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ISPSD, Santa Barbara, May 2005CAMBRIDGEUNIVERSITY
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UNIVERSITY
A compact model for thin SOI LIGBTs:description, experimental verification
and system application
Ettore Napoli1,2, Vasantha Pathirana1, Florin Udrea1,3,Guillaumme Bonnet3,Tanja Trajkovic3,Gehan Amaratunga3
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
Half bridge circuit using lateral IGBT Experimental results on flyback circuit 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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IGBT models not suited for LIGBT (1)
• 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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Differences with Vertical IGBT (2)
• Depletion width vs. reverse voltage is influenced by 2D effects
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IGBT models not suited for LIGBT (2)
• Voltage rise at turn-off is faster due to lower charge in the epilayer and slower depletion width expansion
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IGBT models not suited for LIGBT (3)
• Important effects such as the voltage bump, resulting in a delay in the turn-off, are not considered
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Spice sub-circuit model for LIGBT
Currents and voltages Epilayer charge equation
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Spice sub-circuit model for LIGBT
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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Spice sub-circuit model for LIGBT
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
• IN(W) : Electron current through the level 1 Mosfet
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ISPSD, Santa Barbara, May 2005CAMBRIDGEUNIVERSITY
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Spice sub-circuit model for LIGBT
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
• 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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ISPSD, Santa Barbara, May 2005CAMBRIDGEUNIVERSITY
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UNIVERSITY
Spice sub-circuit model for LIGBT
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
• 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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ISPSD, Santa Barbara, May 2005CAMBRIDGEUNIVERSITY
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UNIVERSITY
Spice sub-circuit model for LIGBT
Cox
Cgs
I (W)N
IPC_TRNI (0)NI (W)NI (W)P
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 13 parameters
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Model behavior
Inductive Turn-off
Expanded for I=1A, V=200V
VoltageCurrentPower
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Model behavior
• Toff Energy vs. Von as a function of lifetime
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Half bridge circuit
• Output characteristics
200V; 2A; 100kHz
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Experimental results on flyback circuit
E xpe rim en ta l re su lts V g = 5V
V g = 4V
V g = 3V
V g = 2V
D ra in v o lta g e [V ]0
0 .5Dra
in c
urre
nt [
A]
1 4 5
O u r m o de l
0
1 .5
1
2
2 3
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ISPSD, Santa Barbara, May 2005CAMBRIDGEUNIVERSITY
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Experimental results on flyback circuit
Dra
in V
olta
ge [
V]
Dra
in C
urre
nt [
A]
Pow
er [
kW]
0
0
0 .2
0 .2
0 .4
0 .1
0 .6
0 .3
0 .8
1 .0
1 .2
Tim e [n s]5 0 1 0 00 2 0 0 2 5 01 5 0 3 0 0
0
8 0
1 6 0
2 4 0
3 2 0
4 0 0
4 8 0
E x p e rim e n ta l re s u ltO u r m o d e l
E x p e rim e n ta l re s u ltO u r m o d e l
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Flyback circuit simulation1K
20
47pF
D22 F
1mF
100V
LIGBT
Complete flyback circuit
The simulated waveforms are for the primary winding voltage (green) and the load voltage (red)
Time [ s]
Vol
tage
[V
]
0 20 40 60 80 100
0
100
200
-100
-200
-300
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ISPSD, Santa Barbara, May 2005CAMBRIDGEUNIVERSITY
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Conclusion
• A physical based circuit model for Lateral IGBT• Implemented in Spice• Compared against
– Device numerical simulation– Complex SMPS simulation– Experimental results
• Extendable to Thick SOI and JI-LIGBT