Study On Degradation Mechanism Of Silicon Carbide Power MOSFET Under Typical Stress

Due to the advantages of physical properties,silicon carbide(Si C)material is obviously superior to silicon material in high temperature,high power and high frequency applications,and silicon carbide power devices have become the most promising semiconductor devices to replace silicon(Si)based power devices.Therefore,the reliability of silicon carbide power metal-oxide-semiconductor field effect transistor(MOSFET)has attracted people’s attention.In this paper,the reliability evaluation and degradation mechanism of Si C power MOSFET before and after high temperature gate bias stress(HTGB),irradiation stress and surge current stress experiments have analyzed.The main research contents and results of this paper are as follows.:(1)The reliability of the devices at the maximum junction temperature of 150 ~oC was evaluated.By adjusting the gate voltage,the degradation law of the devices under different working conditions in high temperature environment was explored.The experimental results show that the threshold voltage of the devices has a significant change after high temperature gate bias experiment.The change of the threshold voltage is related to the gate voltage applied on the devices.The larger the gate voltage,the greater the change of the threshold voltage and on-resistance of the devices.At the maximum gate voltage,the threshold voltage changed by+54.9%and the on-resistance changed by+13.1%.This is because the electrons in semiconductor materials are converted into hot electrons at high temperature and high pressure,and injected into the gate oxide layer.(2)Through the total dose irradiation experiment and heavy ion irradiation experiment,the reliability problems of the devices in space application are simulated.In the total dose irradiation experiment,by applying positive bias,negative bias and zero bias gate voltage to simulate the devices in the open state,off state and static state.The experimental results show that the threshold voltage of the devices decreases and the saturation current increases after irradiation.Under positive bias voltage,the variation of electrical parameters is the largest,and the variation values of threshold voltage and saturation current are-33.12%and+100.87%,respectively.This is because the applied voltage is not conducive to the recombination of electron-hole pairs generated by high energy radiation.In heavy ion irradiation experiment,single particle burn-out results in devices failure and the threshold voltage drops to 0.073 V.The characterization of the devices after the experiment is carried out by means of electrical performance test,capacitance curve test,and micro-optic microscope.After the particles are incident on the devices,a large number of electron-hole pairs are deposited in the incident path,and a transient current is formed under the action of voltage.The avalanche effect is generated by the opening of the parasitic transistor inside the devices.The transient current increases and local overheating occurs,resulting in the failure of the devices due to thermal breakdown.(3)In the practical application of silicon carbide power MOSFET,the parasitic inductance and capacitance in the circuit will produce surge current in the circuit when the circuit is open.By adjusting the gate voltage,the degradation mechanism of the devices after repeated surge stress experiments under semi-open and shut-off states was explored.The degradation behavior of the devices is different after the experiment in the semi-open state and the shutdown state,and the on-resistance changes are+20.70%and-16.16%,respectively.The reason for the failure of the devices in the semi-open state is that the electron in the channel absorbs heat and inject into the gate oxide layer through thermal ionization emission.In turn-off state,the devices is equivalent to a negative bias high temperature gate bias stress.The hole is injected into the gate oxide layer through the voltage,resulting in the degradation of the devices.