Resistance Type Storage Device Design, Production And Characterization

As conventional continuous floating gate memory device scaling is expected to face the technical and physical limit in the near future. Some new memory structures and new materials have been proposed in recent years to solve the problem, such as resistive memory device. Resistive random access memory (RRAM) based on a insulting layer such as an oxide in a metal-isolator-metal (MIM) structure has the potential to serve as a possible replacement for conventional floating gate memory due to its simple structure, low operation voltages, simple sensing circuits, low power consumption, and especially due to its suitability for crossbar structures that enable the realization of ultrahigh dense memory arrays.In this work, the resistive switching in NiO thin film in MIM structure is investigated for RRAM applications. A high ratio of high-resistance state (HRS) and low-resistance state (LRS)(≥103) is observed. The device can be switched from LRS to HRS by a pulse of1.2V to3.3V, and from HRS to LRS by a pulse of0.5V to0.9V. More than100repetitive programming/erase cycles are conducted with an on/off ratio of103. After104s there is no obvious change observed in the memory window, indicating a good retention capability.Resistive-switching behaviors of nickel oxide thin films during the set and reset processes have been examined. In the switching from a low-resistance state (LRS) to a high-resistance state (HRS), a preferable reset voltage is observed. In addition, resistance fluctuations can be also observed in a successful or unsuccessful reset switching. These observations suggest that both the formation and deformation of conductive filaments could be involved and compete in the reset process.A write-once-read-many-times (WORM) memory device based on conduction switching of a NiO thin film in a metal-insulator-metal structure is fabricated on a flexible substrate. The device can be switched from a low-conductance state (unprogrammed state) to a high-conductance state (programmed state) with the formation of conductive filament(s) in the NiO layer. The current ratio of the state programmed at3V for1μs to the unprogrammed state is larger than104. And the WORM device exhibits good reading-endurance and data-retention characteristics.The resistive switching device based on a nickel oxide thin film exhibits an inherent learning ability of a neural network. The device has the short-term-memory and long-term-memory functions analogous to those of the human brain, depending on the history of its experience of voltage pulsing or sweeping.