Performance of Hardened P-MOS Devices in Severe Neutron Environments

P-channel MOS devices with a hardened gate insulator have been irradiated to a combined dose of 2 × 1016 n/cm2 (E>1.5 MeV) and 1 × 108 rads (Si). The resulting degradation in device characteristics is described and compared with that due to gamma radiation alone. Significant neutron-induced channel mobility degradation was observed, but the anticipated changes in source-drain punch-through voltage and body effect due to neutron-induced carrier removal were not observed until subsequent post-radiation annealing. After 1 × 1016 n/cm2 and 1 × 108 rads (Si), the test devices were still operational, with a 50% decrease in drain current and a 4V increase in threshold voltage. The extension of this technology to the fabrication of a 5 ampere power switch and a multiple NOR gate integrated circuit, both hardened to doses above 107 rads (Si), is also described.