Research On Improving Thermal Instability Of GaN HEMT

Gallium nitride(GaN)-based high electron mobility transistor(HEMT),with its high frequency,high power and high efficiency characteristics,has become an important power amplifier in the millimeter wave band of radar,fifth-generation mobile communications(5G)and other fields.However,due to the reliability of the device,the development of GaN HEMT devices still faces many challenges.Among these reliability problems,thermal instability caused by self-heating effect and thermal coupling effect is a major aspect in reliability research.This article focuses on the thermal reliability of gallium nitride(GaN)-based high electron mobility transistor(HEMTs)devices.In this paper,the thermal resistance of each part of the device is systematically studied based on finite element thermal simulation.By extracting data from the overall thermal distribution of the device,the relationship between the temperature of each point on the vertical line of the geometric center of the device and the distance in the vertical direction are obtained,thereby quantifying the thermal resistance of the different material layers of the device;and optimize the thermal resistance of the device from the perspective of the package form,the types of materials and the structure of each part;then by modeling the heat dissipation method of the device,the relationship expression between the device junction temperature and the thermal resistance of each part is obtained;by bringing the quantified thermal resistance of each part of the device into the expression,the judgment value of the thermal resistance of each part on the junction temperature is calculated,so as to provide some guidance for the optimization method of devices with different structures.For the multi-finger gate structure of GaN HEMT devices,this paper designs a computer program that can quickly calculate the spacing of multi-finger arrangements for the problem of thermal coupling between multiple fingers.It has been verified by finite element simulation that the maximum temperature difference on the heating finger is reduced by about 70%,indicating that the multi-finger arrangement scheme obtained through this procedure can effectively reduce the thermal coupling effect between multiple fingers.By inputting the basic parameters of layout design,the program can quickly obtain a multi-finger layout scheme,which is highly efficient and highly compatible,which greatly helps the design of the layout structure of the device.The program takes the two-finger thermal coupling relationship as a theoretical basis,and then obtains the functional relationship between the thermal coupling strength and the finger spacing through finite element simulation.The algorithm and code written in this way can directly calculate the temperature of each finger at different finger distances from known related parameters.Substitute the temperature on each finger to replace the overall temperature distribution of the device,thereby improving optimization efficiency.And through the exhaustive method,the optimal multi-finger spacing arrangement scheme with a certain accuracy is obtained.Finally,electrical and thermal tests were performed on the optimized device after tape-out,and the test data also verified the effect of optimization on the device junction temperature reduction.