Enhancing the Electrical Uniformity and Reliability of the HfO 2 -Based RRAM Using High-Permittivity Ta 2 O 5 Side Wall

In conventional HfO 2 -based resistive random access memory (RRAM), SiO 2 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 HfO 2 RRAM with SiO 2 spacer rises when the device size is scaling down from 16.0 ${\mu }\text{m}^{2}$ to 0.16 ${\mu }\text{m}^{2}$ , which is detrimental for application of high density HfO 2 -based RRAM. In this study, a high permittivity side wall spacer (high-k spacer) Ta 2 O 5 is introduced to replace SiO 2 spacer. The Ta 2 O 5 side wall effectively suppress the forming voltage rising issues during RRAM device scaling without introducing costly processing steps. Moreover, compared to the conventional HfO 2 -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 Ta 2 O 5 side wall significantly enhances the overall switching characteristics of the HfO 2 -based RRAM device.