Mechanism of anomalous recovery in advanced SiGe bipolar transistors after low dose rate irradiation for very high total doses
Section snippets
Introduction and background
Silicon–germanium heterojunction bipolar transistors (SiGe HBT) are an attractive candidate for operation in extreme environments including front-end electronics for high energy physics experiments such as at the Large Hadron Collider at CERN [1], [2]. It makes use of their advantages of high gain and high speed at relatively low power consumption. A significant radiation tolerance is one of the main requirements for using these devices for Physics experiments. Front-end electronics for the
The mechanism of anomalous recovery
The degradation of the bipolar transistor current gain and the increase in base current density JB is caused by the accumulation of radiation-induced positive oxide trapped charge Qot and interface trap densities Nit in the silicon base-emitter spacer-oxide. For qualitative analysis it can be supposed that excess base current density ΔJB increases (thus normalized current gain βN decreases) with increasing oxide trapped charge Qot and interface trap densities Nit. The value of ΔJB and βN
Future directions
Two orders of magnitude reduction of dose rate in [3] (from 25 rad(SiO2)/s to 0.25 rad(SiO2)/s) leads to relatively small reduction of maximum oxide charge, interface traps and excess base current. It can be connected with the Radiation Induced Charge Neutralization (RICN) effect [10] when the time constant of positive charge annealing can be significantly reduced due to positive charge annealing by radiation induced electrons. The problem of the RICN effect demands special analysis.
In Fig. 4 the
Conclusion
The physical mechanism of SiGe bipolar transistor current gain recovery during low dose rate irradiation after absorption of high 60Co gamma dose in the range of 30 Mrad(SiO2) to 50 Mrad(SiO2) is presented. Anomalous recovery is related to the dependence of maximum saturated oxide trapped charge and interface trap densities on dose rate. Using a qualitative model of accumulation and annealing of oxide charge Qot and interface traps Nit, it was shown that reducing dose rate leads to reducing the
Acknowledgement
The authors thank A.T. Yastrebov for technical support. This work is supported and financed in part by the Spanish Ministry of Economy and Competitiveness through the Particle Physics National Program (ref. FPA2012-39055-C02-02) and co-financed with FEDER funds.
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Comparison of holes trapping and protons transport induced by low dose rate gamma radiation in oxide on different SiGe processes
2019, Microelectronics ReliabilityCitation Excerpt :SiGe HBTs used in previous ELDRS studies are all with STI isolation structure and manufactured by IBM process, and the ELDRS effect of this SiGe process are found to be nearly nonexistent. However, another experiment shows that SiGe processes with LOCOS isolation structure experience more significantly ELDRS effect than that of SiGe HBTs with STI isolation structure and exhibit a “true” dose rate effect. [4–8]. The mechanism of ELDRS is very complex depends on a number of factors, such as final passivation, packaging, bias conditions and dose rate [9–11].
Dose rate switching technique on ELDRS-free bipolar devices
2016, IEEE Transactions on Nuclear Science