A ZnTaOx Based Resistive Switching Random Access Memory

Abstract

The improved resistive switching performance of TaO x by introducing ZnO was reported in this paper. By co-sputtering, the ZnTaO x device shows better endurance, lower operating voltage and more uniform resistance distribution. The improvement is mainly due to the more abundant intrinsic defects such as oxygen vacancies which facilitates the formation of conductive filaments in the oxide compound.Among various non-volatile memory devices, the resistance switching random access memory (RRAM) has outstood for its highdensity storage capability, low operation voltage/current and fast switching speed. Besides those intensively studied oxide materials for the RRAM fabrication, such as TiO 2, 1 NiO, 2 ZnO, 3 HfO x 4 and ZrO 2, 5 recently Ta 2 O 5 or TaO x based RRAM device has been frequently investigated due to its excellent endurance performance and switching speed. Based on the filament dynamic mechanism, both unipolar and bipolar resistive switching (RS) behavior were reported with desirable endurance and retention properties. 6,7 Similar as other oxide-based devices, the formation and rupture of conductive filament (CF) which is related to the chemical composition of oxygen determine the RS behavior in TaO x RRAM. One of the effective ways to obtain better RS performance in TaO x RRAM is how well the oxygen ion or oxygen vacancy concentration is controlled. Therefore, quite some work has been carried out to understand the behavior of oxygen vacancies in resistance switching. For example, F. Kurnia et al. investigated the evolution of oxygen vacancies based CF and achieve the forming-free RS in Pt/TaO x /Pt structure. 8 By applying different voltage on the 1-transistor-1-memoristor (1T1M) device, F. Miao et al. successively tuned the conduction channel in TaO x which related to the oxygen concentration, and obtain varied switching behavior. 9 Moreover, Ta was used instead of Pt as top electrode on TaO x by J. S. Chen's group to form an oxygen vacancy reservoir of supplying or storing the oxygen vacancies at the Ta/TaO x interface, and further realize the multilevel switching property. 10 Here we demonstrate another way to engineer the oxygen vacancies in TaO x and result in better RS performance. By mixing various oxides with TaO x , the concentration of oxygen vacancies could be adjusted, and among them, ZnO shows the best improvement of operation parameters.The simplest metal-insulator-metal (MIM) structure was applied to fabricate the RRAM testing cell. The commercial ITO glass was employed as the substrate and bottom electrode. All the oxide films were deposited by RF magnetron sputtering system. Indium balls pressed on top of the sample were used as the top electrodes. The sputtering power for all oxides (Ta 2 O 5 , ZnO Ga 2 O 3 and NiO) were the same (100 W) and the sputtering chamber was kept in the Ar atmosphere (flow rate 30 sccm) with the pressure of 5 × 10 −3 Torr at room temperature. Besides the pure TaO x device, the TaO x was cosputtered with other 3 targets respectively to form ZnTaO x , GaTaO x and ...

Conduction Mechanism of Valence Change Resistive Switching Memory: A Survey

“…This mechanism could be easily identified whenever Ohmic conduction is observed at low field, followed by power-law dependence (I ∝ V 2 ) of the current density is observed in high field [80][81][82]. In low field regime, the conduction mechanism is dominated by the thermally generated free electrons in the oxide film.…”

Status and Prospects of ZnO-Based Resistive Switching Memory Devices

“…Nevertheless, controlled deposition parameter and post-thermal treatment on resistive layer may be not as effective as doping technique to fully adjust the defect concentration. Various dopant elements, such as Al [ 137 , 175 , 176 ], B [ 177 ], Co [ 138 , 139 , 169 , 178 ], Cr [ 110 , 158 ], Cu [ 87 , 140 , 179 ], Fe [ 180 , 181 ], Ga [ 112 , 182 , 183 ], La [ 144 ], Li [ 184 , 185 ], Mg [ 55 , 111 , 145 , 186 – 190 ], Mn [ 91 , 146 – 148 , 191 – 195 ], N [ 56 , 149 ], Ni [ 196 ], S [ 197 ], Sn [ 90 , 198 ], Ta [ 199 ], Ti [ 150 , 151 ], V [ 85 ], and Zr [ 86 ], that have been reported may exhibit decent switching performance. ZnO-based RRAM with multi-element doping, such as Al-Sn [ 136 , 200 ], Ga-Sn [ 201 ], and In-Ga [ 141 – 143 , 202 – 208 ], is also proposed.…”

Variability model for forming process in oxygen vacancy modulated high-κ based resistive switching memory devices

“…Sputtering is a physically destructive process and it introduces a lot of random defects into the dielectric [24,25] as illustrated in Fig. 6(a).…”