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.