Study of Hole Traps in the Oxide-Nitride-Oxide Structure of the SONOS Flash Memory

Abstract

The origin and the locations of the hole traps in the oxide-nitride-oxide (ONO) structure fabricated on a p-type Si substrate were investigated by using capacitance-voltage (C-V) and deep level transient spectroscopy (DLTS) measurements. The C-V loop was used not only to evaluate the memory effect of the ONO capacitor but also to determine suitable bias conditions for DLTS. Then, hole traps were found to be distributed over energy levels of 0.49 similar to 0.64 eV above the valence band maximum of Si and their origin was attributed to a combination of nitride and the SiO2/Si interface by using small-pulse DLTS and filling -bias- dependent DLTS techniques.