Effect of Ti buffer layer on HfOx-based bipolar and complementary resistive switching for future memory applications

Abstract

Resistive switching memories (RRAM or ReRAM) based on transition metal oxides (TMOs) have been widely investigated as a future nonvolatile memory (NVM) candidate with encouraging potential to serve both embedded and standalone applications, due to its simple structure/ fabrication process, low power consumption, multibit operation and high density scaling while maintaining high switching speed, endurance, high temperature retention etc. [1-2]. Among the several proposed materials for RRAM, HfOx is one of the most representative candidates due to its superior electrical performances and excellent compatibility with current CMOS technology [3-5]. The most commonly accepted switching mechanism in RRAM is the formation and rupture (ON and OFF) of conducting filament based on oxygen ion or oxygen vacancy migration within the TMOs. Since oxygen vacancies play a crucial role to change the resistance states (high or low) under the presence of electric field within the TMOs. Therefore, numerous research efforts have been focused on the technical improvements to control the oxygen vacancy concentrations [6-8]. In the previous work, we demonstrated that the HfOx based RRAM device with oxygen atom gettering Ti layer in Ti/HfOx stack showed tremendous electrical performances in terms of lifetime and performance of the memory for the single and 1-kb array devices [3-4]. In this work, we further propose an effortless Ti thickness modulation based methodology to control the oxygen vacancy concentrations in HfOx layer. This approach is demonstrated to control the forming voltage or leakage current, decrease the operation current, and controllable bipolar and complementary resistive switching (BRS and CRS) properties in HfOx based RRAM devices.