Effect of Displacement Damage on Tantalum Oxide Resistive Memory
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Effect of Displacement Damage on Tantalum Oxide Resistive Memory Joshua S. Holt1, Karsten Beckmann1, Zahiruddin Alamgir1, Jean Yang-Scharlotta2, and Nathaniel C. Cady1 1 Colleges of Nanoscale Science and Engineering, SUNY Polytechnic Institute, Albany, NY 12203, U.S.A. 2 Jet Propulsion Laboratory, California Institute of Technology, NASA, Pasadena, CA, 91109, U.S.A. ABSTRACT The radiation environment of space poses a challenge for electronic systems, in particular flash memory, which contains multiple radiation-sensitive parts. Resistive memory (RRAM) devices have the potential to replace flash memory, functioning as an inherently radiation resistant memory device. Several studies indicate significant radiation resistance in RRAM devices to a broad range of radiation types and doses. In this study, we focus on the effect of displacement damage on tantalum oxide-based RRAM devices, as this form of damage is likely a worst-case scenario. An Ar+ (170 keV) ion beam was used to minimize any contribution from ionization damage, maximizing the effect of displacement damage. Fluence levels were chosen to generate enough oxygen vacancies such that devices in the high resistance state (HRS) would likely switch to the low resistance state (LRS). More than half of devices tested at the highest fluence level (1.43E13 ions/cm2) switched from HRS to LRS. The devices were then switched for 50 set/reset cycles, after which the radiation-induced resistance shift disappeared. These results suggest that device switching may mitigate radiation damage by accelerating oxygen vacancy-interstitial recombination. INTRODUCTION Existing non-volatile memory, including flash memory that is widely used on space missions, is highly vulnerable to radiation effects. Radiation can create traps within the tunnel oxide of a flash memory cell, allowing stored electrons to leak out of the floating gate, erasing the bit [1]. The charge pumps required to write to flash memory rely on a group of capacitors, which can also accumulate radiation-induced traps [2]. This buildup of radiation damage can render the charge pumps incapable of producing the required write voltage. While techniques exist to mitigate radiation effects, several alternative memory technologies which could replace flash memory have been shown to be inherently radiation tolerant. In particular, resistive memory (RRAM) has been shown to be resistant to a broad range of radiation. RRAM devices switch based on the movement of oxygen vacancies or metal cations within an insulator [3]. The tantalum oxide devices used in this study rely on vacancybased switching (VCM). In this category of devices, tantalum oxide and hafnium oxide are the most commonly used materials for resistive switching, due to a combination of high endurance, and fast switching speed [4-6]. RRAM devices made from both materials have been subjected to a range of radiation experiments, examining the effects of ionization damage and displacement damage on different device configurations. In general, ionization damage, which res
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