Online proceedings - EDA Publishing Association

7-9 October 2009, Leuven, Belgium
IV.
CONCLUSION
Fig.10. Commutation simulation (dotted) vs. measurement across MOSFET
at 150°C
Although the two figures look identical there is a subtle
difference between them, this difference is illustrated on
“Fig.11.” a Comparison between measurement at 25°C and
150°C are shown, using the drain to source voltage at the end
of the MOSFET commutation.
In this paper, an electrical model using VHDL-AMS code of a
power vertical MOSFET sensitive to temperature has been
shown. The modeling approach and the thermal sensitivity of
MOSFET parameters have been discussed. This model is
simple one, the equation used to model the electrical and the
thermal issues are easy to code with any simulator, the non
linear capacitor equation used is more accurate and rapid than
the conventional one used with other models. Finally this
model will be used as a unit for a distributed electro-thermal
simulation, and each unit will give us the image of the local
temperature of the modeled device, which will give us an idea
for the current distribution in the ship and hotspots. Validation
of the model accuracy has been shown. So this work is the first
step to electro-thermal simulation of power device by simulator
coupling.
Fig.11. Drain to source voltage measurement across MOSFET at 25°C and
150°C (dotted)(zoom on oscillations)
The only significant difference between simulation and
measurement is on the final phase “Fig.12.” it’s clear that the
measurement oscillations are more rapidly damped, this is due
to the skin effect.
REFERENCES
[1] JB.Sauveplane et al., “Smart 3-D Finite-Element Modeling for the
Design of Ultra-Low On-Resistance MOSFET”, IEEE Transactions
on Advanced Packaging, Nov. 2007, V30-4,pp 789-794.
[2] JB.Sauveplane et al., “3D electro-thermal investigations for
reliability of ultra low ON state resistance power MOSFET”,
Microelectronics Reliability, V48 - 8-9, Sep. 2008, pp 1464-1467
[3] S.Wünche, “Simulator Coupling for Electro-Thermal Simulation Of
Integrated Circuits”, Therminic’96, 1996, pp 89-93.
[4] F.Morancho, “Modling and performance of vertical trench
MOSFET in power electronics”, Semiconductor Conference, 1995.
CAS'95 Proceedings.
[5] C.Batard ;T.MEYNARD ;H.FOCH ;J.L.MASSOL
“Circuit oriented simulation of power semiconductor using
success.Application, to diodes and bipolar transistors”. EPE’91,
Florence.
[6] David Divins, “Using Simulation to Estimate MOSFET Junction
Temperature in a Circuit Application”. International Rectifier,
October 2007.
Fig.12. Drain to source voltage across MOSFET at 150°C (zoom on
oscillations)
The skin effect causes the effective resistance of the conductor
to increase with the frequency of the current. We used between
35 to 40 cm of a copper conductor cable for the connections
between the circuit elements, that’s mean there is enough cable
length in our circuit that the effective resistance change in the
cables affect the hall circuit performance. The oscillations
frequency is high (more than 1 MHz), so it’s normal that the
resistor increase, and the measured oscillations are damped
than the simulation due to this effective resistor, which had not
been taken into consideration in the simulation circuit .
©EDA Publishing/THERMINIC 2009 90
ISBN: 978-2-35500-010-2