TY  - THES
AU  - Kim, Wonjoo
TI  - Investigation of switching mechanism in Ta$_{2}$O$_{5}$-based ReRAM devices
VL  - 50
PB  - RWTH Aachen
VL  - Dissertation
CY  - Jülich
M1  - FZJ-2017-07303
SN  - 978-3-95806-261-0
T2  - Schriften des Forschungszentrums Jülich. Reihe Information / Information
SP  - II, III, II, 138 S.
PY  - 2017
N1  - RWTH Aachen, Diss., 2017
AB  - Redox-based Restive Random Access Memory (ReRAM) has recently receivedstrong attention due to its potential payout toward high density, low-cost,low-energy NVMs. Development and understanding of Ta$_{2}$O$_{5}$ based ReRAM devices in this research work have been made under following experiments, (i)Ta$_{2}$O$_{5}$ switching layer, (ii) ohmic electrode, (iii) Forming-free ReRAM devices, (iv)ReRAM and MOSFET integration, and (v) implementation of modular arithmetic function. In order to optimize the Ta$_{2}$O$_{5}$ switching layer, various approaches such as the effects of RF sputtering power in Ta$_{2}$O$_{5}$ deposition, the thickness effect of Ta$_{2}$O$_{5}$ switching layer, and the Bi-layer (Ta$_{2}$O$_{5}$ /TaO$_{x}$) structure have been made. The optimized 7 nm-thick Ta$_{2}$O$_{5}$ ReRAM device shows lower VFORM (1.8 V), reasonable V$_{S}$ET (0.8 V) with large memory window (R$_{OFF}$ /R$_{ON}$ >300 at V$_{RESET−STOP}$ =-2.0 V), stable endurance up to 106 cycles (@1.0 μs) and goodretention at 125 $^{\circ}$C for 10$^{4}$ seconds. Further, defect density in the switching oxide can also affect the switching properties of ReRAM devices and a modulation of defect density is possible by deposition rate variation. The layer deposition rate changes depending on RF sputtering power of Ta$_{2}$O$_{5}$ layer. The best RF power condition (236W) at given layer thickness (7 nm) was found in terms of memory window (R$_{OFF}$ /R$_{ON}$ > 800 at V$_{RESET−STOP}$ = -2.2 V) with high reliability (retention and endurance) performance. By introducing optimal Bi-layer (Ta$_{2}$O$_{5}$ /TaO$_{x}$) stack in Ta$_{2}$O$_{5}$ ReRAM device, the R$_{OFF}$ performance further improves with 7.0 nm-thick Ta$_{2}$O$_{5}$ / 20 nm-thick TaO$_{x}$ at low I$_{CC}$ level (50 μA) due to a better control of defects in the Ta$_{2}$O$_{5}$ switching layer. However, the V$_{FORM}$ of the Bi-layer increases from 1.8 V to 3.8 V in spite of highly conductive nature of TaO$_{x}$ layer. [...]
LB  - PUB:(DE-HGF)3 ; PUB:(DE-HGF)11
UR  - https://juser.fz-juelich.de/record/838779
ER  -