Investigation of the retention performance of an ultra-thin HfO2 resistance switching layer in an integrated memory device

Abstract

The retention behavior of a HfO2 resistive switching memory device with a diameter of 28 nm and an ultra-thin (1 nm) HfO2 layer as the switching layer was examined. Ta and TiN served as the oxygen vacancy (VO) supplying the top and inert bottom electrodes, respectively. Unlike the retention failure phenomenon reported in other thicker oxide-based resistance switching memory devices, the current of both the low and high resistance states suddenly increased at a certain time, causing retention failure. Through the retention tests of the devices in different resistance states, it was concluded that the involvement of the reset step induced the retention failure. The pristine device contained a high portion of VO-rich region and the location of the border between the VO-rich and VO-free regions played the critical role in governing the retention performance. During the reset step, this borderline moves towards the Ta electrode, but moves back to the original location during the retention period, which eventually induces the reconnection of the disconnected conducting filament (in a high resistance state) or strengthens the connected weak portion (low resistance state). The activation energy for the retention failure mechanism was 0.15 eV, which is related to the ionization of neutral VO to ionized VO.

Triggering WORM/SRAM Memory Conversion by Composite Oxadiazole in Polymer Resistive Switching Device

“…In the OFF state of the FTO/PMMA/Ag and FTO/PMMA+oxadiazole/Ag device, the ohmic conduction was observed in a low voltage region, and the slope increased to over 2 (2.94, 1.19, and 3.78), manifesting that the space-charge-limited conduction (SCLC) among the disconnected portion of the conducting filament governs in a high voltage region. These conduction properties in ON and OFF states are also in keeping with those in the previous report [40][41][42].…”

Electrolyte-Dependent Modification of Resistive Switching in Anodic Hafnia

“…Many memristors and ReRAM memories were reported to fail at temperatures above 80 °C due to repeated formation and/or deletion of CFs mainly composed of oxygen vacancies. Their assistance in generating an insulating oxide layer of random nature trigger thermal instabilities of CFs [ 46 ].…”

“…Given the erratic behavior of the following cycles, it may be alleged that irreversible filaments are gradually formed after 1000 cycles inducing a certain device instability. This process is typically related to the diffusion of oxygen vacancies into the CF deletion region [ 46 ]. A certain material fatigue allows the memristor to reform during its lifetime.…”

Composite Memristors by Nanoscale Modification of Hf/Ta Anodic Oxides

“… 16 , 17 , 34 However, the memristors failed after 10 5 cycles during consecutive writing, which was previously explained by the sudden diffusion of O vacancies into CFs increasing the conductance of HRS. 41 …”

“…Previous studies confirmed that a sudden diffusion of O vacancies into the CF ruptured region during the switching repetition may decrease the HRS values and cause device failure. 41 Hence, the random nature of CFs growth may increase the probability of such detrimental events and thus must be avoided. Controlled O vacancies generation is a critical factor in switching uniformity and reproducibility.…”