The role of nitrogen doping in ALD Ta2O5 and its influence on multilevel cell switching in RRAM

Abstract

The role of nitrogen doping on the stability and memory window of resistive state switching in N-doped Ta2O5 deposited by atomic layer deposition is elucidated. Nitrogen incorporation increases the stability of resistive memory states which is attributed to neutralization of electronic defect levels associated with oxygen vacancies. The density functional simulations with the screened exchange hybrid functional approximation show that the incorporation of nitrogen dopant atoms in the oxide network removes the O vacancy midgap defect states, thus nullifying excess defects and eliminating alternative conductive paths. By effectively reducing the density of vacancy-induced defect states through N doping, 3-bit multilevel cell switching is demonstrated, consisting of eight distinctive resistive memory states achieved by either controlling the set current compliance or the maximum voltage during reset. Nitrogen doping has a threefold effect: widening the switching memory window to accommodate the more intermediate states, improving the stability of states, and providing a gradual reset for multi-level cell switching during reset. The N-doped Ta2O5 devices have relatively small set and reset voltages (< 1 V) with reduced variability due to doping.

Sputtering-deposited amorphous SrVOx-based memristor for use in neuromorphic computing

“…2(a). The I-V characteristics during the voltage sweeps are indicative of typical bipolar resistive switching behavior [15][16][17][18][19][20] . After the electroforming process, DC voltage sweeping from 0 V → 1 V → 0 V with an I CC of 1 mA resulted in a SET process (i.e., an off-to-on transition) and sweeping from 0 V → −0.7 V → 0 V without an I CC led to a RESET process (i.e., an on-to-off transition).…”

“…This type of multilevel resistance allows the possibility of multilevel storage, which can provide more storage space within a single cell and generate synaptic behavior, leading to material and structural innovation [11][12][13][14] . Thus, researchers have made an effort to realize multilevel storage using a variety of approaches, including heterostructures 15,16 , the insertion of an interlayer 17,18 , and doping techniques 19,20 .…”

Resistive Random Access Memory (RRAM): an Overview of Materials, Switching Mechanism, Performance, Multilevel Cell (mlc) Storage, Modeling, and Applications

“…The MLC characteristics in 1R configuration can be obtained by changing the current compliance (I cc ) during 'set' operation whereas the MLC characteristics in 1-Transistor 1-RRAM (1T-1R) cell structure are controlled by varying the voltage at the gate of the transistor, which enables the control of compliance current (I cc ) during the set operation of a RRAM cell. The typical MLC I-V curves of Ti/Ta 2 O 5 /Pt [127] based RRAM cell are shown in Fig. 11.…”

“…Multilevel characteristics of Ti/Ta 2 O 5 /Pt RRAM obtained by controlling the compliance current. 'Reproduced from[127], with the permission of AIP Publishing'…”

TDDB Mechanism in a-Si/TiO2 Nonfilamentary RRAM Device

“…esistive switching memory is a promising emerging non-volatile memory [1][2][3][4][5][6][7][8]. Good characteristics have been achieved in various binary metal-oxide based devices (RRAM), such as NiO [2], TiO2 [3,4], HfO2 [5,6], and Ta2O5 [7,8].…”