Novel Negative $Vt$ Shift Phenomenon of Program–Inhibit Cell in $\hbox{2}X{-}\hbox{3}X\hbox{-}\hbox{nm}$ Self-Aligned STI nand Flash Memory

A novel program-inhibit phenomenon of “negative” cell
Vt
shift has been investigated for the first time in 2
X
- 3
X
-nm self-aligned shallow trench isolation nand Flash memory cells. The negative
Vt
shift is caused in an inhibit cell when along-word-line adjacent cell is programming. The magnitude of the negative shift becomes larger in the case of higher program voltage (
V
_PGM
), lower field oxide height, slower program speed of the adjacent cell, and high
Vt
of victim cell. The experimental results suggest that the mechanism of negative
Vt
shift is attributed to hot holes that are generated by FN electron injection from channel/junction to the control gate. This phenomenon will become worse with cell size scaling since hot hole generation is increased by increasing the electron injection due to narrower floating gate space. Therefore, this negative
Vt
shift phenomenon is one of the new scaling limiters of nand Flash memory cell, which needs to be managed for 2 and 3 b/cell in 2
X
nm and beyond nand Flash memories.