Browsing by Author "Pan, Chih-Hung"

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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.
A Universal Model for Interface-type Threshold Switching Phenomena by Comprehensive Study of Vanadium Oxide-Based Selector
(2017-01-01)
Lin, Chih-Yang
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Chen, Ying-Chen
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Gu, Meiqi
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Pan, Chih-Hung
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Jin, Fu-Yuan
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 (10(7)similar to 10(9) A/cm(2)) and selectivity (similar to 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.
Adjustable built-in resistor on oxygen-vacancy-rich electrode-capped resistance random access memory
(2016-10)
Pan, Chih-Hung
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Chang, Ting-Chang
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Tsai, Tsung-Ming
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Chang, Kuan-Chang
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Chu, Tian-Jian
In this study, an adjustable built-in resistor was observed on an indium-tin oxide (ITO)-capped resistance random access memory (RRAM) device, which has the potential to reduce operating power. Quite notably, the high-resistance state (HRS) current of the device decreased with decreasing current compliance, and a special situation, that is, a gradual change in current always appears and climbs slowly to reach the compliance current in the set process even when the compliance current decreases, was observed. Owing to this observed phenomenon, the device is regarded to be equipped with an adjustable built-in resistor, which has the potential for low-power device application. (C) 2016 The Japan Society of Applied Physics
Analyzing Electric Field Effect by Applying an Ultra-Short Time Pulse Condition in Hafnium Oxide-Based RRAM
(2018-08-01)
Wu, Cheng-Hsien
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Lin, Shih-Kai
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Pan, Chih-Hung
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Chen, Po-Hsun
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Lin, Wen-Yan
In this letter, we determine the importance of the electrical field distribution and strength during the switching process by demonstrating different trends in the degree of reset and the reset pulse time. In general, a longer reset pulse time results in a higher reset energy; a higher reset energy leads to a higher degree of reset, which we obtainedby applying different width square waves. But quite notably, the opposite result was obtained using triangle waves, where a higher degree of reset occurred with a shorter rising time and lower reset energy. We believe that this is due to the electric field effect: if the voltage rises faster than the filament oxidation, the device can produce a larger effective electric field and a higher resistance in the reset process. To further investigate the mechanism, the procedure of the reset process was analyzed in detail, and COMSOL simulation is also carried out for confirmation.
Attaining resistive switching characteristics and selector properties by varying forming polarities in a single HfO2-based RRAM device with a vanadium electrode
(2017-07-07)
Lin, Chih-Yang
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Chen, Po-Hsun
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Chang, Ting-Chang
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Chang, Kuan-Chang
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Zhang, Sheng-Dong
This study proposes a method for a HfO2-based device to exhibit both resistive switching (RS) characteristics as resistive random access memory (RRAM) and selector characteristics by introducing vanadium (V) as the top electrode. This simple V/HfO2/TiN structure can demonstrate these two different properties depending on forming polarities. The RS mechanism is activated by a positive forming bias. In contrast, the selector property is induced by a negative forming bias. The material analyses firstly confirm the existence of V in the top electrode. Then the electrical measurements for the same V/HfO2/TiN structures but with different forming polarities were carried out to further investigate their DC sweeping characteristics to act as either a selector or RRAM device. Furthermore, reliability tests for both selector and RRAM devices were also conducted to confirm their switching stabilities. Finally, current fitting methods and temperature influence experiments were performed to investigate the carrier transport mechanisms. Finally, physical models were proposed to illustrate the selector property and RS mechanism for selector and RRAM devices, respectively. This simple device structure with its easy operating method accomplishes a significant advancement of devices combining both selector properties and RRAM for remarkable real applications in the near future.
Characteristics of hafnium oxide resistance random access memory with different setting compliance current
(2013-10-14)
Su, Yu-Ting
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Chang, Kuan-Chang
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Chang, Ting-Chang
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Tsai, Tsung-Ming
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Zhang, Rui
In this Letter, the characteristics of set process of hafnium oxide based resistance random access memory are investigated by different set processes with increasing compliance current. Through current fitting, carrier conduction mechanism of low resistance state changes from hopping to surface scattering and finally to ohmic conduction with the increase of setting compliance current. Experimental data of current-voltage measurement under successive increasing temperature confirms the conduction mechanism transition. A model of filament growth is eventually proposed in a way by merging discrete metal precipitates and electrical field simulation by COMSOL Multiphysics further clarifies the properties of filament growth process. (C) 2013 AIP Publishing LLC.
