Anaylysis of Mechanism about Data Retention Characteristic in Tanos Structure

Recently, as the data usage increases, the memory usage for storing the data also increases. A lot of researches have been done to reduce the production cost of the solid state drive (SSD) using NAND structure, which is widely used as a storage device along with the hard disk drive (HDD). One of them is to change the NAND structure from 2-D to 3-D by using the charge trap flash (CTF) technology, which is using nitride material (i.e., TANOS) in the floating gate instead of the conventional poly-silicon (i.e., SONOS). As the structure and material are changed, the characteristics of the device are also changed. One of the important functions of memory is the ability to preserve the data. Thus, in this paper the long-term evaluation of TANOS structure is investigated and the prediction of retention characteristic can be evaluated through the accelerated tests. We analyzed the behavior characteristics through experiments and Technology Computer Aided Design (TCAD) simulation to improve the accuracy of long-term data retention in TANOS (Tantalum-Alumina-Nitride-Oxide-Silicon) which is one of 3-D NAND. We also examined the effects of time and temperature about data retention by dividing them into four mechanisms: Schottky emission, Fowler-Nordheim (FN) tunneling, Poole-Frenkel (PF) emission, and trap-assisted tunneling.