cambridge university napoli university isie, dubrovnik, june 21st 2005 accurate physical model for...

ISIE, Dubrovnik, June 21st 2005CAMBRIDGEUNIVERSITY

NAPOLI

UNIVERSITY

Accurate Physical Model for the Lateral IGBT in Silicon On Insulator Technology

Ettore Napoli1,2, Vasantha Pathirana1, Florin Udrea1,3

1 Dept. of Engineering, University of Cambridge, UK2 Dept. Electronic and Telecom. Univ. of Napoli, Italy3 Cambridge Semiconductor (CamSemi), UK

EU research program ROBUSPIC


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Outline

Motivation Thin SOI LIGBT Differences with Vertical IGBT Spice sub-circuit model for LIGBT

Model equations Model behavior Numerical results Conclusion


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Motivation

• Available IGBT circuit models are not suited to Lateral IGBT

• Need for– a reliable physical based model for Lateral IGBT– usable in various circuit simulators

• Extension to different LIGBT technologies

• Important for smart power design


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Thin SOI Lateral IGBT

• 600V PT• Transparent buffer• Source and Drain up to the BOX• Current flow is horizontal and 1D


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Differences with Vertical IGBT (1)

• Not zero carrier concentration at the collector edge for LIGBT


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• Electrons injected from the n+ accumulation layer into the n- drift across the n+/n- junction.

• The structure features double injection (similar to a PIN or a thyristor)

N+

N+G DS

NN-

P+

P+


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• Total charge and charge profile

LIGBT

Vertical IGBT

LW

LxPLxWPxp W

sinh

sinhsinh0

LWqALPPQ W 2tanh0

LW

LxWPxp

sinh

sinh0

LWqALPQ 2tanh0



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• Depletion width vs. reverse voltage is influenced by 2D effects


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Differences with Vertical IGBT (5)• Depletion width LIGBT vs. Vertical IGBT• 0V

N+

G

G

D

D

S

S

NN-

P+

P+

NN-

P+

P+


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N+

G

G

D

D

S

S

NN-

P+

P+

NN-

P+

P+


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N+

G D

D

S

S

NN-

P+

P+

NN-

P+

P+


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• Depletion region mobile charge effect


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IGBT models not suited for LIGBT

• Voltage rise at turn-off is faster due to lower charge in the epilayer and slower depletion width expansion


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Spice sub-circuit model for LIGBT

Currents and voltages Epilayer charge equation


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Cox

Cgs

I (W)N

IPC_TRNI (0)NI (W)NI (W)P

Cdep

Cds

Q

Vdrift

Drain

Source

Gate

Vj

Vmos

N+

G DS

NN-

BOX

Substrate

P+

P+

I (0)N

VjVdriftVmos

I (W)N

I (W)P

• Vj : Emitter junction• Vdrift:Depends on the injected carriers

– analytic solution• Vmos: Mosfet (level 1)


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N+

G DS

NN-

BOX

Substrate

P+

P+

I (0)N

VjVdriftVmos

I (W)N

I (W)P

• IN(W) : Electron current through the level 1 Mosfet

Cox

Cgs

I (W)N


Cdep

Cds

Q

Vdrift

Drain

Source

Gate

Vj

Vmos


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Cox

Cgs

I (W)N


Cdep

Cds

Q

Vdrift

Drain

Source

Gate

Vj

Vmos

N+

G DS

NN-

BOX

Substrate

P+

P+

I (0)N

VjVdriftVmos

I (W)N

I (W)P

• IP(W) : Bipolar hole current

(W/L)b(W/L)P

(W/L)b

(W/L)P

L

qADI

bn

PWI

w

sne

i

P

sinh

1coth

sinh

1coth

)(0

2

20


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Cox

Cgs

I (W)N


Cdep

Cds

Q

Vdrift

Drain

Source

Gate

Vj

Vmos

N+

G DS

NN-

BOX

Substrate

P+

P+

I (0)N

VjVdriftVmos

I (W)N

I (W)P

• IN(0) : Electron current through the emitter junction

2

20

200)0(

i

sne

i

BsneN

n

PI

n

)P(NPII


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Cox

Cgs

I (W)N


Cdep

Cds

Q

Vdrift

Drain

Source

Gate

Vj

Vmos

• IPC_TRN : Transient current due to charge sweep-out

t

tWtWqApI TRNPC

_

Increasing Anode Voltage

Stable Anode Voltage

P

0

PW

Wt Wt+δt Wt+2δt

Time is increasing

0


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Base charge equation

IN(W) is the MOSFET current

IN(0) is the emitter edge electron current

IPC_TRN is the charge sweep out current

The last term is for the recombination in the base

Q

IIWIt

QTRNPCNN

_0


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Other model features

Carrier concentration dependent mobility model

Gate-Source Drain-Source and Gate-Drain capacitances are implemented

Physical based model with 17 parameters


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Name Meaning Unit

Vth Threshold voltage V

Nb Drift doping cm^-3

Wb Drift region length (51e-4) cm

Wnw N well length cm

Wfp Field plate extension cm

un Electron mobility cm^2/Vs

up Hole mobility cm^2/Vs

A Device transversal area cm^2

Kp Mos transconductance A/V^2

Name Meaning Unit

Isne P+ emitter inverse saturation current

A

Cbcj Body Drift region depletion capacitance factor

F/cm^2

Cox oxide Gate Drain capacitance F/cm^2

Cgs gate source capacitance F/cm^2

Taub drift region ambipolar lifetime (0.35e-6)

s

pw_ratio P(0)/P(W)

W_inc Depletion width expansion factor

V_fp Field plate depletion voltage V

Spice circuit parameters


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Proposed modelNumerical simulation

Ano

de c

urre

nt [A

]

Anode Voltage [V]0

0

Vg=5V

Vg=4V

Vg=3V

Vg=2V

1

1

2

2

3

3

4

4

5

5

Static characteristics


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Model behavior

Inductive Turn-off

Expanded for I=1A, V=200V

VoltageCurrentPower


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V=200V, I=2A. V=400V, I=2A.

Transient behavior


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U 5

L I G B T

0

1

2A

NO

G A TE KA

T

V 12 0 0

0

V d d

G

0

A

R 1

1 0

R 4

2 0 0

0

V g t r

TD = 5 1 0 n

TF = 1 0 nP W = 5 0 0 nP E R = 1 0 0 0 n

V 1 = 5

TR = 1 0 n

V 2 = 0

Resistive switch, 200 resistor load

Transient behavior


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Model behavior

• Toff Energy vs. Von as a function of lifetime


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Conclusion

• A physical based circuit model for Lateral IGBT• Implemented in Spice• Defined through 17 physical parameters• Compared against device numerical simulation• Extendable to Thick SOI and JI-LIGBT

cambridge university napoli university isie, dubrovnik, june 21st 2005 accurate physical model for...

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