Research On Key Test Technology Of Domestic GaN Devices

GaN devices are widely used in base stations of wireless communications,radar and aerospace systems due to their wide bandgap,high breakdown voltage,high electronic saturation speed,high thermal conductivity as well as strong radiation resistance.As a key component,the GaN power field-transistor seriously affects and limits the overall performance of the domestic solid-state power amplifiers for spacecraft.In recent years,the imported high-performance GaN power field-effect transistors are more widely used in solid-state power amplifiers.However,with the key microwave devices abroad are embargoed against China,the procurement of high–level GaN power devices is becoming more and more difficult.According to the analysis of projects to be launched and being demonstrated during the 13th Five-Year Plan period in China,there is a large demand and variety for space-borne solid-state devices.If all GaN devices to be used are imported from abroad,there will be problems such as high import cost and high military expenditure.Meanwhile,the development of our space satellites will be constrained by others.Therefore,independent research and development of high performance and high reliability GaN microwave devices is the only way for the future development of space-borne solid-state amplifiers.After years of technological innovation and improvement,domestic GaN devices have been gradually developed.However,whether domestic GaN devices can be reliably used in spacecraft systems requires a comprehensive reliability assessment.On the basis of studying the inherent characteristics,failure modes and failure mechanism of GaN devices,combining with the needs of aerospace applications,drawing lessons from the latest Aerospace evaluation technology,a technical scheme for reliability evaluation of GaN devices is proposed and verified by domestic samples in this paper.The main contents of this paper are as follows:1.The basic properties of GaN material and typical effects of GaN are studied,whichinclude low temperature effect,high temperature effect and voltage characteristics.2.Base on the inherent reliability weaknesses of GaN devices and the requirements of aerospace applications,a comprehensive reliability evaluation scheme for GaN devices is developed.Overall,the evaluation scheme includes five parts:fuctional performance analysis(compared with imported devices),structural analysis,limit assessment,accelerated life test and passive component application verification,and can be recognized as a set of pioneering reliability evaluation technology and methods for GaN devices.3.GaN HEMT devices with 0.35um PT process are selected for the test.The test samples include GaN power transistor chip,capacitance(MIM capacitance)and resistance two categories:one is the 16mm chip,the other is the PCM test chip of various small sizes.The conclusion of the evaluation tests are as follows:the performance evaluation results show that the high and low temperature meets the expected requirements.The structure analysis checks the structure and material of the device and there is no abnormality;the limit condition evaluation test finds that the device performance well during test and still has large margin compared with normal use condition.The life tests contain DC and RF life test.The test result show that the MTTF of the device is over 10~5 hours when the channel temperature is 225?(maximum operating temperature),and the device has a good performance without abnormality after 1000 hours continuous operation under RF condition and 4000 switching times.Passive component evaluation is used to check the quality of chip bonding and soldering,and the test results meet the requirements.