semiconductor Devices Physics7.2 Nonideal Effects 7.2.1 Subthreshold Conduction Chapter 1 Chapter 1 8 8College of Electronic Science and EngineeringNanjing University of Posts and Telecommunications Semiconductor Devices PhysicsCross section along channel length of n-channel MOSFET.Energy-band diagrams along channel length at(b)accumulation,(c)weak inversion,and(d)inversion.7.2 Nonideal Effects Chapter 1 Chapter 1 9 9College of Electronic Science and EngineeringNanjing University of Posts and Telecommunications Semiconductor Devices PhysicsSubthreshold current-voltage characteristics for several values of substrate voltage.7.2 Nonideal Effects Chapter 1 Chapter 1 1010College of Electronic Science and EngineeringNanjing University of Posts and Telecommunications Semiconductor Devices Physics7.2.2 Channel Length Modulation 7.2 Nonideal Effects Chapter 1 Chapter 1 1111College of Electronic Science and EngineeringNanjing University of Posts and Telecommunications Semiconductor Devices Physics7.2 Nonideal Effects Chapter 1 Chapter 1 1212College of Electronic Science and EngineeringNanjing University of Posts and Telecommunications Semiconductor Devices Physics7.2.3 Mobility Variation 7.2 Nonideal Effects Chapter 1 Chapter 1 1313College of Electronic Science and EngineeringNanjing University of Posts and Telecommunications Semiconductor Devices Physics7.2 Nonideal EffectsMeasured inversion layer electron mobility versus electric field at the inversion layerChapter 1 Chapter 1 1414College of Electronic Science and EngineeringNanjing University of Posts and Telecommunications Semiconductor Devices Physics7.2.4 Velocity Saturation 7.2 Nonideal EffectsChapter 1 Chapter 1 1515College of Electronic Science and EngineeringNanjing University of Posts and Telecommunications Semiconductor Devices Physics7.3 Threshold Voltage Modifications 7.3.1 Short-Channel Effects Long n-channel MOSFETChapter 1 Chapter 1 1616College of Electronic Science and EngineeringNanjing University of Posts and Telecommunications Semiconductor Devices PhysicsShort n-channel MOSFET7.3 Threshold Voltage Modifications Chapter 1 Chapter 1 1717College of Electronic Science and EngineeringNanjing University of Posts and Telecommunications Semiconductor Devices Physics7.3 Threshold Voltage ModificationsChapter 1 Chapter 1 1818College of Electronic Science and EngineeringNanjing University of Posts and Telecommunications Semiconductor Devices Physics7.3 Threshold Voltage ModificationsThreshold voltage versus channel length for various substrate dopingsThreshold voltage versus channel length for two values of drain-to-sourec and body-to-soured voltage.Chapter 1 Chapter 1 1919College of Electronic Science and EngineeringNanjing University of Posts and Telecommunications Semiconductor Devices Physics When the channel edge effect can not be neglected,with the reduction of the channel,the threshold voltage of n channel MOSFET is not as positive as it were,while for a p channel MOSFET it is not negative as it were，the following figure shows the down phenomenon of VT when VDS=0.05 the threshold voltage drop in linear region(Vth roll-off)02.04.06.02.0-4.0-02.04.06.0V05.0DS=VV8.1DS=VNMOSPMOSV05.0DS-=VV8.1DS-=V02.04.06.02.0-4.0-02.04.06.002.04.06.02.0-4.0-02.04.06.0V05.0DS=VV8.1DS=VNMOSPMOSV05.0DS-=VV8.1DS-=Vm/m栅LV/TV7.3 Threshold Voltage ModificationsChapter 1 Chapter 1 2020College of Electronic Science and EngineeringNanjing University of Posts and Telecommunications Semiconductor Devices Physics7.3.2 Narrow-Channel Effects7.3 Threshold Voltage ModificationsChapter 1 Chapter 1 2121College of Electronic Science and EngineeringNanjing University of Posts and Telecommunications Semiconductor Devices Physics7.3 Threshold Voltage ModificationsChapter 1 Chapter 1 2222College of Electronic Science and EngineeringNanjing University of Posts and Telecommunications Semiconductor Devices Physics7.3.3 Substrate Bias Effects 7.3 Threshold Voltage ModificationsChapter 1 Chapter 1 2323College of Electronic Science and EngineeringNanjing University of Posts and Telecommunications Semiconductor Devices Physics7.3 Threshold Voltage ModificationsChapter 1 Chapter 1 2424College of Electronic Science and EngineeringNanjing University of Posts and Telecommunications Semiconductor Devices Physics7.4 Additional Electrical Characteristics 7.4.1 Oxide Breakdown Chapter 1 Chapter 1 2525College of Electronic Science and EngineeringNanjing University of Posts and Telecommunications Semiconductor Devices Physics DIBL will form the leakage path on