Confirmation of filament dissolution behavior by analyzing electrical field effect during reset process in oxide-based RRAM
(2016-09-26)
Pan, Chih-Hung
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Chang, Ting-Chang
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Tsai, Tsung-Ming
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Chang, Kuan-Chang
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Chu, Tian-Jian
In this letter, we demonstrate completely different characteristics with different operating modes and analyze the electrical field effect to confirm the filament dissolution behavior. The device exhibited a larger memory window when using a single voltage sweep method during reset process rather than the traditional double sweep method. The phenomenon was verified by using fast I-V measurement to simulate the two operating methods. A better high resistance state (HRS) will be obtained with a very short rising time pulse, but quite notably, lower power consumption was needed. We proposed the electrical field effect to explain the phenomenon and demonstrate distribution by COMSOL simulation. Published by AIP Publishing.
Effect of charge quantity on conduction mechanism of high-and low-resistance states during forming process in a one-transistor-one-resistor resistance random access memory
(2017-05-01)
Wu, Cheng-Hsien
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Chang, Ting-Chang
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Tsai, Tsung-Ming
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Chang, Kuan-Chang
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Chu, Tian-Jian
The forming process is a necessary and irreversible process to activate the resistance switching behavior in a resistance random access memory (RRAM) device. However, during the forming process, an overshoot current leads to device damage and causes inferior resistance switching characteristics; consequently, the process is considered to be a key factor in device degradation. In this paper, we find that a discontinuous conduction path can be formed by a pulse forming process such that the operation current can be reduced. We further investigate how the charge quantity during the forming process affects the carrier conduction mechanism of HRS, with all experiments and results demonstrated on onetransistor- one-resistor (1T1R) devices. (C) 2017 The Japan Society of Applied Physics
Effects of erbium doping of indium tin oxide electrode in resistive random access memory
(2016-03)
Chen, Po-Hsun
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Chang, Kuan-Chang
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Chang, Ting-Chang
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Tsai, Tsung-Ming
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Pan, Chih-Hung
Identical insulators and bottom electrodes were fabricated and capped by an indium tin oxide (ITO) film, either undoped or doped with erbium (Er), as a top electrode. This distinctive top electrode dramatically altered the resistive random access memory (RRAM) characteristics, for example, lowering the operation current and enlarging the memory window. In addition, the RESET voltage increased, whereas the SET voltage remained almost the same. A conduction model of Er-doped ITO is proposed through current-voltage (I-V) measurement and current fitting to explain the resistance switching mechanism of Er-doped ITO RRAM and is confirmed by material analysis and reliability tests. (C) 2016 The Japan Society of Applied Physics
Effects of Varied Negative Stop Voltages on Current Self-Compliance in Indium Tin Oxide Resistance Random Access Memory
(2015-06-01)
Lin, Chih-Yang
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Chang, Kuan-Chang
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Chang, Ting-Chang
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Tsai, Tsung-Ming
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Pan, Chih-Hung
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.
Endurance Improvement Technology With Nitrogen Implanted in the Interface of WSiOx Resistance Switching Device
(2013-07-01)
Syu, Yong-En
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Zhang, Rui
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Chang, Ting-Chang
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Tsai, Tsung-Ming
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Chang, Kuan-Chang
Incorporation of nitrogen as an oxygen-confining layer in the resistance switching reaction region is investigated to improve the reliability of resistance random access memory (RRAM). The switching mechanism can be attributed to the formation and rupture of conduction filaments. A compatible WSiON (around 5 nm) layer is introduced at the interface of tungsten silicon oxide (WSiOx) and TiN electrode to prevent the randomly diffusing oxygen ions surpassing the storage region of the WSiON layer. The double-layer WSiOx/WSiON memory structure would enhance the endurance over 100 times so as to better confirm the WSiOx RRAM application of nonvolatile memory.
