Electron Irradiation of NPN Bipolar Transistors with Silicon Nitride Passivation

The effect of silicon nitride passivation on the performance of bipolar transistors under ionizing radiation was investigated. Three groups of silicon planar epitaxial npn transistors with silicon nitride, silicon dioxide and composite silicon dioxide-silicon nitride insulating layers were subjected to irradiation by 20 keV and by 1.5 MeV electrons. The base and collector currents were measured as a function of base-emitter voltage. The results show that silicon nitride and silicon dioxide passivated transistors possess identical properties, after irradiation by low energy electrons to saturation, even though the preirradiation d. c. gain of the standard devices was much greater. Irradiation by 1.5 MeV electrons caused channel formation in all three groups.