Study On ELDRS Effect Acceleration Evaluation Method At Ultra-Low Dose Rate

Total Ionizing Dose(TID)is an important issue in the study of radiation effects in aerospace electronics systems.Bipolar devices,due to their unique Enhance Low Dose Rate Sensitivity(ELDRS)effect,have become a key research direction in the field of international radiation hardness in recent years.So far,the research on the ELDRS effect of bipolar devices has been mainly carried out at the dose rate level of 10 mrad(Si)/s,and early studies believe that the Low Dose Rate Enhance Factor(LDREF)will reach saturation at a lower dose rate(<10 mrad(Si)/s).However,recent studies have reported that in an ultra-low dose rate environment(<10 mrad(Si)/s),some bipolar devices show that LDREF continues to increase as the dose rate decreases,and there is no saturation trend.Considering that new applications such as long life satellites in high orbit and deep space exploration have caused spacecraft to face long-time low-dose rate radiation environment,whether the existing assessment method based on the dose rate of 10mrad(Si)/s can truly reflect the radiation damage characteristic at ultra-low space environment is still an worthy of attention issue.At present,research on accelerated evaluation methods for ELDRS effects at ultra-low dose rates(<10 mrad(Si)/s)has not been carried out,and the existing accelerated test methods cannot give a conservative evaluation result,resulting in the existing design margin for radiation resistance cannot meet the application requirements of some bipolar devices in ultra-low dose rate(<10mrad(Si)/s)radiation environment.Therefore,it is important to carry out research on radiation damage mechanism and accelerated test methods under ultra-low dose rate conditions to solve the verification and evaluation of the anti-total dose effect of bipolar devices.Based on the previous research on the radiation damage mechanism of ELDRS at the dose rate level of 10 mrad(Si)/s and the temperature-switched accelerated evaluation method,this thesis takes transistors and integrated circuits as the research object,and analyzes the performance of bipolar devices at ultra-low dose rate.The ELDRS is further studied,and an accelerated evaluation test method suitable for ultra-low dose rates will be established.In terms of rule of radiation effects,the test results show that bipolar devices have obvious dose rate effects at 10?1 mrad(Si)/s,and The radiation damage is still increasing at low dose rates(10 mrad(Si)/s).The LDREF of the bipolar device shows that the LDREF increases with the decrease of the dose rate,and without saturation trend.The results of this study further verify some bipolar devices exist the ultra-low dose rate damage enhancement effect,and provide an experimental reference for the establishment of the further step of the accelerated evaluation method.In terms of damage mechanism,through the irradiation test of gated lateral bipolar transistors with different gate voltages and different temperatures,the influence mechanism of electric field distribution and temperature on the TID of bipolar devices is analyzed,and the interface trap charge(Nit)under different temperature irradiation conditions is obtained.Interface trap charge growth-annealing competition mechanism is the direct cause of the diversity of the ELDRS effect of the device.The specific manifestations are as follows:(1)The interface trap charge density is negatively correlated with the gate voltage under the state of electron accumulation on the interface of Si-Si O2in the base area.The interface trap charge density decreases with the increase of the gate voltage,and the annealing mechanism of the interface trap charge is dominant;(2)The interface trap charge density and the gate voltage is proportional under the state of depletion of electrons on the interface of Si-Si O₂ in the base area.The higher the gate voltage,the greater the interface trap charge density,and the growth mechanism of the interface trap charge is dominant.The results of this study provide a theoretical basis for the establishment of accelerated evaluation methods at ultra-low dose rates.In terms of accelerated evaluation of ultra-low dose rate,based on the results of radiation damage to bipolar devices at different temperatures,dose rates,and doses,the key physical processes and key physical processes of the accelerated evaluation method for Temperature-Switched Irradiation(TSI)at extremely low dose rates have been established.The main mechanism of the test procedure is:(1)In the low-dose stage,increase the temperature to increase the hole escape rate,promote the release of proton H+,and promote the growth rate of the interface trap charge;(2)In the high-dose stage,appropriately reduce the temperature to inhibit the consumption of proton H⁺,and promote Interface traps grow.TSI accelerated evaluation results show that this method can conservatively evaluate the ELDRS effect of bipolar devices at ultra-low dose rates(<10 mrad(Si)/s),and the evaluation time can be shortened from about 12 months to 17hours.In summary,this article systematically studied the ELDRS effect of bipolar devices at very low dose rates(<10 mrad(Si)/s),and initially explored the effects of bipolar devices at very low doses(<10 mrad(Si)/s)radiation damage mechanism,and use the research results to establish a variable temperature accelerated evaluation test method program at a very low dose rate,providing a test basis and a theoretical basis for the selection and verification of aerospace devices.