Study of Electron Traps in Silicon Dioxide due to Mobile Sodium Ions at the Si-SiO₂ Interface

Abstract

We have studied electron trapping due to mobile sodium ions in silicon dioxide near the Si-SiO₂ interface using MOS capacitors. After doing a bias-temperature stress, hot electrons were injected into SiO₂ by avalanche injection. The number of trapped electrons, as measured by shifts in flat-band voltage of high frequency C-V curves, is proportional to the sodium ion density. The depth of these electron traps was found by a thermal detrapping experiment to be about 1.2 eV. A possible model for the origin of the mobile sodium-related electron trap is presented.