Investigation of switching mechanism in HfO_x-ReRAM under low power and conventional operation modes

Low-power resistive random access memory (LP-ReRAM) devices have attracted increasing attention owing to their advantages of low operation power. In this study, a vertical-type LP-ReRAM consisting of TiN/Ti/HfO₂/TiN structure was fabricated. The switching mechanism for LP-ReRAM was elucidated as the conductive filament mechanism for conventional mode, and an interface-type switching mechanism for low power mode was proposed. The analysis of low frequency noise shows that power spectral density (PSD) is approximately proportional to 1/f for conventional operation mode. Nevertheless, for low power mode, the PSD of low resistance state (LRS) is proportional to 1/f, while that of high resistance state (HRS) is clear proportional to 1/f². The envelope of multiple Lorentzian spectra of 1/f² characteristics due to different traps reveals the characteristics of 1/f. For HRS of low power mode, a limited number of traps results in a characteristic of 1/f². During the set process, the number of oxygen vacancies increases for LRS. Therefore, the PSD value is proportional to 1/f. Owing to the increase in the number of traps when the operation mode changes to conventional mode, the PSD value is proportional to 1/f. To the best of our knowledge, this is the first study that reveals the different noise characteristics in the low power operation mode from that in the conventional operation mode.