the interface of SiO2/Si,when the drain voltage is large enough,there may have significant leakage current flows from source to drain through the ontology flow of short channel MOSFET,this can be attributed to the width of drain junctions depletion region will expanse with the increase of drain voltage.7.4.2 Near Punch-Through or Drain-Induced Barrier Lowering7.4 Additional Electrical Characteristics Chapter 1 Chapter 1 2626College of Electronic Science and EngineeringNanjing University of Posts and Telecommunications Semiconductor Devices PhysicsIn short channel MOSFET,the sum of depletion region width of source junction and drain junction is same to channel length.When the drain voltage increases,depletion region of drain junction will gradually integrate with the source,so a lot of drain current will flow from the drain into the source through the ontology flow,so,the devices will have a very high leakage current.7.4 Additional Electrical Characteristics Chapter 1 Chapter 1 2727College of Electronic Science and EngineeringNanjing University of Posts and Telecommunications Semiconductor Devices Physics7.4 Additional Electrical CharacteristicsIt also shows that the effect of ontology penetrating is significant,gate can no longer shut down the devices completely,and can no longer control the drain current.High leakage current will limit the work of short-channel MOSFET.Chapter 1 Chapter 1 2828College of Electronic Science and EngineeringNanjing University of Posts and Telecommunications Semiconductor Devices Physics7.4.3 Hot Electron Effects 7.4 Additional Electrical CharacteristicsChapter 1 Chapter 1 2929College of Electronic Science and EngineeringNanjing University of Posts and Telecommunications Semiconductor Devices Physics7.4.4 Threshold Adjustment by Ion Implantation 7.4 Additional Electrical CharacteristicsChapter 1 Chapter 1 3030College of Electronic Science and EngineeringNanjing University of Posts and Telecommunications Semiconductor Devices Physics7.5 Device Fabrication Techniques:Specialized Devices 7.5.1 Lightly Doped Drain Transistor Chapter 1 Chapter 1 3131College of Electronic Science and EngineeringNanjing University of Posts and Telecommunications Semiconductor Devices Physics7.5 Device Fabrication Techniques:Specialized Devices Chapter 1 Chapter 1 3232College of Electronic Science and EngineeringNanjing University of Posts and Telecommunications Semiconductor Devices Physics7.5.2 The MOSFET on Insulator 7.5 Device Fabrication Techniques:Specialized DevicesChapter 1 Chapter 1 3333College of Electronic Science and EngineeringNanjing University of Posts and Telecommunications Semiconductor Devices Physics7.5 Device Fabrication Techniques:Specialized DevicesKink effectChapter 1 Chapter 1 3434College of Electronic Science and EngineeringNanjing University of Posts and Telecommunications Semiconductor Devices Physics7.5.3 The Power MOSFET 7.5 Device Fabrication Techniques:Specialized DevicesChapter 1 Chapter 1 3535College of Electronic Science and EngineeringNanjing University of Posts and Telecommunications Semiconductor Devices Physics7.5 Device Fabrication Techniques:Specialized DevicesA HEXFET structureChapter 1 Chapter 1 3636College of Electronic Science and EngineeringNanjing University of Posts and Telecommunications Semiconductor Devices Physics7.5 Device Fabrication Techniques:Specialized DevicesTypical drain-to-source resistance versus drain current characteristics of a MOSFET.Chapter 1 Chapter 1 3737College of Electronic Science and EngineeringNanjing University of Posts and Telecommunications Semiconductor Devices Physics7.5 Device Fabrication Techniques:Specialized DevicesChapter 1 Chapter 1 3838College of Electronic Science and EngineeringNanjing University of Posts and Telecommunications Semiconductor Devices Physics7.5.4 MOS Memory Device 7.5 Device Fabrication Techniques:Specialized DevicesChapter 1 Chapter 1 3939College of Electronic Science and EngineeringNanjing University of Posts and Telecommunications Semiconductor Devices Physics7.6 Summary Constant-Field Scaling Channel length scalingSubthreshold current Subthreshold conductionChannel Length Modulation Short channel effectSurface scattering effect Effective surface electric fieldVelocity saturation Cutoff frequencyCharge sharing Substrate bias effectsOxide breakdown Hot electron(effects)Threshold adjustment Channel resistanceChapter 1 Chapter 1 4040College of Electronic Science and EngineeringNanjing University of Posts and Telecommunications Semiconductor Devices Physics