Research Of Thermal Safe Operating Area Of Split-Gate Power MOSFET Devices

Split-Gate Power Metal-Oxide-Semiconductor Field-Effect Transistors(SGT Power MOSFETs)are used widely in automotive electronics,communications and other fields.Support for hot-swap technology is an important requirement for SGT power MOSFET devices when used.Hot swapping requires power devices to operate under high voltage and high current conditions for longer periods of time(milliseconds)and requires devices with a wider Thermal Safe Operating Area(T-SOA).Failure of the exceeding thermal SOA mechanism of SGT power MOSFET devices is investigated and previous thermal SOA models are reconstructed and improved.The SGT power MOSFET are firstly described in detail in terms of operating principle,electrical and thermal characteristics.Then,the device exceeds the thermal SOA failure mechanism is studied and analyzed.The study shows that the main reason for the device’s exceeding thermal SOA failure is that the previous thermal SOA model does not take into account the current variation caused by the positive thermal coefficient of the device drain current when calculating the maximum power limit line.Next,the relationship between the current thermal coefficient(d Id/d T)and the main structural parameters of the device is obtained by T-CAD software and mathematical methods.The larger the width to length ratio of the device channel and the larger the Pbody doping concentration,the larger the current thermal coefficient and the smaller the thermal SOA area;the thermal SOA area increases and then decreases with the increase of the gate oxide thickness.Finally,based on the 100 V commercial device,the current thermal coefficient is integrated from the initial temperature to the maximum junction temperature range when calculating the device’s maximum power limit line,so as to complete the correction of the drain current model,based on which a test platform is built to test the thermal SOA of the device and verify the accuracy of the model.Compared with the results of the traditional thermal SOA model and the improved thermal SOA model,the average relative error between the maximum power limit line calculated by the traditional thermal SOA theoretical model and the measured results is more than a factor of one,while the average relative error between the maximum power limit line calculated by the improved thermal SOA model and the measured results is only 9.7%,which significantly improves the accuracy of the model and provides a good basis for the accurate evaluation of the thermal SOA of SGT power MOSFET devices.