Research On Radiation Damage Mechanism Of Bipolar Junction Transistor At Ultra-low Dose Rates

Due to the existence of various rays and high-energy particles in the space environment,the total ionization dose effect is one of the most serious threats faced by spacecraft that have been in orbit for a long time.As an important part of aerospace electronic systems,bipolar devices have the unique enhanced low dose rate sensitivity(ELDRS)effect.It is a critical issue that the international radiation resistance field and the aerospace field have been committed to conquering for a long time.The scope of mankind universe exploration has gradually expanded from near-earth space to the deep space environment along with the high-speed growth of space technology.Long-lived and highly reliable spacecraft have become a realistic demand for deep space exploration missions.At the same time,the deep space radiation environment with a low dose rate also brings more significant challenges to bipolar devices for aerospace.Early studies believe that when the radiation dose rate is lower than 10 mrad(Si)/s,the ELDRS effect of bipolar devices will reach saturation.However,in recent years,studies have found that the radiation damage enhancement factors of some bipolar devices continue to increase under the lower dose rates.This phenomenon questions the accuracy of the current evaluation standards because these standards usually use 10 mrad(Si)/s dose rate to determine whether the device has the ELDRS effect.In addition,the recent research at domestic and abroad for the ELDRS effect is mainly focused on the dose rate level of 10 mrad(Si)/s.Under the condition of the dose rate below 10 mrad(Si)/s,the unsaturation mechanism of the radiation damage enhancement factor of the bipolar device is still unclear.Therefore,it is imperative to study the physical mechanism of the radiation damage of bipolar devices at very low dose rates.Based on the space radiation environment where bipolar devices are applied and the existing problems in the current ELDRS effect research,combined with the existing theoretical models and defect theories,this paper selects the gate-controlled bipolar transistor with a special test structure as the main research object,and chooses ⁶⁰Co-?rays as the radiation source,the first research on the radiation damage mechanism of bipolar transistors with the irradiation dose rate of less than 10 mrad(Si)/s was conducted.(1)Carried out the total ionization dose irradiation experiment of the gate-controlled bipolar transistors at different extremely low dose rates,completed the quantitative separation of radiation-induced trap charges under the condition of dose rate lower than 10 mrad(Si)/s for the first time,and obtained the degradation law of the macroscopic electrical parameters and the change trend of the radiation-induced trap charges of the gate-controlled bipolar transistors under the extremely low dose rates,focused on the key defect types which cause the enhanced radiation damage of the bipolar transistors at ultra-low dose rates,and preliminary analysis of the key process of its defect evolution;(2)carried out the total ionization dose irradiation experiment of GLPNP bipolar transistors under different gate voltages,explored the influence of electric field on the evolution process of defects in the oxide layer,and analyzed the key process leading to the enhancement of the radiation damage of the bipolar transistors;(3)the total ionization dose irradiation experiment of GLPNP bipolar transistors at different temperatures was carried out,the influence of temperature on the evolution of defects in the oxide layer was studied,and the key process of radiation damage enhancement of bipolar transistors was summarized,which clarified radiation damage mechanism of bipolar transistors at ultra-low dose rates.The test results indicate that the radiation-induced interface trap charges and oxide trap charges are the key defects in the total ionization dose effect which cause radiation damage to bipolar transistors.The competitive process between hole trapping and electron recombination in the isolate oxide layer of bipolar transistors,leading to the difference in the release of protons in the layer is the key process that produces the ELDRS effect.