Ferroelectric Undoped HfOx Capacitor With Symmetric Synaptic for Neural Network Accelerator

A plasma-based ferroelectric undoped HfO
_x
capacitor is fabricated using plasma-enhanced atomic layer deposition (PE-ALD), and the multilevel characteristics of synaptic behavior are investigated. A gradual ferroelectric phase transition in the material is confirmed by grazing incidence X-ray diffraction (GI-XRD) for different O
₂
plasma periods. The metal-ferroelectric-metal (MFM) capacitor presents excellent remnant polarization (P
_r
) up to 13 μC/cm
²
and a switching endurance of more than 10
⁸
cycles. Superior small potentiation/depression nonlinearity (α
_p
/α
_d
= -0.08/-1.66 for voltage modulation stimulation) for synaptic training and almost symmetry training curve (|α
_p
-α
_d
|) are obtained. High stability under multilevel operation with five consecutive cycles of alternating potentiation and depression is exhibited without significant polarization variation for each training step (pulse).