|Place of Conferral||北京|
|Keyword||双极晶体管 剂量率效应 低剂量率损伤增强效应 损伤机制 变温加速评估方法|
Enhanced low-dose-rate sensitivity (ELDRS), with more degradation occurring at low dose rate for bipolar transistors and integrated circuits (ICs), is considered to be one of the major concerns for total ionizing dose hardness-assurance testing intended for space missions. The most recent degradation models, it is generally accepted that the shape of degradation with ELDRS vary with the total dose, exhibiting threshold trend, linear trend, saturated trend. Further, previous studies suggest that the degradation of devices correspond to a saturated trend for the higher target dose or lower dose rate (<10mrad(Si)) irradiation conditions. However, the recent studies have reported that there is an enhancement phenomenon to occur in that case, but not the shape of saturation. In addition, high-reliability and long-life aircraft is necessary to improve the capability of deep-space exploration. Moreover, because of the variety in processing techniques for bipolar devices, such as oxide thickness, passivation materials, and the amount of hydrogen in packaging, radiation-tolerance testing of ELDRS parts can be complex and difficult. Thus, There must be an understanding of the mechanisms occurring for a higher target dose, to improve the radiation hardness assurance design and testing.Considering the issues related to the TID and hardness-assurance testing on the bipolar devices, the effects of dose rate on the radiation response of the bipolar transistors and linear ICs are examined for the higher target doses in this thesis.The experimental results submitted to various dose-rate irradiation, demonstrate that all of the experimental devices exhibit serious dose-rate effect, showing an enhanced degradation with the dose accumulation. Based on the analysis of the enhanced factor of the TID, the decreased dose rate results in enhanced degradation, and the damage sensitivity of the dose rate is related accumulated dose. Combining the influence of temperature and hydrogen concentration on radiation response, the key physical mechanism responsible for those effect are revealed, and the main reason for this correlation between dose and dose-rate effect is found to be the hydrogen molecules cracking mechanism. This research results provide the reference for the accelerated evaluation method.To fully understand the mechanism at play when the switched temperature irradiation applied, the specially designed gate-controlled lateral PNP transistors (GLPNP) that used to extract the interface traps (Nit) and oxide trapped charges (Not) are examined under various irradiation configurations. Based on analysis of the variations of Nit and Not, with temperature irradiation, suggest that the primary mechanisms for temperature switching irradiation (TSI) as an ELDRS test sequence are the accelerated liberation of protons and formation of Nit, which are key mechanisms in ELDRS. Firstly, the higher temperature accelerates the liberation of protons to form Nit, resulting in enhanced degradation at low dose level. Secondly, the moderate temperature limits protons loss in hydrogen dimerization and has the benefit of Nit buildup. Thirdly, noting that annealing effect and hydrogen dimerization are enhanced, further reduction in irradiation temperature suppress those effects. Therefore, with decreasing temperature irradiation, the Nit and Not at first higher temperature bring some positive influences on the evolution of Nit at subsequent low temperatures.Testing with temperature irradiations submitted to various dose rates, it is observed that the dose rate has influence on magnitude of the degradation, but not the shape of the curve trend. Moreover, the increased hydrogen dimerization, relative to the proton concentration, results in that the temperature corresponding to the peak degradation will move towards the lower temperature when the dose increases. Based on the impact of temperature, dose and dose rate on TID response of devices, the temperature switching irradiation as a ELDRS testing for a target dose of ~ 200krad(Si) has been first proposed in this thesis. This procedure has been experimentally verified by several types of devices, and provide sufficient bound to evaluate ELDRS. Further, it is first attempt to shorten irradiation time from 5 months to 11 h. To conclude, the total ionizing dose effects of the bipolar transistors and ICs are investigated, and extensive experimental research has been shown to develop the physical mechanism of ELDRS. Mover, applying those research results obtained from bipolar transistors and ICs with different irradiation conditions, the theoretical model of the temperature switching approach and the accelerated estimation of ELDRS procedure for higher target dose has been proposed in this thesis.
|李小龙. 高总剂量水平双极器件剂量率效应及加速评估试验方法的研究[D]. 北京. 中国科学院大学,2018.|
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