Yi-Ting Tseng

Complementary resistive switching behavior induced by varying forming current compliance in resistance random access memory

In this study of resistance random access memory in a resistive switching film, the breakdown degree was controlled by varying forming current compliance. A SiOx layer was introduced into the ZnO layer of the structure to induce both typical bipolar resistive switching (RS) and complementary resistive switching (CRS). In addition, the SiOx layer-generated vacuum spaces in typical bipolar RS can be verified by electrical characteristics. Changing forming current compliance strikingly modifies the oxygen storage capacity of the inserted SiOx layer. CRS can be achieved, therefore, by tuning the oxygen ion storage behavior made possible by the SiOx layer.

Effects of Varied Negative Stop Voltages on Current Self-Compliance in Indium Tin Oxide Resistance Random Access Memory

We have previously investigated the automatic current compliance property for indium tin oxide (ITO) resistance random access memory (RRAM). Traditionally, for the purpose of protecting RRAM, it is necessary to set equipment current compliance during the set and forming processes of RRAM devices. ITO RRAM devices, however, have an intrinsic capability to limit their current. This letter examines this ITO RRAM current compliance in depth by applying a varied stop-voltage measurement method, where different negative stop voltages were adopted to manipulate oxygen ions. Combined with material analysis and conduction current fitting, a model was established.

Improvement of Resistive Switching Characteristic in Silicon Oxide-Based RRAM Through Hydride- Oxidation on Indium Tin Oxide Electrode by Supercritical CO 2 Fluid

Supercritical carbon dioxide (SCCO2) fluid technology was applied to indium-tin-oxide (ITO) electrode to improve the resistive switching characteristic of silicon oxide RRAM through hydride oxidation for the first time. We found device power consumption can be effectively reduced so that side effects can be also restricted under device operation. By applying SCCO2 fluid, more oxygen ions will be introduced into the ITO electrode and thus the participation of net oxygen ions in the RRAM redox reaction will increase. Fourier transform spectroscopy and X-ray photoelectron spectroscopy were used to confirm hydride oxidation on ITO electrode. Combined with the current fitting results, we proposed a reaction model to explain the improvement of resistive switching in RRAM by SCCO2 fluids.

Resistive Switching Mechanism of Oxygen-Rich Indium Tin Oxide Resistance Random Access Memory

This letter investigates the double-ended resistive switching characteristics of indium tin oxide (ITO) resistance random access memory (RRAM). Resistive switching can be achieved around both the active TiN electrode and the inert Pt electrode. In addition, complementary resistance switching (CRS) characteristics can be observed without current compliance during dc voltage sweep operations. Electrical measurement data fitting results indicate that the oxygen-rich ITO near top and bottom electrodes works as a double-ended resistive switching layer. Based on the analysis of the current conduction mechanism, we propose a physical model to interpret the CRS behaviors in ITO RRAM devices.

Resistance Switching Characteristics Induced by O2 Plasma Treatment of an Indium Tin Oxide Film for Use as an Insulator in Resistive Random Access Memory

In this study, an O2 inductively coupled plasma (ICP) treatment was developed in order to modify the characteristics of indium tin oxide (ITO) film for use as an insulator in resistive random access memory (RRAM). After the O2 plasma treatment, the previously conductive ITO film is oxidized and becomes less conductive. In addition, after capping the same ITO material for use as a top electrode, we found that the ITO/ITO(O2 plasma)/TiN device exhibits very stable and robust resistive switching characteristics. On the contrary, the nontreated ITO film for use as an insulator in the ITO/ITO/TiN device cannot perform resistance switching behaviors. The material analysis initially investigated the ITO film characteristics with and without O2 plasma treatment. The surface was less rough after O2 plasma treatment. However, the molar concentration of each element and measured sheet resistance results for the O2-plasma-treated ITO film were dramatically modified. Next, electrical measurements were carried out to examine the resistance switching stability under continuous DC and AC operation in this ITO/ITO(O2 plasma)/TiN device. Reliability tests, including endurance and retention, also proved its capability for use in data storage applications. In addition to these electrical measurements, current fitting method experiments at different temperatures were performed to examine and confirm the resistance switching mechanisms. This easily fabricated device, using a simple material combination, achieves excellent performance by using ITO with an O2 plasma treatment and can further the abilities of RRAM for use in remarkable potential applications.

