Proton and neutron radiation effects studies of MOSFET transistors for potential deep-space mission applications

Deep space missions for human and robotic exploration require electronic devices that are tolerant to extend exposure to ionizing radiation, including proton radiation from both galactic cosmic rays and solar protons and energetic neutrons produced by interactions between the primary radiation field and intervening materials. This work presents radiation effects data for two sets of MOSFET transistors of 0.25 and 0.5 micron technologies, including “rad-hard by design” (RHBD) devices such as the Enclosed-Layout-Transistor (ELT), and Active Region Cutout Transistor (ARCT). These devices were exposed to high energy neutrons and protons with doses that are commensurate with long-term deep-space missions. The irradiated devices were evaluated through device failures, shifts in the current-voltage characteristics (I
_d
vs. V
_g
), changes in the saturation currents as observed in I
_d
-V
_d
, and threshold voltage (V
_th
) shifts. The postirradiation device characteristics were monitored for several months to study any possible trends in device behavior. Results indicate that ELT devices are more radiation tolerant compared to other devices regardless of gate oxide thickness, and that the 0.25 um technology devices are more tolerant than the 0.5 um technology devices.