High accurate SPICE model for medium to high voltage MOSFET (400V-900V)

Structure and features

As shown in Fig. 1, Toshiba’s DTMOS series applies Superjunction (SJ) structure in which P and N layers are alternately arranged in the drift layer. The high accurate SPICE model (G2 model) for SJ structure MOSFET (SJ-MOSFET) developed by Toshiba can express the saturation characteristics in the high current region of Drain current vs Drain-source Voltage (ID-VDS) charactaristics. And the abrupt capacitance change depending on the MOSFET Drain voltage shown in Fig. 2 is also reproduced by using the arbitrary function.

Fig. 1: Cross section of DTMOS SJ structure (outline drawing)
Fig. 1: Cross section of DTMOS SJ structure (outline drawing)
Fig. 2: Schematic of DTMOS SPICE model (outline drawing)
Fig. 2: Schematic of DTMOS SPICE model (outline drawing)

MOSFET fitting accuracy

Fig. 3 shows the reproduction level (called "fitting accuracy") by comparing the actual measurement of ID-VGS characteristics and ID-VDS characteristics of our SJ-MOSFET product TK040N65Z with the simulation using our SPICE model. In the High voltage breakdown MOSFET such as SJ-MOSFET,  Drain Current (ID) saturate due to the resistance effected by the deep and long drift layer. In our SPICE model, this saturation characteristic is expressed by a non-linear resister (RX) which applied to the drain side so the simulation curve can show actual measurement with accuracy even in the high current region.

Fig. 3: Comparison of the actual measurement and simulation of the G2 model (ID-VGS and ID-VDS)
Fig. 3: Comparison of the actual measurement and simulation of the G2 model (ID-VGS and ID-VDS)

Fig. 4 shows a comparison between actual measurement and simulation of the VDS dependencies on the Input capacitance (Ciss), the Output capacitance (Coss), and the Reverse transfer capacitance (Crss). The capacitance characteristics of SJ-MOSFET change rapidly with the depletion layer extending from the PN-junction due to the SJ structure. On the other hand, Toshiba's SPICE model can show the non-linearity of the measurement values with high accuracy by additional arbitrary functions of non-linear capacitance combination of Gate-souece (Cgs), Gate-drain (Cgd) and Drain-source (Cds).

Fig. 4: Comparison of the actual measurement and simulation of the G2 model (Capacitance characteristics)
Fig. 4: Comparison of the actual measurement and simulation of the G2 model (Capacitance characteristics)

Transient characteristics (inductance load switching operation) fitting accuracy

Fig. 5 shows a inductive load switching circuit diagram using SJ-MOSFET product TK040N65Z. And Fig. 6 shows the comparison between the actual waveform and the simulation using the G2 model for SJ-MOSFET as described above. By using our G2 model which can express the non-linearity of the capacitance characteristic with high accuracy, we can see very accurate waveforms that the rising of VDS and oscillation of VDS and ID, associated with oscillation of dVDS/dt or VGS. Our G2 model for SJ-MOSFET is a SPICE model that can sufficiently verify dynamic properties such as switching operation.

Figure 5: Inductance load switching circuit
Figure 5: Inductance load switching circuit
(a)VGS
(b)VDS
(c)ID

Fig. 6: Comparison of actual measurement and simulation of turn-off waveforms in inductance load switching circuit
(a)VGS (b)VDS (c)ID

Our high accurate SPICE model (G2 model) can reproduce the actual switching waveforms with high accuracy. The circuit verification by using high-accuracy simulation in advance of the actual production may reduce the double work for the circuit modification and help the development time shorten. Toshiba's high accurate SPICE model (G2 model) supports your circuit development and analysis effectively.

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