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@PHDTHESIS{Lentz:463104,
author = {Lentz, Florian},
othercontributors = {Waser, Rainer and Heuken, Michael},
title = {{I}ntegration of redox based resistive switching memory
devices},
volume = {41},
school = {RWTH Aachen University},
type = {Dissertation},
address = {Jülich},
publisher = {Forschungszentrum Jülich, Zentralbibliothek},
reportid = {RWTH-2015-00868},
isbn = {978-3-95806-019-7},
series = {Schriften des Forschungszentrums Jülich : Reihe
Information},
pages = {I, 166 S. : Ill., graph. Darst.},
year = {2014},
note = {Druckausgabe: 2014. - Onlineausgabe: 2015. Auch
veröffentlicht auf dem Publikationsserver der RWTH Aachen
University; Zugl.: Aachen, Techn. Hochsch., Diss., 2014},
abstract = {The steadily growing market for consumer electronics and
the rapid proliferationof mobile devices such as tablet
computers, MP3 players and smart phones makehigh demands for
the nonvolatile memory. Present FLASH memory technology
approachesto the end due to physical scalability limits.
Therefore, an alternativetechnology must be developed. For
memory technology, not only the storage densityand cost are
important factors but the power consumption and the
writing/readingspeed must also be taken in account.
Redox-based resistive memory (ReRAM) offersa potential
alternative to the FLASH technology and presently is in the
focus of researchactivities. The operating principle of the
ReRAM is based on the non-volatilereversible change in
resistance by electrical stimuli in a simple
metal-insulator-metal(MIM) device architecture. This simple
structure enables the integration of ReRAMin passive
crossbar arrays, in which each crosspoint consumes only 4F²
(F- featuresize) device area. This leads to an ultra-high
storage density at reduced cost.Research on the ReRAM memory
elements requires a technology platform that ensuresa
cost-effective fabrication of the crossbar devices with
nanometer feature size.In this thesis, the fabrication
processes have been developed based on the
nanoimprintlithography, which facilitates both the high
resolution (<50 nm) and the highthroughput at low cost. The
stamp for the UV-nanoimprinting is developed withplasma
etching and electron-beam lithography. This process
facilitates the fabricationof the ReRAM devices sizes
ranging from 40x40 nm² to 100x100 nm². Thefabricated
nano-crosspoint ReRAM of different switching layer thickness
and differentdevice areas are electrically characterized. In
order to toggle the resistance statein the ReRAM device, an
electroforming step is generally required. In this work,
asystematic analysis of the electroforming process is
carried out on TiO2 and WO3-based ReRAM cells and the
respective switching characteristics are investigated.
Theswitching mechanism is explained by the filamentary
conduction model. The formingvoltage decreases with
decreasing oxide layer thickness whereas it increases for
thesmaller device size. Due to overshoot phenomena during
the electroforming process,these devices show a significant
increased switching current, lower non-linearity, andlower
endurance. The ReRAM device performance is improved by
integration in thebackend of a 65nm CMOS process. In the
integrated 1T-1R stack, the electroformingis performed by
controlling the current flow with the gate electrode. By
employingthis approach, the switching current in the ReRAM
devices is reduced to 1 µA. Inorder to lower the sneak path
current in the passive crossbar arrays, a high degree
ofnonlinearity is required. This nonlinearity parameter has
been investigated with 100ns transient pulses in the
nano-crossbar devices and in the 1T-1R structures.
Thisparameter depends on the switching current and switching
material properties. Thelower switching current in the TiO2
ReRAM leads to the higher nonlinearity.Furthermore, the
ReRAM nanodevices inherently exhibit open clamp voltage in
theswitching characteristics. This phenomenon is explained
by the electromotive force(EMF). The amplitude of the
generated EMF voltage depends on the nature of theswitching
materials and can be several hundred mV. This degrades the
conductingfilament and thereby limits the ON state retention
properties of the ReRAM devices.Additionally, the non-zero
crossing of the I-V characteristics, caused by theEMF
voltage demands the refinement of the memristor theory.},
cin = {611610},
ddc = {620},
cid = {$I:(DE-82)611610_20140620$},
typ = {PUB:(DE-HGF)11 / PUB:(DE-HGF)3},
urn = {urn:nbn:de:hbz:82-rwth-2015-008687},
url = {https://publications.rwth-aachen.de/record/463104},
}
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