EE2411UC Berkeley EE241 B. NikolicEE241 - Spring 2002Advanced Digital Integrated CircuitsLecture 3MOS Models, Technology ScalingUC Berkeley EE241 B. NikolicDigital Gate• Basic Properties• Functionality• Robustness• ∆ Swing, Noise margins• Delay• tPLH, t PHL• Power, energy consumption• Power-Delay-Product• Area•DensityEE2412UC Berkeley EE241 B. NikolicBasic CMOS GateProperties• Output levels determined by supply• Large noise margins• Performance loss at low voltagesUC Berkeley EE241 B. NikolicMOS Transistor as a Switch Discharging a capacitor• Can solve:()DSDDvii=dtdVCiDSD=EE2413UC Berkeley EE241 B. NikolicMOS Transistor as a SwitchTraversed pathUC Berkeley EE241 B. NikolicMOS Transistor as a SwitchSolving the integral:Averaging resistances:EE2414UC Berkeley EE241 B. NikolicEquivalent ResistanceW/L=1, L=0.25UC Berkeley EE241 B. NikolicCMOS PerformancePropagation delay:()LeqnpHLCRt 2ln=()LeqppLHCRt 2ln=Short channel Long channel)(DDeqVfR≠DDeqVR1∝TDDVV>>forEE2415UC Berkeley EE241 B. NikolicMOS CapacitancesCGSO= CGDO= CoxxdW= CoWUC Berkeley EE241 B. NikolicGate CapacitanceEE2416UC Berkeley EE241 B. NikolicChannel CapacitanceUC Berkeley EE241 B. NikolicMOS CapacitancesEE2417UC Berkeley EE241 B. NikolicPower DissipationUC Berkeley EE241 B. NikolicScaling Models• Full Scaling (Constant Electrical Field)• Fixed Voltage Scaling• General Scalingideal model — dimensions and voltage scaletogether by the same factor Smost common model until recently —only dimensions scale, voltages remain constantmost realistic for today’s situation —voltages and dimensions scale with different factorsEE2418UC Berkeley EE241 B. NikolicConstant Field ScalingCourtesy of IEEE Press, New York.  2000UC Berkeley EE241 B. Nikolic2-D Effects in a Short-Channel MOSFETCourtesy of IEEE Press, New York.  2000EE2419UC Berkeley EE241 B. NikolicScaling Models – Long ChannelUC Berkeley EE241 B. NikolicScaling Models – Short ChannelEE24110UC Berkeley EE241 B. NikolicCurrent Scaling Scenario[Davari95]Note: Delays scale similarly if wp, wnand Cwirescale in the same way.UC Berkeley EE241 B. NikolicSupply and Threshold ScalingCourtesy of IEEE Press, New York.  2000EE24111UC Berkeley EE241 B. NikolicIssues in ThresholdsUC Berkeley EE241 B. NikolicMOSFET CurrentCourtesy of IEEE Press, New York.  2000EE24112UC Berkeley EE241 B. NikolicPower vs. DelayCourtesy of IEEE Press, New York.  2000UC Berkeley EE241 B. NikolicPower vs. DelayCourtesy of IEEE Press, New York.  2000101-stage ring oscillator10% in delay increase saves 40% in power using supply scalingEE24113UC Berkeley EE241 B. NikolicIssues in Scaling•Reliability:Break down, hot electron effects•Cost•Density, Speed, PowerTwo Scenario’s are emerging:•High speed scenario•Low power scenariodifferent voltage scaling trajectoriesUC Berkeley EE241 B. NikolicHigh-Speed vs. Low-Power Scenarios[Davari95]EE24114UC Berkeley EE241 B. NikolicGate TunnelingCourtesy of IEEE Press, New York.  2000UC Berkeley EE241 B. NikolicCMOS Cross SectionCourtesy of IEEE Press, New York.  2000EE24115UC Berkeley EE241 B. NikolicEvolution of Channel DopingCourtesy of IEEE Press, New York.  2000UC Berkeley EE241 B. NikolicThe Low-Power ScenarioReducing VT improves performance (at lower voltages)0.25µm CMOS delay versus threshold voltage [Davari95]EE24116UC Berkeley EE241 B. NikolicWeak InversionUC Berkeley EE241 B. NikolicExampleEE24117UC Berkeley EE241 B. NikolicSub-threshold SlopeAs a function of channel lengthCourtesy of IEEE Press, New York.  2000UC Berkeley EE241 B. NikolicSubthreshold SlopeCourtesy of IEEE Press, New York.  2000A case for low-temperature CMOSEE24118UC Berkeley EE241 B. NikolicImpact of sub-threshold currentsUC Berkeley EE241 B. NikolicThreshold Roll-offCourtesy of IEEE Press, New York.  2000EE24119UC Berkeley EE241 B. NikolicInterconnectUC Berkeley EE241 B. NikolicInterconnect ScalingCourtesy of IEEE Press, New York.  2000EE24120UC Berkeley EE241 B. NikolicAdding Layers of InterconnectCourtesy of IEEE Press, New York.  2000UC Berkeley EE241 B. NikolicExample: Intel 0.25 micron Process5 metal layersTi/Al - Cu/Ti/TiNPolysilicon