Integration of resistive switching devices in crossbar structures

Nauenheim, Christian

Book	PreJuSER-136215

Integration of resistive switching devices in crossbar structures

Nauenheim, C. (Corresponding author)FZJ*

2010
Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag Jülich
ISBN: 978-3-89336-636-1

Jülich : Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag, Schriften des Forschungszentrums Jülich. Reihe Information / information 10, XII, 142 S. (2010) = RWTH Aachen, Diss., 2009

Please use a persistent id in citations: http://hdl.handle.net/2128/3772

Abstract: Conventional CMOS-technology defined by optical lithography will reach its physical limits within the next years together with technologies adopted for data storage. This work presents and combines the alternative concepts of resistively switching devices, usable as nonvolatile memory elements or switches, and nano crossbar architecture, which defer these physical limits sustainably. The nano crossbar architecture consists of a functional component that is integrated between two perpendicularly crossing metallization lines. This configuration allows for a high integration density due to a minimal footprint of 4 F$^{2}$ (F = minimum Feature size). The basic elements are straight metallization lines with excellent scaling capability and fabricated by competitive technologies such as nano imprint lithography. The functional component can be composed of reversibly switching TiO$_{2}$, which is integrated into metal/ insulator/ metal elements (MIM). This can be operated by corresponding set- and reset- voltages between at least two resistance states, which represent a logic "0" or "1". The state is nonvolatile and can be nondestructively determined by voltages below these programming values. The field of application includes memory matrices, which are also named passive ReRAM (Resistive Random Access Memory), elements of the DRL (Diode-Resistor Logic) and RTL (Resistor-Transistor Logic), as well as router and multiplexer. Because of their passive properties, an active control circuitry, which is currently based upon CMOS, is necessary. For this reason, all materials and fabrication technologies are CMOS compatible. The developed and optimized lift-off metallization in combination with electron beam direct writing is a flexible method to fabricate metallization lines with different metals and with a width of 50 nm. The fabricated devices comprise crossbar arrays with a size of 64 × 64 bit and a 30 nm thermally evaporated electrode of a Pt/ Ti double layer. These were examined in terms of ballistic charge transfer mechanisms, since the dimensions of the conductor were in the range of the electron mean free path. The experimental results could be explained by the models of Fuchs-Sondheimer and Mayadas-Shatzkes. Finally, the metal lines offered a high yield and a good scalability with low resistances per unit length. The TiO$_{2}$ thin film was reactively sputtered or deposited by ALD (Atomic Layer Deposition). Subsequently, the electrical transfer from the insulating to the switching state, also called electroforming, was examined in detail and allowed for a reliable bipolar switching. The required operating voltages and currents of 100 · 100 nm$^{2}$ large cells are 2 V and several 100 $\mu$A, [...]

Keyword(s): RRAM (Resistive Random Access Memory) ; resistive switching ; semiconductor device ; lithography ; nanostructures