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@PHDTHESIS{Lentz:187988,
      author       = {Lentz, Florian},
      title        = {{I}ntegration of {R}edox-based {R}esistive {S}witching
                      {M}emory {D}evices},
      volume       = {41},
      school       = {RWTH Aachen},
      type         = {Dr.},
      address      = {Jülich},
      publisher    = {Forschungszentrum Jülich GmbH Zentralbibliothek, Verlag},
      reportid     = {FZJ-2015-01477},
      isbn         = {978-3-95806-019-7},
      series       = {Schriften des Forschungszentrums Jülich. Reihe Information
                      / Information},
      pages        = {166 S.},
      year         = {2015},
      note         = {RWTH Aachen, Diss., 2014},
      abstract     = {The steadily growing market for consumer electronics and
                      the rapid proliferation of mobile devices such as tablet
                      computers, MP3 players and smart phones make high demands
                      for the nonvolatile memory. Present FLASH memory technology
                      approaches to the end due to physical scalability limits.
                      Therefore, an alternative technology must be developed. For
                      memory technology, not only the storage density and cost are
                      important factors but the power consumption and the
                      writing/reading speed must also be taken in account.
                      Redox-based resistive memory (ReRAM) offers a potential
                      alternative to the FLASH technology and presently is in the
                      focus of research activities. The operating principle of the
                      ReRAM is based on the non-volatile reversible change in
                      resistance by electrical stimuli in a simple
                      metal-insulator-metal(MIM) device architecture. This simple
                      structure enables the integration of ReRAM in passive
                      crossbar arrays, in which each crosspoint consumes only
                      4F$^{2}$ (F- feature size) device area. This leads to an
                      ultra-high storage density at reduced cost. Research on the
                      ReRAM memory elements requires a technology platform that
                      ensures a cost-effective fabrication of the crossbar devices
                      with nanometer feature size. In this thesis, the fabrication
                      processes have been developed based on the nanoimprint
                      lithography, which facilitates both the high resolution
                      (<50nm) and the high throughput at low cost. The stamp for
                      the UV-nanoimprinting is developed with plasma etching and
                      electron-beam lithography. This process facilitates the
                      fabrication of the ReRAM devices sizes ranging from 40x40
                      nm$^{2}$ to 100x100 nm$^{2}$. The fabricated nano-crosspoint
                      ReRAM of different switching layer thickness and different
                      device areas are electrically characterized. In order to
                      toggle the resistance state in the ReRAM device, an
                      electroforming step is generally required. In this work, a
                      systematic analysis of the electroforming process is carried
                      out on TiO$_{2}$ and WO$_{3}$-based ReRAM cells and the
                      respective switching characteristics are investigated. The
                      switching mechanism is explained by the filamentary
                      conduction model. The forming voltage decreases with
                      decreasing oxide layer thickness whereas it increases for
                      the smaller device size. Due to overshoot phenomena during
                      the electroforming process, these devices show a significant
                      increased switching current, lower non-linearity, and lower
                      endurance. The ReRAM device performance is improved by
                      integration in the backend of a 65nm CMOS process. In the
                      integrated 1T-1R stack, the electroforming is performed by
                      controlling the current flow with the gate electrode. By
                      employing this approach, the switching current in the ReRAM
                      devices is reduced to 1 $\mu$A. In order to lower the sneak
                      path current in the passive crossbar arrays, a high degree
                      of nonlinearity is required. This nonlinearity parameter has
                      been investigated with 100ns transient pulses in the
                      nano-crossbar devices and in the 1T-1R structures. This
                      parameter depends on the switching current and switching
                      material properties. The lower switching current in the
                      TiO$_{2}$ ReRAM leads to the higher nonlinearity.
                      Furthermore, the ReRAM nanodevices inherently exhibit open
                      clamp voltage in the switching characteristics. This
                      phenomenon is explained by the electromotive force(EMF). The
                      amplitude of the generated EMF voltage depends on the nature
                      of the switching materials and can be several hundred mV.
                      This degrades the conducting filament and thereby limits the
                      ON state retention properties of the ReRAM devices.
                      Additionally, the non-zero crossing of the I-V
                      characteristics, caused by the EMF voltage demands the
                      refinement of the memristor theory.},
      keywords     = {Dissertation (GND)},
      cin          = {PGI-7},
      cid          = {I:(DE-Juel1)PGI-7-20110106},
      pnm          = {521 - Controlling Electron Charge-Based Phenomena
                      (POF3-521)},
      pid          = {G:(DE-HGF)POF3-521},
      typ          = {PUB:(DE-HGF)11},
      url          = {https://juser.fz-juelich.de/record/187988},
}