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Title Enhanced Current-voltage Nonlinearity by Controlling Oxygen Concentration of TiOx Buffer Layer for RRAM Passive Crossbar Array
Authors (Tae-Hyeon Kim) ; (Sungjoon Kim) ; (Kyungho Hong) ; (Hyungjin Kim) ; (Byung-Gook Park)
Page pp.417-425
ISSN 1598-1657
Keywords Resistive random access memory; passive crossbar array; current-voltage nonlinearity
Abstract As a next-generation memory, resistive random access memory (RRAM) is attracting attention for its fast speed and non-volatility. Nevertheless, an additional selecting element is required to solve the sneak path problem. However, nonlinear devices such as transistors and selectors not only degrade density of the RRAM array, but also increase difficulty of 3D integration. Therefore, in this study, we propose a method for improving the current-voltage (I-V) nonlinearity of an Pt/Al2O3/ TiOx/Ti/Pt RRAM. Oxygen concentration was controlled based on electrical flexibility of TiOx encompassing metallic and semiconducting properties; and three devices with different TiOx were fabricated. As the O/Ti atomic ratio increases from 1.31 to 1.74, the enhanced I-V nonlinearity was confirmed, which was also quantitatively verified through fitting with a hyperbolic sine function. Reflecting the measured nonlinearity, RRAM passive array was constructed and its read margin was investigated by SPICE simulation. As a result, it is demonstrated that the read margin was improved by increasing the nonlinearity. For TiO1.74 sample which exhibits the highest nonlinearity, a read margin of 22.97% was achieved in 27 × 27 array size. By increasing the nonlinearity of RRAM devices, it is expected that RRAM passive array can be utilized for future high-density storage class memory.