Research On Failure Mechanism And Life Prediction Methods For Vertical Double-diffused Power MOSFETs

Power MOSFET is one of the most frequently used power semiconductor devices in power electronics field.And VDMOSFET(Vertical Double-Diffused MOSFET)is extentively used in small and medium power application.But power MOSFET is also one of the highest failure rate devices in circuits and systems,its reliability plays an important part in the reliability of entire system.So the researches on reliability and life prediction methods of power MOSFET are of great significance.Because power MOSFET is long life and high reliability device,it is hard to attain the life data of it.So the characteristic parameters can be used to assess the reliability and predict the remaining useful life.Through accelerated degradation test(ADT),the parameters can be measured regularly.In this paper,according to the analysis of VDMOSFET's failure mechanisms,power MOSFET accelerated degradation test and parameters measurement system is designed.By this system and ADT scheme,lots of degradation data are acquired and will be used to build parameters' model and predict device's life.Firstly,main failure mechanisms of power MOSFET are researched and analysed,especially HEF and PBTI.Considering the effect on device's physical structure and parameters caused by HEF and PBTI,the characteristic parameters are selected,combined TCAD semiconductor simulation and ADT data.Then,power MOSFET accelerated degradation test and parameters measurement system is designed.The system can be used to do ADT for a batch of power MOSFETs and measure the charact eristic parameters automatically and regularly.The test data will be retured back to upper computer and analysed.Based on this system,ADT schemes of different voltage and temperature levels are designed and compeleted,in order to collect the degradatio n data.Eventually,based on the test data and existed classical stress model,the parameters' degradation models of HEF and PBTI effect are calculated respectively.According to the degradation models,the life of devices are predicted.Besides,Time Sequence Analysis(TSA)and Particle Filter Algorithm(PF)are also used to predict the devices' life.The life prediction results of these three methods are compared to determine the characters and applicable situations of each method.