The role of the bottom and top interfaces in the 1st reset operation in HfO2 based RRAM devices

In this work, the increase on the conductive filament conductivity during the 1st Reset operation, by using the incremental step pulse with verify algorithm, in HfO2 based 1T1R RRAM devices is investigated. A new approach is proposed in order to explain the increase of conductivity by highlighting the crucial roles played by both metal-oxide interfaces. The top metal-oxide interface (HfO2−x/TixOy) plays a crucial role in the forming operation by creating a strong gradient of oxygen vacancies in the hafnium oxide layer. The bottom metal-oxide interface (TixOyNz/HfO2−x) also creates oxygen vacancies, which strengthen the conductive filament tip near to this interface at the beginning of the 1st Reset, leading to the reported conductivity increase. After the 1st Reset operation the conductive filament stabilizes at the bottom interface suppressing this behavior in the subsequent reset operations.