Total Dose Effects on Bipolar Integrated Circuits at Low Temperature

Total dose damage in bipolar integrated circuits is investigated at low temperature, along with the temperature dependence of the electrical parameters of internal transistors. Bandgap narrowing causes the gain of npn transistors to decrease far more at low temperature compared to pnp transistors, due to the large difference in emitter doping concentration. When irradiations are done at temperatures of -138^°C, no damage occurs until devices are warmed to temperatures above -50^°C. After warm-up, subsequent cooling shows that damage is then present at low temperature, although it is much less than for room temperature irradiation. This can be explained by the temperature dependence of dispersive transport in the continuous-time-random-walk model, along with the reduction in charge yield at low temperature. For linear integrated circuits, low temperature operation is affected by the strong temperature dependence of npn transistors along with the higher sensitivity of lateral and substrate pnp transistors to radiation damage.