Study of the Thermoelectric Properties of Powerful MOSFETs

MOSFETs are characterized by their ability to commutate high currents (tens to hundreds of amperes) at high frequency. At the same time, the dissipated power reaches 1 kW. Due to this it is required to assure effective heat dissipation from the active area of the crystal and develop appropriate means of controlling the junction–case thermal resistance. In this study, the results of studies of the thermoelectric properties of powerful MOSFETs are presented. The studies are carried out using a hardware-software complex, in which, together with the standard methods for measuring the junction–case thermal resistance, a modulation method is implemented that uses the heating of an object by heating current pulses with the harmonic pulse-width modulation law. To measure the temperature of the active area in the pauses between the heating pulses, the temperature-sensitive, or thermometric, parameter is measured, which is the source–drain voltage. To eliminate the impact of transient electrical processes on the results of thermal resistance measurements, the temperature-sensitive parameter values are extrapolated to the end of each heating pulse. For extrapolation, the root and logarithmic laws of the change in the temperature-sensitive parameter in the process of cooling the transistor crystal after its pulsed heating are used. It is demonstrated that the results of the measurements of the thermal resistance components obtained by various methods are in close agreement with each other.