Engineering interface-type resistance switching based on forming current compliance in ITO/Ga2O3: ITO/TiN resistance random access memory: Conduction mechanisms, temperature effects, and electrode influence
(2016-10-31)
Pan, Chih-Hung
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Chang, Ting-Chang
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Tsai, Tsung-Ming
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Chang, Kuan-Chang
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Chen, Po-Hsun
In this paper, an ITO/Ga2O3: ITO/TiN structured resistance random access memory is introduced. Either interface or filament conduction mechanism can be induced depending on the forming compliance current, which has not been investigated before. Material analyses and electrical I-V measurements on this ITO/Ga2O3: ITO/TiN have also been carried out. The interface conduction mechanism was confirmed by a size-effect experiment, where resistance varied inversely to via size. In addition, the current fitting results show that Schottky emission dominates the on-and off-state currents. All physical mechanisms of device resistive switching behaviors are explained by our models and also confirmed by I-V characteristics. Published by AIP Publishing.
High performance of graphene oxide-doped silicon oxide-based resistance random access memory
(2013-11-21)
Zhang, Rui
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Chang, Kuan-Chang
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Chang, Ting-Chang
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Tsai, Tsung-Ming
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Chen, Kai-Huang
In this letter, a double active layer (Zr:SiO (x) /C:SiO (x) ) resistive switching memory device with outstanding performance is presented. Through current fitting, hopping conduction mechanism is found in both high-resistance state (HRS) and low-resistance state (LRS) of double active layer RRAM devices. By analyzing Raman and FTIR spectra, we observed that graphene oxide exists in C:SiO (x) layer. Compared with single Zr:SiO (x) layer structure, Zr:SiO (x) /C:SiO (x) structure has superior performance, including low operating current, improved uniformity in both set and reset processes, and satisfactory endurance characteristics, all of which are attributed to the double-layer structure and the existence of graphene oxide flakes formed by the sputter process.
Hopping Effect of Hydrogen-Doped Silicon Oxide Insert RRAM by Supercritical CO2 Fluid Treatment
(2013-05-01)
Chang, Kuan-Chang
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Pan, Chih-Hung
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Chang, Ting-Chang
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Tsai, Tsung-Ming
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Zhang, Rui
In this letter, we introduced hydrogen ions into titanium metal doped into SiO2 thin film as the insulator of resistive random access memory (RRAM) by supercritical carbon dioxide (SCCO)(2) fluid treatment. After treatment, low resistance state split in to two states, we find the insert RRAM, which means it has an operating polarity opposite from normal RRAM. The difference of the insert RRAM is owing to the resistive switching dominated by hydrogen ions, dissociated from OH bond, which was not by oxygen ions as usual. The current conduction mechanism of insert RRAM was hopping conduction due to the metal titanium reduction reaction through SCCO2.
Identical Off-state Current Raise Induced by Photo-induced Schottky Barrier Lowering in a-InGaZnO4 Thin Film Transistors
(2016)
Chen, Hua-Mao
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Chang, Ting-Chang
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Liao, Po-Yung
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Chiang, Hsiao-Cheng
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Chen, Ching-En
This work studies the mechanism of identical photoinduced leakage current in a-InGaZnO4 thin film transistors during reverse gate voltage sweep. There is the identical off-state current with the reverse sweep under UV light irradiation, and the photocurrent for UV light exposure region near the source electrode is more significant than that near the drain electrode, which is different from photocurrent mechanism of low temperature polysilicon TFTs. This is because the photo-generated electrons increase the carrier concentration in a-InGaZnO4 bulk, causing the reduced depletion width of the active layer. Therefore, the back channel of active layer is out of gate control.
Improving Performance by Doping Gadolinium Into the Indium-Tin-Oxide Electrode in HfO2-Based Resistive Random Access Memory
(2016-05)
Chen, Po-Hsun
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Chang, Kuan-Chang
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Chang, Ting-Chang
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Tsai, Tsung-Ming
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Pan, Chih-Hung
This letter investigates the characteristics of doping gadolinium (Gd) in an indium-tin-oxide (ITO) electrode in HfO2-based resistive random access memory (RRAM). Identical bottom electrodes and insulators were made but then capped by either pure ITO or a Gd: ITO top electrode. Doping Gd in the ITO electrode produces lower operation currents in both high-resistance state (HRS) and low-resistance state (LRS) as well as enlarging the memory window. This excellent performance suggests a remarkable potential to improve RRAM applications. Schottky emission mechanism dominates both HRS and LRS according to current fitting results, and is confirmed by temperature effect experiments. The resistive switching behavior of the Gd:ITO device is explained by our model and is also confirmed by material analysis and electrical measurements. Furthermore, reliability tests verify the Gd: ITO device\'s capability to perform data storage as a nonvolatile memory.
