Device Models PN Diode, MOSFET - University of...

Device Models Device Models ((PN Diode, MOSFET PN Diode, MOSFET ))

Instructor: Steven P. Levitan steve@ece.pitt.eduTA: Gayatri Mehta, José MartínezBook: Digital Integrated Circuits: A Design Perspective; Jan RabaeyLab Notes: Handed outhttp://infopad.EECS.Berkeley.EDU/~icdesign/

ECE 1192 ©, 2006, Steven Levitan, University of Pittsburgh

Goal of this chapterGoal of this chapterPresent intuitive understanding of device operationIntroduction of basic device equationsIntroduction of models for manual analysisIntroduction of models for SPICE simulationAnalysis of secondary and deep-sub-micron effectsFuture trends

The DIODEThe DIODE

B A SiO2Al

Cross-section of pn-junction in an IC process

One-dimensionalrepresentation diode symbol

Mostly occurring as parasitic element in Digital ICs

Diodes in a CMOS circuitDiodes in a CMOS circuit

Depletion Region FormationDepletion Region Formationhole diffusion

electron diffusion

hole driftelectron drift

ChargeDensity

Distancex+

ElectricalxField

PotentialV

(a) Current flow.

(b) Charge density.

(c) Electric field.

(d) Electrostaticpotential.

Formation and characteristics of a Formation and characteristics of a pnpn junctionjunction

Forward BiasForward Bias

-W1 W20p n

n-regionp-region

diffusion

Typically avoided in Digital ICs

Reverse BiasReverse Bias

-W1 W20n-regionp-region

diffusion

The Dominant Operation Mode

Diode Current Diode Current –– a Simple Modela Simple Model

Models for Manual AnalysisModels for Manual Analysis

ID = IS(eVD/φT – 1)+

(a) Ideal diode model (b) First-order diode model

PN Junction Diode DC Model PN Junction Diode DC Model ((DetailsDetails))

Thermal VoltageФT = kT/q ≈ 0.0259 V ( 300 ˚K)

k Boltzmann constant (1.38066x10-23 J/K)T Absolute temperature (˚K) q Electron charge (1.60218x10-19 C)

Is In practice, this term has to be obtained by characterization since it is highly dependent on doping concentration, dimension, operative temperature etc.

PN Junction: Dynamic EffectsPN Junction: Dynamic Effects

Primary effectsJunction CapacitanceDiffusion Capacitance

Secondary EffectsAvalanche Breakdown

Junction CapacitanceJunction Capacitance

Diffusion CapacitanceDiffusion Capacitance

Integrated Diode ModelIntegrated Diode Model

SPICE ParametersSPICE Parameters

The MOS TransistorThe MOS Transistor

Polysilicon Aluminum

Controlling current flow in an Controlling current flow in an nFETnFET..

Controlling current flow in an Controlling current flow in an pFETpFET..

What is a Transistor?What is a Transistor?

VGS ≥ VT

RonS D

A Switch!

An MOS Transistor

MOS Transistors MOS Transistors -- Types and SymbolsTypes and Symbols

NMOS Enhancement NMOS Depletion

PMOS Enhancement

NMOS withBulk Contact

MOS Transistors MOS Transistors –– Regions Transitions Regions Transitions

p-substrate

DepletionRegion

n-channel

Threshold Voltage: ConceptThreshold Voltage: Concept

Threshold Voltage Threshold Voltage -- DerivationDerivation

The Body EffectThe Body Effect

-2.5 -2 -1.5 -1 -0.5 00.4

2-input NAND gate

Drain of N1 is Source of N2 VSB of N2 >= 0

MOS Transistors MOS Transistors –– Operating regions Operating regions

Transistor in LinearTransistor in Linear

p-substrate

V(x) +–

MOS transistor and its bias conditions

p-substrate

V(x) +–

Linear Region Linear Region VVgsgs>>VVtt & & VVgdgd>>VVtt

Positive Charge on Gate:Channel exists, Current Flows

since Vds > 0Ids = k’(W/L)((Vgs-Vt)Vds-Vds

R= 1/(k’(W/L)(Vgs-Vt))

Transistor in SaturationTransistor in Saturation

VDS > VGS - VT

VGS - VT+-

Pinch-off

VDS > VGS - VT

VGS - VT+-

Saturation: Saturation: VVgsgs>>VVtt & & VVgdgd<<VVtt

Positive Charge on Gate:Channel exists, Current Flows

since Vds > 0But: channel is “pinched off”

Ids = (k’/2)(W/L)(Vgs-Vt)2

CurrentCurrent--Voltage RelationsVoltage RelationsA good A good olol’’ transistortransistor

QuadraticRelationship

0 0.5 1 1.5 2 2.50

VDS (V)

