Impact of Total Ionizing Dose on Low Energy Proton Single Event Upsets in Nanometer SRAM

The impact of the total ionizing dose (TID) on a low energy proton single event upset (SEU) in a 65-nm static random access memory (SRAM) is investigated based on a low energy proton accelerator. The body potential of the P-well is elevated due to charge depletion along the sidewall of shallow trench isolation (STI) induced by TID irradiation. The radiation-induced narrow channel effect causes a decrease in the area and the thickness of the SEU sensitive volume (SV), further resulting in the low energy proton SEU cross section being lowered in 65-nm SRAM with an external independent power supply of the memory array. The impact of the TID on the low energy proton SEU cross section is dependent on test patterns written to the memory array during TID irradiation and SEU testing. The low energy proton SEU cross section is the highest when the complement test pattern is written to the SRAM memory array during TID irradiation and SEU testing compared with the same and half complement patterns.

I. Introduction

Various kinds of particles such as heavy ions, protons, electrons, etc. exist in space irradiation environments. Single event effects (SEEs) in devices are mainly caused by heavy ions and protons, and the total ionizing dose (TID) effects in devices are caused by ionizing radiation including protons, electrons, and energetic photons. Actually, SEE and TID effects will be exerted on the devices simultaneously. However, the ground tests for these two kinds of effects are usually carried out separately, and hardness assurance of SEE is evaluated without considering the influence of TID. Whether the TID will affect the hardness assurance of the SEE in devices or not has been studied for over 30 years.