Impact of the Ferroelectric and Interface Layer Optimization in an MFIS HZO based Ferroelectric Tunnel Junction for Neuromorphic based Synaptic Storage

The stack structure tuning of the ferroelectric tunnel junction (FTJ) devices is reported based on the ferroelectric (FE) layer thickness and interface layer (IL) type/thickness optimization to maximize the FTJ I-on/I-off ratio. A FE thickness scaling shows a low voltage FTJ operation, further challenged by a diminishing trend in the maximum I-on/I-off ratio due to the thickness dependence of the FE polarization, independent of the IL thickness. The maximum I-on/I-off ratio varies by tuning the IL type (SiO2, Al2O3) and thickness (1 nm, 2 nm), indicating a maximum at the SiO2 (1 nm) IL condition. A stable endurance of 10(4) cycles is limited by the high field/cycles induced IL degradation, a stable FTJ at 10y extrapolated retention time is shown. The FTJ synaptic device operation is reported with insight on the stack structure tuning impact on the synaptic LTP/LTD nonlinearity and maximum dynamic range.