Immediate Read-After-Write Capability in p-Type Ferroelectric Field-Effect Transistors and Its Evolution With Fatigue Cycling

P-type ferroelectric field-effect transistors (p-FEFETs) are of significant interest due to recent reports on their immediate read-after-write capability (unlike their n-type counterparts), which is of prime importance for high-speed, embedded memory applications. We show, for the first time, that the delay for read to restore the memory window after write (i.e., read-after-write delay,
$t_{d}$
) degrades with continued bipolar stress (voltage cycling) in p-FEFETs, together with memory window
$(\Delta V_{T})$
collapse. We also unravel the physical origin of
$t_{d}$
degradation. We show that post-stress annealing (400°C/30 min in forming gas) leads to a complete recovery of the subthreshold swing and the gate current to pre-stress levels, and partial recovery of
$\Delta V_{T}$
and the remnant polarization–but cannot restore p-FEFET’s immediate read capability. This is suggestive of that bipolar stress induced
$t_{d}$
degradation is associated predominantly with “neutral” traps generated by bipolar stress in the bulk of the gate oxide stack (rather than at the interfaces), as in time-dependent-dielectric breakdown (TDDB).