Proton Irradiation Effects in Mos and Junction Field-Effect Transistors and Integrated Circuits

Because of the application of field-effect transistors, and integrated circuits in space electronic systems and the fact that proton irradiation data at energies typical of a space environment are not extensive, an experimental evaluation of these devices has been conducted. Thee important electrical parameters of these devices were measured before, during, and after irradiation at the Oak Ridge National Laboratory´s 22-Mev Cyclotron. The results obtained from the MOS field-effect study show that their degradation processes include that of charge storage in the silicon dioxide insulating layer and radiation-induced changes in surface states. MOS transistors have been found to degrade at orders of magnitude less integrated proton flux than many bipolar and junction field-effect transistors; therefore, for space applications in radiation fields such as Van Allen Belts and solar particle events, these devices may be subject to serious radiation damage. The junction field-effect transistor desplays a large initial spread in device irradiation response. However, it appears to possess a high degree of resistance to proton irradiation. The integrated circuits tested were of the monolithic type and under proton irradiation displayed a large reduction of minority carrier lifetime in the base region of the circuit transistors. Other less important defects are reduction of free carrier concentration and reduction in mobility. Important electrical parameters that are affected by radiation are imput threshold voltages, output low level voltages, leakages currents, and transient characteristics. In conclusion, MOS field-effect transistors and integrated circuits display significant damage characteristics when subjected to a space proton environment.