Impact of Breakdown Voltage on Gamma Irradiation Effects in 0.13- $\mu \text{m}$ and 0.25- $\mu \text{m}$ SiGe HBTs

We have investigated the ionization damage by
⁶⁰
Co gamma irradiation in 0.13- and 0.25-μm SiGe heterojunction bipolar transistors (HBTs). Both technologies feature high-speed HBTs (HS-HBTs) together with high-voltage HBTs (HV-HBTs). Base current degradation with increasing total irradiation dose is studied. An identical behavior of corresponding HS-HBT and HV-HBT is found for operation in forward mode probing the emitter-base junction. In reverse mode where the collector base junction is determining the base current degradation, HV devices exhibit larger degradation than their HS counterparts. The increased width of the collector-base space charge region in HV devices leads to enhanced interface recombination at the adjacent Si/oxide interfaces and stronger base current degradation. TCAD simulations of device degradation suggest a linear relationship between total irradiation dose and radiation-induced interface state density N
_it
.