)VGS= 2.5 V

VGS= 2.0 V

VGS= 1.5 V

VGS= 1.0 V

Resistive Saturation

VDS = VGS - VT

CurrentCurrent--Voltage RelationsVoltage RelationsLongLong--Channel DeviceChannel Device

Cut-off (VGS – VT < 0) “no current” (not really)

Computed CurvesComputed Curves

Vgs = 5v

Vgs = 4.5v

Vgs = 4.0v

Linear Resistor

CurrentCurrent--Voltage RelationsVoltage RelationsThe DeepThe Deep--Submicron EraSubmicron Era

LinearRelationship

VDS (V)0 0.5 1 1.5 2 2.5

2.5x 10

VGS= 2.5 V

VGS= 2.0 V

VGS= 1.5 V

VGS= 1.0 V

Early Saturation

Velocity SaturationVelocity Saturation

ξ (V/µm)ξc = 1.5

υsat = 105

( m/ s

Constant mobility (slope = µ)

Constant velocity

PerspectivePerspective

IDLong-channel device

Short-channel device

VDSVDSAT VGS - VT

VGS = VDD

IIDD versus Vversus VGSGS

0 0.5 1 1.5 2 2.50

VGS(V)

0 0.5 1 1.5 2 2.50

2.5x 10

VGS(V)

quadratic

linear

Long Channel Short Channel

IIDD versus Vversus VDSDS

VDS(V)0 0.5 1 1.5 2 2.50

2.5x 10

VGS= 2.5 V

VGS= 2.0 V

VGS= 1.5 V

VGS= 1.0 V

0 0.5 1 1.5 2 2.50

6x 10-4

VDS(V)

VGS= 2.5 V

VGS= 2.0 V

VGS= 1.5 V

VGS= 1.0 V

Resistive Saturation

VDS = VGS - VT

Long Channel Short Channel

A unified modelA unified modelfor manual analysisfor manual analysis

Simple Model versus SPICE Simple Model versus SPICE

0 0.5 1 1.5 2 2.50

2.5x 10

VDS (V)

VelocitySaturated

Linear

Saturated

VDSAT=VGT

VDS=VDSAT

VDS=VGT

A PMOS TransistorA PMOS Transistor

-2.5 -2 -1.5 -1 -0.5 0-1

VDS (V)

Assume all variablesnegative!

VGS = -1.0V

VGS = -1.5V

VGS = -2.0V

VGS = -2.5V

Transistor Model Transistor Model for Manual Analysisfor Manual Analysis

The Transistor as a SwitchThe Transistor as a Switch

VGS ≥ VT

RonS D

VGS = VD D

VDD/2 VDD

0.5 1 1.5 2 2.50

Saturation EffectsSaturation Effects

Which is the resistor?

Discharge of 1pf capacitor, with Vgs of 3,4,5 volts. Also, 12k resistor.

MOS CapacitancesMOS CapacitancesDynamic BehaviorDynamic Behavior

Dynamic Behavior of MOS TransistorDynamic Behavior of MOS Transistor

CGDCGS

CSB CDBCGB

Physical visualization of FET Physical visualization of FET capacitancescapacitances

MOS Capacitances Behavior !MOS Capacitances Behavior !

The Gate Capacitance in an nThe Gate Capacitance in an n--channel channel MOSFETMOSFET

The Gate Capacitance The Gate Capacitance

Cross section

Gate oxide

Polysilicon gate

Top view

Gate-bulkoverlap

Source

Gate CapacitanceGate Capacitance

Gate Capacitance Gate Capacitance –– BehaviorBehavior

CGCS D

Cut-off Resistive Saturation

Most important regions in digital design: saturation and cut-off

WLCox2

2WLCox3

VDS /(VGS-VT)

CGCS = CGCDCGC B

WLCox2

Capacitance as a function of VGS(with VDS = 0)

Capacitance as a function of the degree of saturation

Gate Capacitance Gate Capacitance –– BehaviorBehavior

Measuring the Gate CapMeasuring the Gate Cap

2 1.52 1 2 0.5 0

103 102 16

VGS (V)

0.5 1 1.5 22 2

Diffusion CapacitanceDiffusion Capacitance

Bottom

Side wall

Side wallChannel

SourceND

Channel-stop implantNA1

Substrate NA

Junction capacitances in a MOSFETJunction capacitances in a MOSFET

Calculation of the FET junction Calculation of the FET junction capacitancecapacitance

Junction capacitance variation with Junction capacitance variation with reverse voltagereverse voltage

Final construction of the Final construction of the nFETnFET RC RC modelmodel

Capacitances in 0.25 Capacitances in 0.25 μμm CMOS m CMOS processprocess

Values for a Typical Device:

