Browsing by Author "Ma, Xiao-Hua"

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A characteristic improved technique and analysis with plasma treatment to the electrode on oxide-based resistive random access memory
(2020-03-15)
Lin, Chih-Yang
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Chang, Ting-Chang
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Pan, Chih-Hung
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Chen, Min-Chen
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Xu, You-Lin
A technique was proposed to concentrate the distribution of set voltages. After a plasma treatment, the stability of the high-resistive state (HRS) increased, and the distribution of set voltages was more concentrated at 0.8 V, with a sufficient HRS/LRS resistive ratio (similar to 100x). In addition, the surface of the TiN electrode became rougher, causing oxygen to enter the TiN electrode and form a TiON layer, which acts as an oxygen reservoir. The reservoir is confirmed and the conduction model is supported by both electrical and material analyses. We propose that the observed improvement is due to the difference in the TiN electrode surface. (C) 2019 Published by Elsevier B.V.
Enhanced electrical behavior from the galvanic effect in Ag-Cu alloy electrode conductive bridging resistive switching memory
(2018-07-30)
Tseng, Yi-Ting
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Chen, I-Chieh
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Chang, Ting-Chang
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Huang, J. C.
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Shih, Chih-Cheng
In this study, an Ag-Cu alloy was chosen as the electrode in conductive bridging random access memory (CBRAM), with results indicating a significant decrease in forming voltage. In addition, resistive switching characteristics as well as a retention test indicated better stability and a resistive switching window of at least an order, The switching time of the Ag-Cu alloy CBRAM is shorter than that of both Ag and Cu electrode CBRAMs under fast current-voltage (fast I-V). The experimental result indicated that the mechanism was dominated by the galvanic effect. Active atoms (Ag) captured electrons of inactive atoms (Cu) and generated metallic ions (Cu ions) in the alloy electrode, Cu ions drifted into the insulator and generated a conductive path when applying voltage bias, The use of this alloy as an electrode in CBRAM can significantly decrease forming voltage and enhance CBRAM characteristics. Published by AIP Publishing.
Enhancement of Surface Chemical and Physical Properties of Germanium-Sulfur Thin Film Using a Water-Supplemented Carbon Dioxide Supercritical Fluid Treatment Technique
(2018-11-09)
Yang, Chih-Cheng
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Chen, Po-Hsun
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Shih, Chih-Cheng
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Wang, Ming-Hui
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Tsai, Tsung-Ming
In this study, an oxidation treatment technique suitable for the material and electronic device applications proceeding at low temperature (only 80 degrees C) and high pressure (3000 psi) utilizing a carbon dioxide (CO2) supercritical fluid (SCF), also known as scCO(2), which is supplemented with water molecules, is reported. To demonstrate the possible effects on material and devices for the proposed SCF treatment, an amorphous germanium-sulfur (GeS) thin film and a GeS-based resistance random access memory (RRAM) device are prepared. After the SCF treatment, electrical measurements confirm that the GeS-based RRAM device exhibits a lower forming voltage, more stable resistance switching characteristics, and higher concentration distributions of high and low resistance states when compared to the device without SCF treatment. As for the material effects, both chemical and physical properties are examined based on material analyses results. It is concluded that the original amorphous GeS thin film transforms to a polycrystallized GeO film, confirmed by a reaction model for the SCF treatment illustrating possible oxidation and crystallization effects induced by this SCF treatment. This water-enhanced scCO(2) SCF treatment technique, thus, shows its capability as a feasible synthetic method for material modification as well as suitability for device level applications.
Improvement of Resistive Switching Characteristics in Zinc Oxide-Based Resistive Random Access Memory by Ammoniation Annealing
(2020-03-01)
Wu, Pei-Yu
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Zheng, Hao-Xuan
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Shih, Chih-Cheng
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Chang, Ting-Chang
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Chen, Wei-Jang
In this experiment, the electrical performance of zinc oxide based-resistive random access memory (RRAM) is successfully improved by using annealing in ammonia hydroxide solution at low-temperature and high pressure to complete ammonium-doped ZnO based-RRAM. The results of material analysis indicate that using CO2 as ammonia hydroxide carrier during the annealing process leads to the reduction in dangling bond density. This can be clearly observed in the decrease in breakdown voltage during the forming process and a lower operating current during operation. Furthermore, in this ammonium-doped ZnO based-RRAM, we study the molecular doping of NH3 in ZnO, where the endurance and retention properties are improved as well. These improvements can be attributed to the higher concentration of nitrogen in the switching layer, which can effectively control the active oxygen ions during the operation process.
