Anomalous TID Susceptibility on Collector Bias for SOI High-Voltage Polysilicon Emitter Bipolar Transistors

The impact of collector-to-emitter bias on the total ionizing dose (TID) response of high-voltage ( <tex-math notation="LaTeX">BVCEO</tex-math> <tex-math notation="LaTeX">$>$</tex-math> 30 V) NPN bipolar junction transistors on thick-film silicon-on-insulator (SOI) technology is investigated using 10-keV X-rays. The radiation-induced base current increase in forward mode shows independence on collector bias condition during irradiation. However, the excess base current in the inverse mode is significantly suppressed under high collector-to-emitter bias condition in the irradiation procedure. TID irradiation-induced electric degradation behaviors and the corresponding 1/ f noise characteristics reveal that the previously irradiation created traps responsible for device degradation cannot be removed by the high collector voltage. The observed collector bias effect can be attributed to the field-assisted migration of holes captured by shallow oxide traps.