Enhancing the Electrical Uniformity and Reliability of the HfO2-Based RRAM Using High-Permittivity Ta2O5 Side Wall

In conventional HfO2-based resistive random access memory (RRAM), SiO2 is usually adopted as side wall spacer (low-k spacer) to define the device feature size. It is found that the forming voltage of the conventional HfO2 RRAM with SiO2 spacer rises when the device size is scaling down from 16.0 μm2 to 0.16 μm2, which is detrimental for application of high density HfO2-based RRAM. In this study, a high permittivity side wall spacer (high-k spacer) Ta2O5 is introduced to replace SiO2 spacer. The Ta2O5 side wall effectively suppress the forming voltage rising issues during RRAM device scaling without introducing costly processing steps. Moreover, compared to the conventional HfO2-based RRAM, the side wall enhanced device exhibits faster switching speed, smaller operation voltage, and higher reliabilities, including endurance and retention. As a result, the use of Ta2O5 side wall significantly enhances the overall switching characteristics of the HfO2-based RRAM device.