Abstract
The effects of proton irradiation on SiGe HBTs implemented with isolation guard rings are investigated in this work. Different from what was shown in any of the previous radiation tolerance studies, a distinctive increase of the emitter current after proton irradiation was observed on a measured inverse-mode Gummel plot from the SiGe HBTs implemented with isolation guard rings. Detailed device measurements and modeling revealed a new SiGe HBT degradation mechanism under proton irradiation. It is found that the increase of the emitter current measured in the inverse-mode Gummel plot comes from the degradation of the substrate–collector (buried layer) junction diode associated with the SiGe HBTs. Furthermore, we identified that the radiation damages in the substrate–collector junction near the deep trench edges are solely responsible for the observed degradation of radiation tolerance. The potential impact of this radiation damage to device operation is discussed.
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