Effect of SiO₂ Tunnel Oxide Thickness on Electron Tunneling Mechanism in Si Nanocrystal Dots Floating-Gate Memories

The effect of tunnel oxide thickness on the charging/discharging mechanism and data retention of Si nanocrystal dot floating-gate devices was studied. The key point here is the difference in tunnel oxide thickness. Other parameters that can affect memory properties were carefully controlled. The mechanism of electron discharging was discussed on the basis of the difference in tunnel Sio(2) thickness. Direct tunneling was found to dominate in the 3- and 5-nm-thick SiO2 tunnel oxides. However, Fowler-Nordheim (FN) tunneling affects the electron discharging characteristics of a thicker SiO2 tunnel oxide. It was found that memory properties also strongly depend on tunnel oxide thickness.