Safe Operating Area from Self-Heating, Impact Ionization, and Hot Carrier Reliability for a SiGe HBT on SOI

A unified electro-thermal safe operating area (SOA) expression is proposed in this paper to evaluate self heating, impact ionization, and hot carrier (HC) degradation effects simultaneously in a full range of bipolar transistor operation. This SOA is demonstrated by experiments for a SiGe hetero-junction bipolar transistor (HBT) fabricated on silicon on insulator (SOI) by extracting principle parameters from discrete transistors and current mirrors. Also, time dependent reliability tests have been fulfilled for several meaningful bias points within this SOA at the fixed V_BE and V_CE. Avalanche induced HC injection was another important factor to restrict device performance. Finally, the modified electro-thermal SOA by HC reliability is suggested here.