Insights about reliability of Heterojunction Bipolar Transistor under DC stress

Abstract

250GHz SiGe(C) Heterojunction Bipolar Transistor (HBT) is a high performance device with low noise figure and high transconductance particularly required in power RF circuits. Applications are various: 77GHz automotive radars, non invasive imaging in airport for example. In order to achieve such specification, aggressive design leads to use of HBT at high collector current and sometime with VCE bias higher than collector emitter breakdown voltage with open base BVCEo. This last bias condition is known to induce progressive degradation with time and must be taken into account in Design-in-Reliability model. While reverse mode has been widely investigated, reliability of direct mode biased HBT is a new research field. It has been recently investigated [1,2], the underlying damage physics is now identified, the integrity of EB and BC junctions is known to be impacted as illustrated in the simulation of Fig. 1. The present paper aims at presenting a methodology for characterizing the aging of HBT in time and translating the parameters change of its model card.