What are these border traps: introduced by radiation and seen by charge pumping technique?

Currently, there is a great interest in radiation-induced near-interfacial oxide traps (border traps), because it offers a key in degraded modern device technology. Especially, in thinner oxides, where all oxide traps may act as border traps. In addition, gate size can significantly affect the density of border traps in a given device. Moreover, a radiation-induced border-trap study is often required for space application and long-time reliability. In this study, combined voltage- and frequency-charge pumping (CP) techniques were used to investigate the generation and the evolution of border traps as function of total dose in degraded NMOS transistors by using 1.25 MeV ⁶⁰Co γ-rays. In addition, gate length effects on border-trap charge density were discussed. The results show a great correlation between radiation-induced border- and oxide-trap behaviors at low dose rate. This similarity strengthens the idea that both border- and oxide-trap could have the same defect (E´).