Metal-Insulator-Metal (MIM) structures can exhibit memristive properties under appropriate biasing conditions. This phenomenon is based on the resistive switching effect, which is characterized by a pinched hysteresis I-V loop associated with reversible changes in the device resistance caused by an electrical stimulus. This technology is currently under extensive investigation for a wide number of applications such as non-volatile memories, digital logic circuits, hardware security, and brain-inspired computing architectures. In recent years, the influence of electrical stress on the reliability of memristors has been investigated [1,2]. However, the existing literature is limited to the analysis of physical damage resulting from electrical stress, especially in connection with catastrophic dielectric breakdown in resistive switching devices [3,4]. But several questions remain unclear, specifically about the impact of electrical stress and polarity effects in filamentary MIM-based memristors.

This work investigates the consequences of catastrophic damage in TiN/Ti/HfO₂/W memristors subjected to electrical stress. The analysis includes physical inspections and compositional evaluation of the device, employing scanning electron microscopy (SEM) (Fig.1) and energy-dispersive X-ray spectroscopy. The impact of voltage polarity on the observed effects is also discussed. Results indicate that under high negative voltages applied to the TiN top electrode, a worm-like pattern emerges over the active area of the devices (Fig. 1(a)). Additionally, occasionally, more severe damage occurs, characterized by disconnection and melting (Fig. 1(c)). In contrast, no damage is observed in devices subjected to positive polarity stress. In summary, this study contributes to the understanding of the consequences of catastrophic dielectric breakdown in TiN/Ti/HfO₂/W memristors under electrical stress, shedding light on the dynamic interplay between voltage polarity and the physical integrity of the devices.

Fig. 1. SEM images of the damage typologies observed during the physical inspection of the devices subjected to electrical stress under a DC voltage sweep with negative polarity. (a) The most common damage pattern observed (“the worm”). (b) Damage observed at the edge of the top metal line of the device. (c) Image of a melted device, leading to an electrical disconnection.