Investigating Material Changes at Different Gadolinium Doping Power Levels in Indium-Tin Oxide Intended for Use as an Insulator in Resistive Switching Memory
(2019-06-01)
Lin, Chun-Chu
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Chen, Po-Hsun
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Chen, Min-Chen
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Chang, Ting-Chang
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Lin, Chih-Yang
This paper investigates material modifications induced by cosputtering indium-tin oxide (ITO) with gadolinium (Gd) at two different power levels. In addition, resistance switching (RS) properties were also verified for use as an insulator in resistive random access memory (RRAM). Comparison of scanning electron microscope (SEM) measurements for the two different cosputtering powers indicated significant changes of the ITO surface. Transparency was also verified by an N&K analyzer measurement, with results indicating a constant in transparency induced by the lower power Gd doping, indicating potential for transparent applications. Furthermore, the mole fraction ratio defined by X-ray photoelectron spectroscopy reveals a Gd2O3 peak, a likely reason for the ITO thin film becoming less conductive. This ITO/Gd:ITO/TiN RRAM can exhibit stable and robust RS characteristics at a lower forming voltage. In addition, lower operating voltages, including both SET and RESET voltages, can be obtained. Reliability tests including endurance and retention were carried out to confirm its RS stability. The RS mechanism of this ITO/Gd:ITO/TiN device was also investigated with the current-voltage (I-V) fitting method. Moreover, temperature effects were also applied to verify the high-resistance state (HRS) mechanism. Finally, a conduction model was proposed to clarify the RS characteristics and confirm that the ITO/Gd:ITO/TiN device is appropriate for data storage.
Investigation of the forming process under UV illumination in HfO2-based resistance random access memory with a transparent electrode
(2020-01-09)
Huang, Wei-Chen
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Huang, Shin-Ping
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Chen, Po-Hsun
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Chen, Min-Chen
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Chang, Ting-Chang
Traditionally, metal is used for the top electrode (TE) in HfO2-based resistance random access memory. When transparent indium-tin-oxide (ITO) is used as the TE, different forming processes, including lower forming voltages and higher forming currents, are exhibited. This work investigates the forming process with such a transparent TE under UV illumination. In addition, different TE thicknesses and device cell sizes are also investigated to confirm the results. Finally, a possible conduction model is provided to explain the mechanisms under UV-light illumination for the transparent TE during the forming process.
Overcoming Limited Resistance in 1T1R RRAM Caused by Pinch-Off Voltage During Reset Process
(2019-11-01)
Zheng, Hao-Xuan
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Chen, Min-Chen
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Chang, Ting-Chang
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Su, Yu-Ting
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Chen, Wen-Chung
This article explains the difference in the reset processes between single RRAM and 1T1R RRAM structures. In the single RRAM, as the reset voltage increases, the off-state resistance increases. This is a normal RRAM operation. However, in the 1T1R structure, the reset voltage increases while the OFF-state resistance does not increase. This may be caused by either current or voltage being insufficient to switch the RRAM to its higher resistance state. The measurements of real voltage indicate that the insufficient voltage is in fact the main cause. For the 1T1R RRAM structure, if it is to be reset to a higher resistance state, it is best done by increasing the gate voltage to increase the OFF-state resistance. Therefore, we provide a method to reduce the misjudgment in the array, and it would be beneficial for the development of high-density memory.
Performance improvement after nitridation treatment in HfO2-based resistance random-access memory
(2018-08-01)
Wang, Ming-Hui
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Chang, Ting-Chang
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Shih, Chih-Cheng
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Tseng, Yi-Ting
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Tsai, Tsung-Ming
Nitrogen atoms were introduced into a Pt/HfO2/TiN resistance random-access memory (RRAM) device to improve the resistive switching characteristics induced by a high-pressure nitridation treatment. Compared with a similar untreated HfO2 device, it exhibited superior performance, including a lower forming voltage, a higher on/off ratio, and high-endurance cycle operations. Current-voltage curve-fitting results confirmed the difference of the carrier transport mechanisms after the nitridation treatment. Finally, a reaction model was proposed to explain the improvement of RRAM switching due to the introduction of nitrogen atoms. (C) 2018 The Japan Society of Applied Physics
The influence of temperature on set voltage for different high resistance state in 1T1R devices
(2019-02-01)
Tan, Yung-Fang
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Su, Yu-Ting
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Chen, Min-Chen
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Chang, Ting-Chang
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Tsai, Tsung-Ming
HfO2-based 1T1R is researched in this paper. The on-off ratio is an important electrical characteristic of RRAM, with a larger on-off ratio being preferable. However, temperature also affects the set process when operating RRAM. This study finds that the set process has different sensitivities to temperature at different high resistance states (HRSs). The set voltage of the higher HRS decreases with increasing temperature, while in the lower HRS, set voltage is independent of temperature. From the result, the lower HRS is better for RRAM because it is stable at different temperatures. (C) 2019 The Japan Society of Applied Physics