Dielectric Morphology and RRAM Resistive Switching Characteristics
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Dielectric Morphology and RRAM Resistive Switching Characteristics G. Bersuker, B. Butcher, D. C. Gilmer, L. Larcher1, A. Padovani1, R. Geer2 and P. D. Kirsch SEMATECH, Inc., Albany, NY 12203, USA; 1 DISMI, Universita di Modena e Reggio Emilia, Italy; 2CNSE, U. Albany, NY 12203, USA [email protected] ABSTRACT The connection between the bi-polar hafnia-based resistive-RAM (RRAM) operational characteristics and dielectric structural properties is considered. Specifically, the atomic-level description of RRAM, which operations involve the repeatable rupture/recreation of a localized conductive path, reveals that its performance is determined by the outcome of the initial forming process defining the structural characteristics of the conductive filament and distribution of the oxygen ions released from the filament region. The post-forming ions spatial distribution in the cell is found to be linked to a degree of dielectric oxygen deficiency, which may either assist or suppress the resistive switching processes. INTRODUCTION The rising requirements for reducing power consumption for mobile applications and convenience-of-use have increased the efforts and focus toward technology development of the non-volatile memories [1]. In this respect, the resistance switching random access memory (RRAM) technology presents an attractive option due to its demonstrated potential for lowcomplexity /high-density/ high-speed/ low-cost /low-energy non-volatile operation and prospective ability to satisfy the requirements of many of the advanced scaled memory system types [2] [3]. Within the large family of the metal-oxide based resistance switching memory schemes, a common characteristic is that their operating mechanisms involve the rearrangement of the dielectric-material atomic-structure (either within the entire cell or locally) rendering it conductive, which is opposite to the current incumbent electron-storage-based memory technologies. Here we focus on the transition metal-oxide (TMO) filament-based RRAM, specifically the bi-polar HfO2-based RRAM, which operates on (i) the repeatable formation/rupture of a localized conductive path (conductive filament, CF) through the TMO dielectric in a MIM capacitor representing the RRAM device and (ii) the unique attribute of area independent resistance. By the nature of its formation, the HfO2-based RRAM filament crosssections can be controlled by dielectric composition and operation conditions [4], which offer promising scaling opportunities promoting HfO2 as one of the strongest RRAM material candidates. One of the major issues with the RRAM devices is variability of their characteristics, both cycle-to-cycle and device-to-device. To optimize RRAM performance from the standpoint of both structural device properties and operation conditions it is imperative to understand the physical processes responsible for device electrical characteristics. Causative connections between electrical measurements and physical properties can be established only by employing simulations, which exp
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