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DS: Fachverband Dünne Schichten

DS 39: Resistive Effects I

DS 39.5: Talk

Thursday, March 10, 2016, 10:30–10:45, H8

Influence of Stack Order on the Forming and Switching Behavior of HfO₂/TiO₂ Bilayer Cells for ReRAM Applications — •Alexander Hardtdegen, Hehe Zhang, and Susanne Hoffmann-Eifert — Peter Grünberg Institut (PGI-7) and JARA-FIT, Forschungszentrum Jülich, 52425 Jülich, Germany

In this study we investigate the potential of HfO₂/TiO₂ bilayers composed of 3 nm thin ALD films for application in resistive devices. Special focus is on the influence of the stack sequence on the forming and switching behavior of nano crossbar structures of 100 x 100 nm² area. The Pt bottom electrode serves as inert layer, while sputtered Ti and Hf are chosen as oxygen exchange layers (OEL), depending on the top layer of the oxide film stack, TiO₂ and HfO₂, respectively.

The stack order and the OEL layer show influences on the forming and switching properties of the cells. Stacks with Pt/HfO₂/TiO₂/Ti exhibit a forming voltage of 2.65 V which is significantly higher as the value of 1.90 V obtained for the stack with Pt/TiO₂/HfO₂/Hf, although the thicknesses of the oxide layers are identical. After forming into the ON state and subsequent reset, both cells show stable bipolar resistive switching with SET voltages lower than 1.0 V. A resistance ratio of about 100 is obtained for an operation current of about 300 µA with ON and OFF resistances of 1-5 kΩ and 100-300 kΩ, respectively. For current compliances higher than 500 µA, the devices of both stacks show self-limited switching behavior. Additionally, devices were switched with voltage pulses of about 100 ns. Dependencies of the switching time on the switching voltage and power are discussed.