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CMOS Fabrication Technology CMOS Fabrication Technology and Design Rulesand Design Rules

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CMOS Inverter CMOS Inverter

CMOS Inverter

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CMOS Noise MarginsCMOS Noise Margins

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CMOS TimingsCMOS Timings

Tp = (TpHL + TpLH )/2Propagation Time:

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CMOS Transient ResponseCMOS Transient Response

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MOS TransistorMOS Transistor

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MOS CurrentMOS Current

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MOS Current EquationsMOS Current Equations

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Velocity SaturationVelocity Saturation At a certain electric field, the velocity of carriers does not increase but tends to be constant.

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Velocity SaturationVelocity Saturation

Short channel devices reach velocity saturation earlier than long channel ones.

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Threshold VoltageThreshold Voltage

The minimum voltage when the device turns on is called The minimum voltage when the device turns on is called VVthth

For NMOS: VFor NMOS: Vgg > V > Vthth

For PMOS: VFor PMOS: Vgg < V < Vthth

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Body EffectBody Effect

Threshold voltage increases if the body of PMOS is not connected to Vdd or Vss for NMOS.

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Transistor LeakageTransistor Leakage

Leakage current is exponential with Vgs.

Also called Subthreshold behavior

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Leakage CurrentLeakage CurrentSubthreshold current can be calculated by:

Increasing Vth decreases Leakage current but slows down the device

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Leakage ComponentsLeakage Components1. pn junction reverse bias current2. Weak inversion3. Drain-induced barrier lowering (DIBL)4. Gate-induced drain leakage (GIDL)5. Punchthrough6. Narrow width effect7. Gate oxide tunneling8. Hot carrier injection

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CMOS FabricationCMOS Fabrication

Both NMOS and PMOS to be built on the same chip Both NMOS and PMOS to be built on the same chip substratesubstrate

To create both devices, special regions called wells or To create both devices, special regions called wells or tubs must be created in substratetubs must be created in substrate

A p-well is created in n-type substrate and an n-well is A p-well is created in n-type substrate and an n-well is created in p-type substrate created in p-type substrate