Impact of Program/Erase Cycling Interval on the Transconductance Distribution of NAND Flash Memory Devices

This study comprehensively investigates the impact of the time interval (t
_wait
) between program/erase (P/E) cycles on the oxide quality of NAND Flash memory devices. It is observed that, at room temperature, P/E cycles with a shorter t
_wait
yield a better oxide quality than those with a longer t
_wait
. The oxide charge (Q
_T
) evolution by distributed P/E cycles can be well described by an analytical equation through the extension of our previous statistical transconductance reduction (G
_m,max
) method. This equation is characterized by a power of the number of P/E cycles multiplied by an exponential decay term of t
_wait
. The former term is related to the Q
_T
generation, whereas the latter is related to the Q
_T
emission during t
_wait
between cycles. This model allows to evaluate the activation energy for both Q
_T
generation (E
_A,G
) and recovery (E
_A,R
). E
_A,G
is revealed to be a function of the logarithmic scale of t
_wait
, decreasing from 100 to 85 meV for t
_wait
varying from 0.1 to 4 s. Moreover, E
_A,R
is approximately 0.4 eV, which is consistent with the value of electron thermal emission from traps in SiO
₂
.