Impact of Passivation Layers on Irradiation Response of PNP Transistors Under Different Dose Rates

In this paper, the effect of nitride passivation layer on the irradiation response of PNP bipolar junction transistors (BJTs) by Co-60 gamma ray under high and low dose rates is investigated. In order to analyze the damage mechanisms on BJTs with or without nitride passivation layer induced by gamma rays, the excess base current and deep level transient spectroscopy are measured. Experimental results show that there is an enhanced low dose rate sensitivity for PNP transistors with and without nitride passivation layers. In addition, the degradation of PNP BJTs with nitride layer is more serious than that of PNP BJTs without nitride layer under the same irradiation condition. Compared with the PNP BJTS without nitride passivation layer, ionization effect in the PNP BJTs with nitride passivation layer can generate greater density of interface traps with deeper energy level at a given dose rate. Moreover, the irradiated BJTs under the low dose rate produces deeper energy level of interface traps than that under the high dose rate. Based on the analysis, hydrogen is an important factor influencing the dose rate sensitivity and the degradation of the BJT with nitride passivation layers.