Abstract
The latent enhanced low dose rate sensitivity (ELDRS) effect is observed in the double-polysilicon self-aligned (DPSA) technology PNP bipolar junction transistor (BJT) irradiated with a high and low dose rate gamma ray, which is discussed from the perspective of the three-stage degradation rate of the excess base current. The great degradation rate as a result of the high dose irradiation of the first stage is dominantly ascribed to the positive oxide trap charges accumulated during a short irradiation, and then due to the competition between the recombination of electrons and capture of the hole by the traps. It declined sharply into a degradation rate saturated region of the second stage. However, for the low dose rate, the small increase in the degradation rate in the first stage is caused by the holes escaping from the initial recombination and being transported to the interface to form the interface states. Then, the competition between the steadily increasing interfacial trap charge and the continuously annealed shallow level oxide trap charge leads to the stable increase of degradation under low dose irradiation. Finally, in stage three, the increases of the degradation rates for high and low dose irradiation result from the different amounts of the hydrogen molecules generated by the hole reactive with depassiviated Si suspended bonds, which can interact with the deep level defects and release protons, causing an increase of interfacial trap charges with prolonged irradiation.
Highlights
As a state-of-the-art high speed bipolar complementary process, double-polysilicon self-aligned (DPSA) technology has been widely used in high-speed analog integrated circuits
The previous total dose irradiation test results in the literature [6,7] have shown that the direct current gain is the most sensitive parameter of the bipolar device under total ionizing dose radiation, Electronics 2019, 8, 657; doi:10.3390/electronics8060657
The results show damage of the current gain under low dose rate irradiation is greater than that under a high dose rate, the damage of the current gain under low dose rate irradiation is greater than that under a high dose and will resultresult in a potential rate, and will in a potential
Summary
As a state-of-the-art high speed bipolar complementary process, double-polysilicon self-aligned (DPSA) technology has been widely used in high-speed analog integrated circuits. Compared with the traditional bipolar junction transistors (BJTs), DPSA BJTs have a smaller linewidth due to the isolation of local oxidation of silicon (LOCOS) combined with deep trench isolation (DTI). The use of polysilicon emitters can increase the current gain so that the device can achieve vertical scale down without reducing the punch-through voltage of the emitter–collector junction and the loss of the current gain [1,2,3]. The self-aligning structure and DTI can realize the lateral scale down of the device, greatly reduce the area of the device, the circuit, and the corresponding parasitic capacitance, significantly reduce the power consumption delay product of the circuit, and improve the integration level of the bipolar circuit [4,5]. The previous total dose irradiation test results in the literature [6,7] have shown that the direct current gain is the most sensitive parameter of the bipolar device under total ionizing dose radiation, Electronics 2019, 8, 657; doi:10.3390/electronics8060657 www.mdpi.com/journal/electronics
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