Improvement of Resistive Switching Characteristics of Titanium Oxide Based Nanowedge RRAM Through Nickel Silicidation

Abstract

Low operation power and high endurance of resistive random access memory (RRAM) as a synaptic device are critical parameters for in-memory computing applications. Yet, high power consumption and reliability issue of silicon bottom electrode (BE) RRAM hinder its commercialization as a synaptic device. In this experiment, we report on the improvement of switching characteristics of silicon BE nanowedge RRAM via the Nickel (Ni) silicidation process. Existing highly doped Si-BE forms a SiO2 interfacial layer (IL) during a switching layer deposition and increases an effective thickness, leading to increased voltage drop within the RRAM device and large cycle-to-cycle variations. By siliciding the Si-BE with Ni, the issue of IL formation is removed and the resistance of metallic NiSi BE is further reduced compared to Arsenic (As <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">+</sup> ) doped Si BE. Both dc and ac analyses of the fabricated NiSi-BE nanowedge RRAM have shown the reduction of overshoot and switching current down to 55% of the original value. Transmission electron microscopy (TEM) and energy-dispersive spectroscopy (EDS) analysis convinced the formation of NiSi BE. In addition, gradual switching characteristics, uniform low resistance state (LRS), and better endurance of NiSi-BE nanowedge RRAM enable the Si compatible approach to fabricate a large-size RRAM cross-point array for utilization in hardware-implemented neuromorphic computing applications.