Inert Pt electrode switching mechanism after controlled polarity-forming process in In2O3-based resistive random access memory
(2017-09-01)
Wu, Cheng-Hsien
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Pan, Chih-Hung
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Chen, Po-Hsun
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Chang, Ting-Chang
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Tsai, Tsung-Ming
In this study, we demonstrate a forming technique that enables us to control whether the switching layer of a Pt/In2O3/TiN device is near the Pt electrode or the TiN electrode. This means that In2O3-based resistive random access memory (RRAM) can be switched at either the active or inert electrode. The resistive switching current-voltage (I-V) curves for both electrodes exhibit stable memory windows. Through material and electrical analyses, we found that the reason for switching at the inert electrode is the oxygen-vacancy-rich characteristic of In2O3. Finally, a physical model is proposed to explain this phenomenon. (C) 2017 The Japan Society of Applied Physics
Investigation of Abnormal Off-Current in p-Channel Double Diffused Drain Metal-Oxide-Semiconductor Transistors after Hot Carrier Stress
(2016)
Chen, Ching-En
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Chang, Ting-Chang
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Lu, Ying-Hsin
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Chen, Hua-Mao
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Chen, Bo-Wei
This paper studies the degradation behaviors in IV characteristics and the corresponding improvement for p-channel double diffused drain metal-oxide-semiconductor (DDDMOS) transistors after hot carrier stress (HCS). There is an apparent current which is flowed from source to drain in the off-region after HCS. According to the IV characteristic comparisons between different device structures and ISE-TCAD simulation results, the location and mechanism of this abnormal off-current can be demonstrated. Furthermore, this off-current is suppressed effectively by the different process flows in STI fabrication for this DDDMOS device.
Low Temperature Improvement Method on Zn:SiOx Resistive Random Access Memory Devices
(2013-04-01)
Chang, Kuan-Chang
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Tsai, Tsung-Ming
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Chang, Ting-Chang
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Wu, Hsing-Hua
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Chen, Kai-Huang
To improve the resistive switching properties of the resistive random access memory (RRAM), the supercritical carbon dioxide (SCCO2) fluid is used as a low temperature treatment. In this letter, the Zn:SiOx thin films are treated by SCCO2 fluid mixed with pure water. After SCCO2 fluid treatment, the resistive switching qualities of the Zn:SiOx thin films are carried out by XPS, fourier transform infrared spectroscopy, and IV measurement. We believe that the SCCO2-treated Zn:SiOx thin film is a promising material for RRAM applications due to its compatibility with portable flat panel display.
Modifying Indium-Tin-Oxide by Gas Cosputtering for Use as an Insulator in Resistive Random Access Memory
(2016-11)
Chen, Po-Hsun
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Chang, Kuan-Chang
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Chang, Ting-Chang
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Tsai, Tsung-Ming
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Pan, Chih-Hung
In this paper, indium-tin-oxide (ITO) was used to act as both insulator and top electrode in resistive random access memory (RRAM) on identical bottom substrates. This is achieved by cosputtering an ITO target with nitride (N-2) or oxygen (O-2) gas as the insulator; then capping by an ITO electrode, such that both the rectifier and RRAM characteristics can be achieved before and after a forming process, respectively. In contrast, using pure ITO as an insulator does not exhibit RRAM behavior. To verify the rectifier and RRAM characteristics, material analyses and electrical measurements at various temperatures were conducted. Reliability tests including retention and endurance were also applied to verify the resistance switching stability. Finally, the rectifier and RRAM conduction models were proposed to examine the resistance switching behaviors. By applying the ITO material as both electrode and insulator, the resistance switching characteristic with high reliability is thus obtained.