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 ( {\text{P}}_{r} ) up to 13~\mu \text{C} /cm 2 and a switching endurance of more than 10 8 cycles. Superior small potentiation/depression nonlinearity ( \alpha _{p}/\alpha _{d} = -0.08 /−1.66 for voltage modulation stimulation) for synaptic training and almost symmetry training curve ( \vert \alpha _{p} - \alpha _{d}\vert ) 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).