Lumped-Model Analysis of Microcircuit Vulnerability

Ionizing radiation effects in simple monolithic microcircuits have been predicted from the microcircuit geometry, electrical measurements, and basic semiconductor parameters. Using the lumped-model technique, the mathematical model of the microcircuit is derived directly from the electronic characteristics and boundary values of each bulk semiconductor region. Basic parameter values of the circuit model are obtained by correlating calculated results to the experimental data. Ionizing radiation effects are included as the radiation carrier generation per unit volume. Since the ionizing radiation effect is included in terms of the bulk semiconductor parameters, the radiation-inclusive lumped model is a straightforward extension of the electrical model. Results are presented for (a) the large-signal electrical and radiation-induced response of junction-isolated and dielectric-isolated DTL gates and (b) the small-signal electrical and radiation-induced response of a junction-isolated differential amplifier. Calculation of the electrical and radiation-induced responses was enabled with the use of SCEPTRE1 and ECAP2 circuit analysis computer codes, for the gate and amplifier analyses, respectively. Use of lumped models in the classical circuit element computer codes was accomplished by deriving the analogous R-C-I networks corresponding to the lumped-models. Representation of the electrical performance and radiation-induced response of the microcircuits was generally very good. The major source of error in the analysis is in the representation of the diffused resistor photoresponse, which in this case, did not include the effects of interleg coupling and conductivity modulation.