Research On Temperature Reliability Of Cascode Structure GaN-based HEMT Device Dependent On Power Cycle

In recent years,GaN material devices have been more and more widely used in the fields of power electronics and communication electronics,playing an important role in the fields of voltage conversion,fast charging,and high-frequency communications.In this thesis,both experiments and simulation work on the reliability of power cycling temperature has been carried out on the Cascode structure GaN-based HEMT device.First of all,this work conducts extensive investigation and analysis on the parametric reliability and packaging reliability of GaN-based HEMT devices.It is determined that the main factors affecting the reliability of the internal parameters of GaN-based HEMT devices include the trap effect of the passivation layer,the barrier layer,the buffer layer and the metal contact layer,the inverse piezoelectric effect,and the hot electron effect.The reliability of the package level is embodied in the device bonding wire,solder layer,plastic package and so on.This thesis proposes to test the device parameters and the reliability of the package level through power cycling experiments.Secondly,this work studies the junction temperature test of Cascode structure gallium nitride HEMT devices.Aiming at the two parts of the die heat source inside the device,through comparison and analysis,the use of composite temperature-sensitive electrical parameters is proposed to eliminate the influence of the on-resistance of the gallium nitride tube connected in series with the silicon MOSFET,so as to quickly and accurately measure the device junction temperature.After the comparison of different test methods,the junction temperature test error of the test method proposed in this work is kept within 5%,which meets the requirements of the power cycle experiment.Subsequently,this work discusses two load heating circuits,the switching power consumption load and the conduction power consumption load.Through analysis and comparison,it is found that the two load circuits can realize the corresponding heating function,and each has its advantages and disadvantages.The switch load circuit can ensure that the load power of each device is a constant value,and the conduction load circuit has a simpler structure than the switch load circuit,and has lower power requirements.In addition,due to the introduction of more inductive components in the switching load circuit,the switching response capability of the entire power loop is severely reduced,and the load power is more likely to reach the saturation value.After comprehensive consideration of various influencing factors,this article finally chooses the conduction load circuit as the load heating circuit for the power cycle test.Next,this work carried out the power cycle aging test of the two groups of different junction temperature difference values of 100? and 150? on the experimental samples.By comparing the on-resistance,threshold voltage,off-state leakage current,and gate leakage current of the samples before and after the experiment,the on-resistance is taken as the main analysis object,and the devices with a higher degree of degradation after the aging experiment are selected for the unblocking experiment.The COMSOL thermodynamic simulation software is used to simulate the internal heat distribution of the device caused by the power cycle process,and it is obtained that the stress distribution at the solder joints at both ends of the device's bonding wire and the wire neck of the bonding point is the highest;There is obvious stress enhancement distribution at the edges and cuspidal point of the entire package.And there are fracture gaps at both ends of the silver glue layer of the fixed chip.Combining the microscopic observation results of unblocking and the results of thermodynamic simulation,the failure phenomenon is explained accordingly.Finally,this work analyzes the changes of the internal parameters of the device under the condition of power cycle temperature change through TCAD software.The effects of different trap distribution forms in the same part of the device and the concentration of trap distribution in different parts on the on-resistance,transconductance,saturation current,off-state leakage level and other parameters of the device under different temperature stress conditions are respectively discussed.The reason and physical mechanism of parameter degradation are explained.