NONVOLATILE MEMORIES USING SINGLE ELECTRON TUNNELING EFFECTS IN SI QUANTUM DOTS INSIDE TUNNEL SILICON OXIDE

摘要

For further memory device scaling in NAND Flash, we investigate new tunneling effects (double junction tunnel) in conventional field-effect-transistor (FET) memories that have charge storage part between channel and control gate. Instead of the silicon oxide tunnel layer between charge storage part and channel, we use double tunnel junction structure, in which Si nanocrystal (Si quantum dot) layer is lying between 2 thin tunnel silicon oxides. As a result of quantum effects in the Si nanocrystals, the memory device characteristics can be improved remarkably, and smaller Si nanocrystal size can lead to better memory characteristics. It is noted that the most significant memory scaling problems (high voltage operations and thick insulators) can be resolved, since Si nanocrystal layer double junction can simultaneously attain low-voltage high-speed w/e, thin tunnel layer thickness and non-volatility, We also show that sub-lOnm device scaling, which is close to the physical limit of scaling, is possible by sub-lnm Si quantum dot size control inside tunnel layer. Thus, small Si dot size control inside tunnel layer is the key issue. It is concluded that Si nanocrystal layer double junction memory realized by further Si dot scaling is a very promising candidate for future memory devices.