Accuracy of Three Inter-Terminal Capacitance Models for SiC Power MOSFETs under Fast Switching
ABSTARCT :
This paper presents a comprehensive analysis of non-linear voltage-dependent capacitances of vertical SiC power MOSFETs with lateral channel, focusing specifically on fast switching transients. The capacitance-voltage (C-V) device characteristics, (Cgs, Cgd, Cds), being dependent on both Vgs and Vds, are extracted by means of two-dimensional Technology Computer Aided Design (TCAD) simulations for a commercially available device in both off- and on-state modes. Different compact models for the power MOSFET are investigated, each employing a three inter-terminal capacitance model as typically used in power electronics.The performed analysis provides a detailed explanation for the importance of taking into account the dependence of Cgd, Cgs and Cds on both of the voltages Vgs and Vds. This is especially important for fast switching transients (in the range of 10 ns) in order to accurately predict switching losses, driver losses, current and voltage slopes, as well as current and voltage delays. As direct measurements for Cgd, Cgs and Cds in dependence of both Vgs and Vds are highly demanding, the results presented in this paper increase the understanding of both the underlying effects as well as of the trade-offs between accuracy and computational complexity made by simplifying device models. In turn, this information is highly beneficial for enabling accurate and computationally efficient automated design procedures for power electronics.
EXISTING SYSTEM :
? In order to make the most out of Wide Band Gap materials in application, the packaging of the devices needs to be reconsidered.
? The conventional structure of existing Si and SiC power modules means that the current paths are formed by means of Aluminium (Al) bonding wires which connect the terminals of the package to the semiconductor die.
? This die is soldered to a direct copper bonding substrate (DCB) which in turn electrically isolates the die from the base of the package while still providing sufficient thermal transfer of heat.
? All of the components are then encapsulated with Silicone gel in order to provide protection against environmental effects, such as humidity and dirt.
DISADVANTAGE :
? The typical response to this problem has been the addition of a SiC Schottky Barrier Diode (SBD) which has a lower forward voltage and faster recovery time.
? Regardless of the cause, an uncontrolled short-circuit event can cause serious damage to a system as well as to sensitive loads.
? Thus it becomes necessary to protect the system against such events.
? SiC MOSFETs are especially susceptible to damage as a result of short-circuiting events due to their fast switching speeds and very low on-state resistance.
PROPOSED SYSTEM :
• The modeling of interface charge density is found to be necessary to describe the electrostatics of SiC power MOSFETs when operating at simultaneous high current and high voltage regions.
• The proposed compact model accurately fits the measurement data extracted of a 160 milli ohms, 1200V SiC power MOSFET in the complete IV plane from drain-voltage Vd = 5mV up to 800 V and current ranges from few mA to 30 A.
• To minimize the effect of self-heating in the measurements and to achieve high accuracy in the high voltage and high current IV characteristics of the DUT, we use the technique and considerations explained in.
ADVANTAGE :
? It was shown that non-linear voltage-dependence of interterminal MOSFET capacitances determine the dynamic performance of power MOSFETs.
? In contrast to compact device models, numerical simulation of semiconductor devices in TCAD tools provides a more accurate modelling of device physics, and a deeper insight into the device performance, which can neither be gained accurately by DPT nor by calorimetric measurements.
? The 2D TCAD model was calibrated to match the I-V and C-V device characteristics as close as possible, while observing the performance variation between several C2M0080120D devices.
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