Chao-Cheng Lin

Resistive Switching Mechanisms ofV-Doped

The resistive switching behaviors of sputtered V-doped SrZrO3 (V:SZO) memory films were investigated in this letter. The current states of the memory films were switched between high current state (H-state) and low current state (L-state). The resistance ratio of the two current states was over 1000 at a read voltage. The switching mechanism from L- to H-state corresponds to the formation of current paths. However, this mechanism from Hto L-state is thought to be due to the fact that the defects present in the V:SZO film randomly trap electrons, and hence, the current paths are ruptured. The conduction mechanism of the H-state is dominated by ohmic conduction, whereas the L-state conduction is dominated by Frenkel-Poole emission. The polarity direction of the resistive switching is an intrinsic property of the SrZrO3 oxides. The V:SZO films with high uniformity and good stability are expected to be used in nonvolatile memory

hboxSrZrO_3

The resistive random access memory has attracted much attention for nonvolatile memory application in recent years. However, there is an issue about variations of switching parameters such as set voltage and conductivity of resistance state in resistive switching memory. The variations may cause not only switching error but also reading error during operation. We investigated the switching performance of binary metal oxide as a resistive switching layer embedded with and without metal nanocrystals. Compared with the conventional memory structure, the memory embedded with metal nanocrystals shows better stability, preferable uniformity for the next generation nonvolatile memory application.

Memory Films

In this paper, the influence of a 600 °C rapid thermal annealing for 60 s on the improvements of resistance switching behaviors in a TiN/SiO2/FeOx/FePt structure is reported. It is found that besides the distinct reduction in memory switching parameters in forming voltage, set/reset voltages, and their dispersions, the resistance ratio of high-resistance state to low-resistance state is also enlarged after annealing. The effects of annealing on improving the resistance switching properties are discussed by x-ray diffraction and x-ray photon-emission spectra depth profile results. Additionally, good retention characteristics are exhibited in the annealed TiN/SiO2/FeOx/FePt resistance switching memory.

Influence of Nanocrystals on Resistive Switching Characteristic in Binary Metal Oxides Memory Devices

An oxygen incorporated Mo silicide was explored to form the Mo nanocrystals after rapid thermal annealing. Transmission electron microscopy showed the nanocrystals embedded in SiOx. Charge storage characteristics of Mo nanocrystals influenced by the Mo oxide and the surrounding oxide were investigated through x-ray photoelectron spectroscopy and the electrical measurement. X-ray photoelectron spectra analyses revealed the redox reaction in the oxygen incorporated Mo silicide layer after rapid thermal annealing. The memory window and retention were improved due to reduction in Mo oxide.

Improvement of resistance switching characteristics in a thin FeOx transition layer of TiN/SiO2/FeOx/FePt structure by rapid annealing

The resistive switching properties of the sputter-deposited SrZrO3 (SZO) memory films were investigated in this study. The resistive switching behaviors of the SZO film can be improved by doping with vanadium oxide. The conduction mechanisms of the high and low current states of the 0.3% V-doped SZO (V:SZO) film are ohmic conduction and Frenkel–Poole emission, respectively, which implies the bulk effect of the memory film. The resistive ratio of two current states of the 0.3% V:SZO film remains 1000 times after applying 100 voltage sweeping cycles. Furthermore, the 0.3% V:SZO film shows stable resistive switching properties when measurement is performed at 100 °C. The band modulation of the SZO/LNO interface is proposed to explain the forming process of the SZO films. The 0.3% V:SZO memory film has excellent properties, such as high stability, good endurance, and long retention time, which make it a good candidate for next-generation nonvolatile memory application.

Charge storage characteristics of Mo nanocrystal dependence on Mo oxide reduction

We investigated ammonia plasma treatment influence on the nonvolatile memory characteristics of the charge storage layer composed of Mo nanocrystals embedded in nonstoichiometry oxide (SiOx). X-ray photoelectron spectra analyses revealed that nitrogen was incorporated into the charge storage layer. Electric analyses indicated that the memory window was reduced and the retention and the endurance improved after the treatment. The reduction in the memory window and the improvement in retention were interpreted in terms of the nitrogen passivation of traps in the oxide around Mo nanocrystals. The robust endurance characteristic was attributed the improvement of the quality of the surrounding oxide by nitrogen passivation.

Resistive switching properties of SrZrO3-based memory films

Co nanodot memory devices formed by oxidation processes were studied. Transmission electron microscopy and x-ray photoelectron spectroscopy analyses showed that overoxidation of the cobalt and silicon degraded the charge-storage ability seriously. However, a precapped oxide can mildly oxidize the CoSi2 film to protect the overoxidation to occur. In addition, an oxygen-incorporated CoSi2 film is proposed to improve the oxidation process further. Through incorporating the limited oxygen during sputtering process, the Co nanodot memory device obtains a larger memory window. Also, the reliability characteristic of the Co nanodot memory device formed by annealing the oxygen-incorporated CoSi2 film has been demonstrated.

Improved reliability of Mo nanocrystal memory with ammonia plasma treatment

We investigated the formation and charge storage characteristics of Mo nanocrystals in silicon oxide and in silicon nitride by rapid thermal annealing of oxygen- and nitrogen-incorporated Mo and Si mixed layers. A high density of Mo nanocrystal (6 ? 1012?cm?2) was formed in the nitrogen-incorporated layer. Electrical analyses indicated that the memory window of the Mo nanocrystal embedded in the nitride is larger than that in the oxide. A reliability test showed that the Mo nanocrystal in the nitride has better reliability than the Mo nanocrystal in the oxide, which was explained by an electrical field simulation.

Cobalt nanodots formed by annealing the CoSiO layer for the application of the nonvolatile memory

We propose a method to fabricate a Ni nanocrystal structure by simultaneously coevaporating Ni and pellets. An rapid thermal annealing was used to enhance the Ni nanocrystals to aggregate. Transmission electron microscopy indicates that the formed Ni nanocrystals show a high density distribution of about . Then, the memory device using the Ni nanocrystals as charge-trapping centers was fabricated. The Ni nanocrystal memory device has an obvious memory window under capacitance–voltage measurement. X-ray photoelectron spectroscopy confirms the memory effect results from the Ni nanocrystals embedded in the dielectric layer. Moreover, related reliability characteristics have been extracted.

Charge storage characteristics of high density Mo nanocrystal embedded in silicon oxide and silicon nitride

Mo nanocrystal memory was fabricated through annealing the oxygen-incorporated Mo and Si layers. We then investigated the influence an of ammonia plasma treatment on the nonvolatile memory characteristics of a charge storage layer composed of Mo nanocrystal memory embedded in SiOx. Transmission electron microscopy revealed the nanostructure of the charge storage layer, and X-ray photoelectron spectra analyses revealed that nitrogen was incorporated into the charge storage layer. Electric analyses indicated that the memory window reduced, and both retention and endurance improved after the treatment. The reduction in the memory window was attributed to the decrease in charge trapping centers in the surrounding oxide after the treatment. The improvement of retention was interpreted in terms of the nitrogen passivation of traps in the oxide around the Mo nanocrystals. The robust endurance characteristic was attributed to the improvement of the quality of the surrounding oxide by nitrogen passivation.