Effect of crystallinity on endurance and switching behavior of HfOx-based resistive memory devices

This paper compares the resistive switching properties of crystalline and amorphous HfO
_x
thin-film resistive memory devices (RMDs), which were fabricated by physical vapor deposition films using two different O
₂
partial pressures. The crystallinity of the two HfO
_x
samples was verified by X-ray diffraction (XRD) and transmission electron microscopy (TEM). Ni/HfO
_x
/Cu devices fabricated from both 50 nm thick amorphous and crystalline HfO
_x
films exhibited consistent bipolar switching. Average electroforming voltage for the crystalline and amorphous weare <;20 V and <;11 V, respectively. Both devices showed similar average set (V
_set
) and reset (V
_reset
) voltages of -2.25 V and 0.35 V, respectively, independent of electrode size and current compliance. Preliminary endurance data shows that the amorphous device shows the better endurance (14,300 cycles) compared to that of the crystalline device (102,000 cycles), which is at about an order of magnitude higher than the endurance of the crystalline device. Switching uniformity for both devices showeds similar trends with dispersions (standard deviation/mean ratio) of about 30% for V
_set
and V
_reset
.