Reliability Of Nand Flash Memory

Abstract

Reliability of NAND flash memory is more interesting than that of other semiconductor devices. Program and erase of NAND flash perform by electron injection and emission to/from floating gate (FG). There are several methods of electron injection and emission. For electron injection, there are two methods, namely channel hot electron (CHE) injection and Fowler-Nordheim tunneling (FN-t) injection. Data retention is degraded by electron and hole traps in tunnel oxide. Detrapping of trapped charges in tunnel oxide is a major root cause of V t shift during the data retention test. Read disturb failure is mainly caused in the erase state after program/erase cycling stress. The stress-induced leakage current (SILC), which is generated by program/erase cycling stress, is major root cause for the read-disturb phenomena. The mechanism of erratic over program is considered to be an excess electron injection at hole trap sites in tunnel oxide.