Characteristics of a Multiple Alloy Nanodot Memory with an Enhanced Charge Storage Capability

A nano-floating gate memory structure with a controllable large threshold voltage window using the Fowler-Nordheim (FN) tunneling program and erasing is proposed. This structure has multiple dot layers composed of a uniform single alloy dot layer in the surrounding silicon dioxide layer and a uniform interoxide layer between these dot layers. Here, we confirmed that multiple alloy FePt nanodot layers provide more charge storage than a single layer, which gives a larger memory window. Thus, multiple nanodot layers can store more charges corresponding to the number of layers with the optimization of several parameters, such as blocking oxide layer thickness. In addition, high operation voltages, low operation speeds due to a thick blocking oxide layer, and the poor retention related to the device structure were revealed, and the improvement of this issue was also discussed. Despite several issues, it is expected that a multiple FePt nanodot memory using FN tunneling will be a candidate structure for a future flash memory because of its larger memory window. (C) 2010 The Japan Society of Applied Physics