Device Temperature and Heat Generation in Power Metal-Oxide Semiconductor Field Effect Transistors

Abstract

A numerical thermal-electrical model has been established for a typical power metal-oxide semiconductor field effect transistor (MOSFET) device in this work. The temperature and heat-generation distributions within the device are obtained and their effects on the device I- V characteristics are examined. Drain currents in both the cutoff state and the on-state increase with an increase of ambient temperatures in the entire range of v ds from the ohmic region to the breakdown region. The thermal impact on the I d - V ds curves in the cutoff state and the on-state is displayed in terms of different prebreakdown behaviors. An abrupt temperature rise occurring before the traditionally known onset of the avalanche breakdown of the drain-body p-n junction is observed in this work. Unlike the well-recognized avalanche breakdown mechanism, the microscopic mechanism for this temperature rise is not yet clearly understood. It is observed that, although the highest temperature does not occur in the channel region, the temperature gradient along the channel is the highest in the device domain. It is shown that the maximum heat generation occurs in the channel region. The magnitude of the heat generation in the channel region is found to be two orders higher than that in the drift region. This high local heat generation must be considered in the optimal design of power MOSFET devices to reduce the temperature, and more importantly, the temperature variation in the channel region for a more reliable performance of MOSFET in high-temperature applications.