Microcircuit Hardening Study

The primary purpose of this study Is to evaluate methods of hardening monolithic Integrated circuits to transient ionizing radiation. This is done by (1) controlling the maximum amount of transistor primary photocurrent through controlled variations In the doping profile, and (2) evaluating different fabrication processes for similar circuits. It Is found that photocurrents for similar geometry transistors can be controlled over a range of better than 2:1 with doping variations. Microcircuit output response can be varied over a range of 10:1 with different fabrication processes. Transistor profiles are evaluated using a computer program developed to predict primary photocurrent. Circuit fabrication variations are: diffused and thin-film resistors, oxide isolation, and p-n junction isolation. The circuit design technique using diode compensation of primary photocurrents is investigated. Oxide isolation was the fabrication process that was the hardest to transient radiation for these particular circuits.