A Complete Radiation Reliability Software Simulator

In this paper we describe a simulator which can be used to study the effects on circuit behavior of two radiation phenomena: Single Event Upset (SEU) and total-dose radiation effects. Using this simulator the user can predict the error rate in large circuits due to single event upset. The error rate model described here uses a well established methodology, but for the first time a different choice is made on picking up the sensitive nodes, enabling a quick prediction even for very complex circuits. The simulator predicts circuit behavior after total-dose irradiation using as inputs: The dose rate and the total dose, parameter sets that characterize the transistor response to radiation. and the circuit netlist. The total-dose simulator is based on physical models of the changes in the MCSFET caused by radiation. We quantify the degradation of each MOSFET in a circuit with two parameters and determine the change in the MOSFET characteristics from preirrdiation MOSFET data. Using the “irradiated” MOSFET parameters. we can simulate circuit behavior using an ordinary circuit simulator such as SPICE. With this simulator, one can study how resistant a circuit is to changes due to irradiation and design circuits to be functionally radiation “hard”. The “double-kink” in the MOSFET subthreshold region due to the parasitic effect of the edge transistors can be simulated and the user is advised when leakage current is unacceptably large. The speed degradation of a ring oscillator was simulated and the results compared with actual measured data.