The Manipulation of Temperature Coefficient Resistance of TaN Thin-Film Resistor by Supercritical CO 2 Fluid

The manipulation of temperature coefficient of resistance (TCR) in TaN thin-film resistor (TFR) was demonstrated by electrical measurement and analysis through supercritical carbon dioxide (SCCO2) fluid treatment for the first time. The negative TCR value of TaN TFR changes to positive TCR value through annealing process due to the growth and merge of TaNx grain. After SCCO2 treatment, the positive TCR value was changed back to negative TCR value in TaN TFR. The TaN grain boundary isolated by dehydroxyl effect of SCCO2 fluid treatment causes the current conduction mechanism changed to hopping conduction from ohmic conduction.

Ultra-Low Switching Voltage Induced by Inserting SiO 2 Layer in Indium–Tin–Oxide-Based Resistance Random Access Memory

A lower switching voltage of indium-tin-oxide (ITO)-based resistance random access memory (RRAM) with an inserted SiO2 thin film was presented. The amplitude of switching voltage of device was below 0.2 V whether measured by direct current or alternating current sweep operation. Notably, the observed reset voltage increased with temperature. To clarify the switching mechanism, conduction current fitting and switching voltage statistics were applied to explore the regular voltage variation dependent on temperature. In addition, a reaction model was proposed to explain the oxygen concentration gradient induced between the inserted SiO2 and ITO electrode on the ITO-based RRAM device.

A universal model for interface-type threshold switching phenomena by comprehensive study of Vanadium oxide-based selector

For the first time, a comprehensive study of Vanadium oxide-based selector characteristics with a universal model observed by thermal and electrical induced threshold switching (TS) phenomena at interface is presented in this work. The model can explain that the resistance evolution by thermal temperature in TS behaviors, as well as the resistance gradually increases with cycling (“seasoning effect”). Compatible current density (107∼109 A/cm2) and selectivity (∼100) with physical understanding of evolution in energy barrier and MIT metallic state modulation are studied. The results show a promising design guideline for future storage-class memory (SCM) applications.

Conduction Mechanism and Improved Endurance in HfO2-Based RRAM with Nitridation Treatment

A nitridation treatment technology with a urea/ammonia complex nitrogen source improved resistive switching property in HfO2-based resistive random access memory (RRAM). The nitridation treatment produced a high performance and reliable device which results in superior endurance (more than 109 cycles) and a self-compliance effect. Thus, the current conduction mechanism changed due to defect passivation by nitrogen atoms in the HfO2 thin film. At a high resistance state (HRS), it transferred to Schottky emission from Poole-Frenkel in HfO2-based RRAM. At low resistance state (LRS), the current conduction mechanism was space charge limited current (SCLC) after the nitridation treatment, which suggests that the nitrogen atoms form Hf–N–Ox vacancy clusters (Vo+) which limit electron movement through the switching layer.

Obtaining Lower Forming Voltage and Self-Compliance Current by Using a Nitride Gas/Indium–Tin Oxide Insulator in Resistive Random Access Memory

This paper investigates the characteristics of applying indium-tin oxide (ITO) with and without nitride gas (N2) as the insulator in resistive random access memory (RRAM). After cosputtering an ITO target with N2 as the insulator and capping the same ITO material as the top electrode, the device exhibits rectifier and resistance switching characteristics before and after the forming process, respectively. The Schottky diodelike rectifier mechanism was also verified by various temperature measurements. Furthermore, robust resistance switching at a positive forming voltage, smaller than that required during negative bias forming, can be achieved. Both positive and negative forming processes are examined with current fitting results, which show different dominant mechanisms when using positive or negative biases. All these mechanisms have also been verified by temperature effect experiments, which confirmed the dominant conduction mechanisms. This, in combination with the fact that the positive forming voltage itself is smaller than the negative forming voltage, and decreases with device scale down, provides two highly beneficial results. This good performance achieved by using ITO with N2 suggests significant progress of RRAM and remarkable potential applications.