Optimized Method for Low‐Energy and Highly Reliable Multibit Operation in a HfO2‐Based Resistive Switching Device

Abstract

Abstract Here, an optimized method for energy‐efficient and highly reliable multibit operation in a Au/Al2O3/HfO2/TiN resistive switching (RS) device is investigated. A thin Al2O3 layer inserted between the top electrode and the HfO2 RS layer in a capacitor‐like RS device plays the role of an electrical resistor and modulates the external bias‐dependent resistance variation behavior of the RS device. Compared to the case where a single HfO2 layer is used, the device with a Al2O3/HfO2 stacked layer shows slow and nonvolatile resistance state variation with a stepwise increase of the applied voltage, which can significantly reduce the occurrence frequency of the abnormal cases during the incremental‐step‐pulse‐programming (ISPP) and error‐check‐and‐correction (ECC) processes. This phenomenon reduces the number of ISPP/ECC sequences, which is advantageous for achieving energy‐efficient programming in the multibit operation of an RS device. To clarify the role of the Al2O3 thin film layer, a comparative study is performed with an Au/HfO2/TiN stacked device and a serially connected external load resistor. The observed behavior is consistent with that of the device with an Al2O3 layer. This study demonstrates that the simple insertion of an insulating layer in an RS device can facilitate reliable and energy‐efficient multibit operation for future nonvolatile memory applications.

Keywords

• error check and correction (ECC)
• HfO2
• incremental step pulse programming (ISPP)
• low energy
• multibit operation
• number of ISPP/ECC sequence (NIES)