Electron-Beam Damage of Self-Aligned Silicon Bipolar Transistors and Circuits

The susceptibility of modern self-aligned bipolar transistors to damage by energetic electron beams has been studied. Electrons of energies encountered in electron beam testing, electron microscopy, and electron beam lithography, which are below displacement damage threshold, have been used. The change in dc electrical properties has been measured as a function of the electron beam energy and dose. The primary effect of irradiation is a loss of current gain. The damage is shown to be located in the sidewall oxide spacer above the emitter-base junction, and is attributed to interface traps generated in this region. The requirements for annealing the damage have been determined. To assess the effect of electron beam damage on circuits, ring oscillators have been irradiated, demonstrating that in some circumstances, radiation can degrade the average gate delay. © 1991 IEEE