Nondestructive Readout of Ferroelectric-Gate Field-Effect Transistor Memory With an Intermediate Electrode by Using an Improved Operation Method

We investigated the reading and writing of ferroelectric-gate field-effect transistor memory with an intermediate electrode (IF-FET) to achieve perfect nondestructive readouts. In the previous operation method, although the difference in output voltage Delta
V

_O
between positive (
P

_r

⁺
) and negative (
P

_r

^-
) remanent polarization memory states was adequate for the first reading time, the nondestructive readout for the
P

_r

^-
state was seriously degraded due to the generation of nonreturning domains. In order to solve this issue, a
P

_r

⁰
memory state was used instead of the previous
P

_r

^-
memory state. The
P

_r

⁰
state was induced by applying a pulse combined with a positive voltage (
V

_W

⁺
) and a negative voltage (
V

_W

^-
).
V

_W

⁺
was to reset the previously written memory states, and
V

_W

^-
was to control the amount of remanent polarization. In addition, in order to extinguish perfectly the nonreturning domains, a negative voltage
V

_R

^-
was applied for data reading, following a positive voltage
V

_R

⁺
, where
V

_R

⁺
was determined for clear decoding. The appropriate heights of the writing and reading voltages were determined individually from the viewpoint of good nondestructive readout and large Delta
V

_O
. As a result, it was verified experimentally that the reading endurance reached more than 10
⁸
cycles and that the retention time of IF-FET at 150
^deg
C was possible to exceed ten years.