The SubThe Sub--Micron MOS TransistorMicron MOS Transistor

Threshold VariationsSub-threshold ConductionParasitic Resistances

Threshold VariationsThreshold Variations

Long-channel threshold Low VDS threshold

Threshold as a function of the length (for low VDS)

Drain-induced barrier lowering (for low L)

SubSub--Threshold Threshold IIDD vsvs VVGSGS

VDS from 0 to 0.5V

⎟⎟⎠

⎞⎜⎜⎝

⎛−=

eeII 10

Log Scale

SubSub--Threshold Threshold IIDD vsvs VVDSDS

( )DSkT

D VeeIIDSGS

⋅+⎟⎟⎠

⎞⎜⎜⎝

⎛−=

−λ110

VGS from 0 to 0.3V

Linear scale

Summary of MOSFET Operating Summary of MOSFET Operating RegionsRegions

Strong Inversion VGS > VTLinear (Resistive) VDS < VDSAT

Saturated (Constant Current) VDS ≥VDSAT

Weak Inversion (Sub-Threshold) VGS ≤VTExponential in VGS with linear VDS dependence

Parasitic ResistancesParasitic Resistances

Draincontact

Polysilicon gate

VGS,eff

LatchupLatchup

(a) Origin of latchup (b) Equivalent circuit

Rpsubs

Rnwell p-source

n-source

n+ n+p+ p+ p+ n+

p-substrateRpsubs

Rnwell

n-well

SPICE MODELSSPICE MODELS

Level 1: Long Channel Equations - Very Simple

Level 2: Physical Model - Includes VelocitySaturation and Threshold Variations

Level 3: Semi-Emperical - Based on curve fittingto measured devices

Level 4 (BSIM): Emperical - Simple and Popular

Main MOS SPICE ParametersMain MOS SPICE Parameters

SPICE Parameters for ParasiticsSPICE Parameters for Parasitics

SPICE Transistors ParametersSPICE Transistors Parameters

Circuit Simulation Model of CMOS InverterCircuit Simulation Model of CMOS Inverter

Device Models PN Diode, MOSFET - University of...

Documents

Across From SHAKE SHACK - LoopNet · Shake Shack. Peter Levitan | Cell Phone:917.837.2916 | Email: peter@levitanrealestate.com. the LEVITAN wh patio Peo I e ou M Know X Inbox-peterlevitan@gm

Ameren Illinois Utilities - Levitan

Levitan Thomson 2007

MOSFET · MOSFET Da Wikipedia, l'enciclopedia libera. In elettronica, il MOSFET, abbreviazione del termine Due MOSFET di potenza inglese metal–oxide–semiconductor field-effect

MOSFET: Polarização do MOSFET Aula 4

Isaak Levitan, Lyrical landscape

Jan M. Rabaey Anantha Chandrakasan Borivoje Nikolicengrclasses.pitt.edu/electrical/faculty-staff/levitan/... · 2015. 8. 11. · EE141 1 © Digital Integrated Circuits2nd Arithmetic

Photo: Lois Levitan, RAPP New York State's Recycling Agricultural Plastics Project (RAPP): Lois Levitan,

The Levitan Pitch Presentation

Introduction to VLSI Design© Steven P. Levitan 1998 Introduction Introduction to VLSI Design l Instructor: Steven P. Levitan levitan@ee.pitt.edu l TA:

MD1822 High-Speed 4-Channel MOSFET Driver with Two Inverting … · 2018. 10. 25. · High-Speed, MOSFET Driver, MOSFET Driver, 4-Channel MOSFET Driver, MOSFET Driver with inverting

Isaac Levitan, peintre

Peter Levitan - How To Negotiate

“Nothing in biology makes sense except in the light of evolution.”levitan/BSC2011/Levitan bio2... · 2008. 3. 19. · Former French journalist Claude Vorilhon, who now calls himself

Mosfet Hochspannungsnetzteil - · PDF fileBauanleitungen / Netzteile Mosfet Hochspannungsnetzteil Kompaktes Mosfet Hochspannungsnetzteil bis 400V Hochspannungs-Netzteil für Röhrenverstärker

Updated MOSFET lecture material bhasler.ece.gatech.edu/Courses/ECE3400/Proj1/MOSFET_lecture_material.pdf · MOSFET Depletion Capacitors MOSFET Channel Capacitance MOSFET Overlap Capacitors

S.N. Jonkman B. Maaskant E. Boyd M. Levitan

Tableaux levitan 2

MOSFET & SPICE Models - Carnegie Mellon Universityece322/LECTURES/Lecture4/...1 18-322 Lecture 4 MOSFET & SPICE Models Outline • MOSFET Structure • MOSFET Operation • I-V Characteristic

Bonnie Alfriend, MIRM Charles Graham, MIRM Daniel Levitan, MIRM