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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, UK 2 Dept. Electronic and Telecom. Univ. of Napoli, Italy 3 Cambridge Semiconductor (CamSemi), UK EU research program ROBUSPIC CAMBRIDGE UNIVERSITY NAPOLI UNIVERSITY ISPSD, Santa Barbara, May 2005 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 CAMBRIDGE UNIVERSITY NAPOLI UNIVERSITY ISPSD, Santa Barbara, May 2005 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 CAMBRIDGE UNIVERSITY NAPOLI UNIVERSITY ISPSD, Santa Barbara, May 2005 Thin SOI Lateral IGBT • • • • 600V PT Transparent buffer Source and Drain up to the BOX Current flow is horizontal and 1D CAMBRIDGE UNIVERSITY NAPOLI UNIVERSITY ISPSD, Santa Barbara, May 2005 Differences with Vertical IGBT (1) • Not zero carrier concentration at the collector edge for LIGBT CAMBRIDGE UNIVERSITY NAPOLI UNIVERSITY ISPSD, Santa Barbara, May 2005 IGBT models not suited for LIGBT (1) • Total charge and charge profile LIGBT Q P0 PW qAL tanh W 2L P0 sinh W x L PW sinh x L p x sinh W L Vertical IGBT Q P0 qAL tanh W 2L sinh W x L p x P0 sinh W L CAMBRIDGE UNIVERSITY NAPOLI UNIVERSITY ISPSD, Santa Barbara, May 2005 Differences with Vertical IGBT (2) • Depletion width vs. reverse voltage is influenced by 2D effects CAMBRIDGE UNIVERSITY NAPOLI UNIVERSITY ISPSD, Santa Barbara, May 2005 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 CAMBRIDGE UNIVERSITY NAPOLI UNIVERSITY ISPSD, Santa Barbara, May 2005 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 CAMBRIDGE UNIVERSITY NAPOLI UNIVERSITY ISPSD, Santa Barbara, May 2005 Spice sub-circuit model for LIGBT Currents and voltages CAMBRIDGE UNIVERSITY NAPOLI UNIVERSITY Epilayer charge equation ISPSD, Santa Barbara, May 2005 Spice sub-circuit model for LIGBT Drain S Vj Vdrift Cox Cdep N Gate Vmos IP(W) Q Cds + IN(0) IN(W) IPC_TRN BOX IN(W) Cgs G + P Vmos IN(W) IP(W) N - Vdrift IN(0) D N P + Vj Substrate Source • Vj : Emitter junction • Vdrift: Depends on the injected carriers – analytic solution • Vmos: Mosfet (level 1) CAMBRIDGE UNIVERSITY NAPOLI UNIVERSITY ISPSD, Santa Barbara, May 2005 Spice sub-circuit model for LIGBT Drain S Vj Vdrift Cox Cdep N Gate Vmos IP(W) Q Cds + IN(0) IN(W) IPC_TRN BOX IN(W) Cgs G + P Vmos IN(W) IP(W) N - IN(0) D N P Vdrift + Vj Substrate Source • IN(W) : Electron current through the level 1 Mosfet CAMBRIDGE UNIVERSITY NAPOLI UNIVERSITY ISPSD, Santa Barbara, May 2005 Spice sub-circuit model for LIGBT Drain S Vj Vdrift Cox Cdep N Gate Vmos IP(W) Q Cds + IN(0) IN(W) IPC_TRN BOX IN(W) Cgs G + P Vmos IN(W) IP(W) N - Vdrift IN(0) D N P + Vj Substrate Source • IP(W) : Bipolar hole current coth (W/L) 1 P0 2 b sinh (W/L) P qAD I P (W ) 0 2 I sne L bni 1 Pw coth (W/L) b sinh (W/L) CAMBRIDGE UNIVERSITY NAPOLI UNIVERSITY ISPSD, Santa Barbara, May 2005 Spice sub-circuit model for LIGBT Drain S Vj Vdrift Cox Cdep N Gate Vmos IP(W) Q Cds + + P IN(0) IN(W) IPC_TRN BOX IN(W) Cgs G IN(W) IP(W) Vmos N - Vdrift IN(0) D N P + Vj Substrate Source • IN(0) : Electron current through the emitter junction I N (0) I sne CAMBRIDGE UNIVERSITY P0(N B P0 ) ni 2 NAPOLI UNIVERSITY I sne P0 2 ni 2 ISPSD, Santa Barbara, May 2005 Spice sub-circuit model for LIGBT Drain P Vj Time is increasing Vdrift Cox Cdep Gate Vmos IP(W) Q Cds PW IN(0) IN(W) IPC_TRN Wt IN(W) Cgs Source • IPC_TRN : 0 Wt+δt Wt+2δ Increasing Anodet Voltage 0 Stable Anode Voltage Transient current due to charge sweep-out I PC _ TRN CAMBRIDGE UNIVERSITY W t qApW t t NAPOLI UNIVERSITY ISPSD, Santa Barbara, May 2005 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 Q I N W I N 0 I PC _ TRN t CAMBRIDGE UNIVERSITY NAPOLI UNIVERSITY ISPSD, Santa Barbara, May 2005 Other model features Carrier concentration dependent mobility model Gate-Source Drain-Source and Gate-Drain capacitances are implemented Physical based model with 13 parameters CAMBRIDGE UNIVERSITY NAPOLI UNIVERSITY ISPSD, Santa Barbara, May 2005 Model behavior Expanded for I=1A, V=200V Voltage Current Power Inductive Turn-off CAMBRIDGE UNIVERSITY NAPOLI UNIVERSITY ISPSD, Santa Barbara, May 2005 Model behavior • Toff Energy vs. Von as a function of lifetime CAMBRIDGE UNIVERSITY NAPOLI UNIVERSITY ISPSD, Santa Barbara, May 2005 Half bridge circuit • Output characteristics 200V; 2A; 100kHz CAMBRIDGE UNIVERSITY NAPOLI UNIVERSITY ISPSD, Santa Barbara, May 2005 Experimental results on flyback circuit 2 Drain current [A] Experimental results Our model 1.5 Vg=4V 1 0.5 0 CAMBRIDGE UNIVERSITY Vg=5V Vg=3V Vg=2V 0 1 2 3 Drain voltage [V] NAPOLI UNIVERSITY 4 5 ISPSD, Santa Barbara, May 2005 Experimental results on flyback circuit Power [kW] 1.0 480 Experimental result Our model 400 0.8 320 0.6 240 0.4 160 0.2 80 0 0.3 0 Drain Voltage [V] Drain Current [A] 1.2 Experimental result Our model 0.2 0.1 0 0 CAMBRIDGE UNIVERSITY 50 100 150 Time [ns] NAPOLI UNIVERSITY 200 250 300 ISPSD, Santa Barbara, May 2005 Flyback circuit simulation 1K 1mF 20 Complete flyback circuit 47pF 22F 100V D LIGBT The simulated waveforms are for the primary winding voltage (green) and the load voltage (red) 200 Voltage [V] 100 0 -100 -200 -300 0 20 40 CAMBRIDGE UNIVERSITY 60 Time [s] 80 100 NAPOLI UNIVERSITY ISPSD, Santa Barbara, May 2005 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 CAMBRIDGE UNIVERSITY NAPOLI UNIVERSITY ISPSD, Santa Barbara, May 2005
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