Study Of Ionizing Radiation Effects And Accelerated Testing Of Bipolar Transistor

With the rapid development of space industry in china, more problems have appearedbecause of the effect of space environment on electric devices. At present it is on exploratorystage about enhanced degradation in low dose rate irradiation and accelerated testing ofbipolar junction transistors. So the effect of ionizing radiation on BJT is investigatedsystematically from total dose effect and low dose rate effect. And an accelerated methodbased on hydrogen is verified. The thesis work is as follows:(1) A study of total dose effect for BJT. Substrate NPN and substrate PNP were irradiatedby Co60, base current and current gain were tested under different accumulated dose.Experimental results show current gain of NPN reduces1.82times under50rad/s，300Krad;decreases26%under10rad/s，51Krad. Current gain of PNP reduces0.35times under50rad/s，300Krad; drops15%under10rad/s，51Krad. Based on Gummel Poon model in Silvaco,failure mechanism was analysed. As accumulated dose increased, irradiation induced oxidetrapped charges increase, and then depletion area of base-emitter junction is enlarged,whichwill increase the base current and decreased the current gain.(2) A study of ELDRS for BJT. The low dose rate effects test was performed by Co60.Experimental results show that under1rad/s the average amount of degradation is40%higherthan that under10rad/s and50rad/s for NPN and PNP. The ELDRS effect was obviouslysurveyed. Based on two-stage hydrogen theory, more original defects are produced in lowdose rate, and then more interface traps are formed which lead to increased surfacerecombination velocity. As a result, the amount of degradation of current gain in low doserate is higher than that in high dose rate.Furthermore，soak with excess molecular hydrogen as an accelerated method was studiedaccording to two-stage hydrogen model. The content of H+and SiHO+were discovered toincrease one time and1.5times in devices that are soaked with100%molecular hydrogen for48hours. The amount of degradation derived from treated devices after10rad/s radiation wasclose to that from untreated devices after1rad/s radiation. The availability of accelerated testmethod is verified.