Synthesis of Resistive Memory Oxides by Ion Implantation
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Synthesis of Resistive Memory Oxides by Ion Implantation S.M. Bishop1, Z.P. Rice1, B.D. Briggs1, H. Bakhru1, and N.C. Cady1 1 University at Albany, SUNY, College of Nanoscale Science and Engineering, Albany, NY 12203, U.S.A ABSTRACT In this work, we report on the use ion of implantation to synthesize resistive memory oxides. The surface of copper thin films was converted to copper oxide using oxygen implantation. Devices fabricated from the copper oxide (CuxO) layers exhibited unipolar switching behavior without the need for a forming voltage. Technology scaling was demonstrated by oxygen implanting copper damascene vias. Unipolar switching was observed in via-based devices down to 48 nm. The current-voltage data of devices scaled from 100 μm to 48 nm suggests that the RESET transition is related to localized Joule heating. Tantalum oxide (TaxOy) was also created by oxygen implantation but exhibited bipolar resistive switching. Analysis of the conduction suggests that the difference between the two resistance states in these devices is largely due to a lowering of the Pt-TaxOy Schottky barrier. INTRODUCTION It is well-known that non-volatile flash memory is fast approaching fundamental scaling limits. As a result, replacement memory technologies, like resistance change memory, having increased scalability and non-volatile storage capability are receiving considerable attention. A typical resistive memory device (RMD) is composed of a metal oxide sandwiched (laterally or vertically) between two electrodes and utilizes two resistance states, a high resistance off-state (HRS) and a low resistance on-state (LRS), for its memory function. A variety of techniques have been used to synthesize the metal oxide within RMDs; these include oxidation processes such as thermal and plasma oxidation as well as deposition techniques like sputter deposition and atomic layer deposition [1,2,3]. Ion implantation is uniquely suited as a synthesis technique for making resistive memory metal oxide layers because composition engineering can be achieved by changing the dose (in ions/cm2) and/or the energy. It is well established that large concentrations of defects are created within solids as a result of ion implantation. While deleterious in certain applications, this is potentially advantageous in RMDs because the physical mechanism controlling resistive switching is commonly associated with defects (like vacancies) within the oxide layer [4]. Ion implantation therefore offers the unique potential to engineer the defect concentration in the resulting resistive memory oxide layer. EXPERIMENTAL PROCEDURE Three starting substrates were used in this work: (1) blanket deposited 1 μm thick copper on 300 mm Si wafers, (2) copper filled vias on 300 mm Si wafers, and (3) blanket deposited tantalum on 300 mm Si wafers. See Ref. [5] for more details regarding substrate 3 and Ref. [6] for more details regarding substrates 1) and 2). In general, ion implantation was performed on cleaved samples from each wafer with doses ranging from 1x1015-5x1016/cm
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