Browsing by Author "Chen, Shih-Cheng"

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Bipolar resistive switching of chromium oxide for resistive random access memory
(2011-08-01)
Chen, Shih-Cheng
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Chang, Ting-Chang
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Chen, Shih-Yang
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Chen, Chi-Wen
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Chen, Shih-Ching
This study investigates the resistance switching characteristics of Cr(2)O(3)-based resistance random access memory (RRAM) with Pt/Cr(2)O(3)/TiN and Pt/Cr(2)O(3)/Pt structures. Only devices with Pt/Cr(2)O(3)/TiN structure exhibit bipolar switching behavior after the forming process because TiN was able to work as an effective oxygen reservoir but Pt was not. Oxygen migration between Cr(2)O(3) and TiN was observed clearly before and after resistance switching from Auger electron spectroscopy (AES) analysis. Both low resistance state, ON state, and high resistance state, OFF state, of Pt/Cr(2)O(3)/TiN structures are stable and reproducible during a successive resistive switching. The resistance ratio of ON and OFF state is over 10(2), on top of that, the retention properties of both states are very stable after 10(4) s with a voltage of -0.2 V. (C) 2010 Elsevier Ltd. All rights reserved.
Carrier Transport and Multilevel Switching Mechanism for Chromium Oxide Resistive Random-Access Memory
(2011)
Chen, Shih-Cheng
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Chang, Ting-Chang
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Chen, Shih-Yang
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Li, Hung-Wei
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Tsai, Yu-Ting
This article investigates the carrier transport phenomenon and multilevel switching mechanism of Cr(2)O(3)-based resistive random access memory (RRAM) with Pt/Cr(2)O(3)/TiN structure. Before the forming process, the interfacial Schottky barrier dominates the carrier transport. The barrier heights of Pt/Cr(2)O(3) and Cr(2)O(3)/TiN are 0.7 and 0.96 eV, respectively. After the forming process, RRAM at a low resistance state follows the Ohmic conduction. While RRAM is switched to a high resistance state during the reset process, the Frenkel-Poole emission becomes a dominant conduction mechanism. The multilevel resistance states were achieved by applying corresponding reset voltages to the device for controlling the trap levels of the Cr(2)O(3) layer. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3518710] All rights reserved.
Characteristics of poly-Si TFT combined with nonvolatile SONOS memory and nanowire channels structure
(2007-12-15)
Chen, Shih-Ching
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Chang, Ting-Chang
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Liu, Po-Tsun
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Wu, Yung-Chun
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Lin, Po-Shun
In this work, we study a polycrystalline silicon thin-film transistor (poly-Si TFT) combined with a silicon-oxide-nitride-oxide-silicon (SONOS) stack gate dielectric and nanowire channels structure for the applications of transistor and nonvolatile memory. The proposed device named with NW SONOS-TFT has superior electrical characteristics of transistor and also can exhibit high program/erase (P/E) efficiency under adequate bias operation. The V-th decreases from 2.45 V to 1.76 V and subthreshold swing reduces from 0.57 V/decade to 0.42 V/decade. The programming V-th shift is improved from 2.2 V to 3.3 V at 14 V for 1 s and the erasing V-th shift is improved from -0.3 V to -1.3 V at -14 V for 1 s. The dramatic improvement can be attributed to the tri-gate structure and corner effect. In addition, the memory device has a promising data retention behavior at 85 degrees C and a 0.8 V memory window after 5 x 10(3) P/E cycles operations. Hence, the NW SONOS-TFT is suitable for application in the future system-on-panel display. (C) 2007 Elsevier B.V. All rights reserved.
Characterization of environment-dependent hysteresis in indium gallium zinc oxide thin film transistors
(2013-09-01)
Chen, Yu-Chun
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Chang, Ting-Chang
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Li, Hung-Wei
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Chung, Wan-Fang
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Chen, Shih-Cheng
This study investigates environmentally dependent electrical performance as a function of hysteresis phenomena for amorphous indium-gallium-zinc-oxide (a-IGZO) thin film transistors (TFTs). Because ambient gas has a great influence on the electrical characteristics of zinc oxide-based TFTs during electrical measurements, the hysteresis for current-voltage and capacitance-voltage measurements are employed in different ambient gases (ambient air, vacuum, oxygen ambient and moisture ambient) to study this issue. Although the hysteresis phenomenon has been explained by the charge trapping and de-trapping model, in order to obtain stable electrical characteristics it is necessary to clarify the original principal mechanism leading to threshold voltage instability under gate bias operations in different environments. Also, the relationship between de-trapping rate and electrical hysteresis is investigated by prolonging the integration time of the semiconductor parameter analyzer. This study may be of importance in explaining the dynamic relationship between the TFT electrical characteristics and ambient gas, as well as providing a better understanding of the environment-dependent hysteresis phenomenon of the IGZO TFTs. (C) 2012 Elsevier B.V. All rights reserved.
Developments in nanocrystal memory
(2011-12-01)
Chang, Ting-Chang
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Jian, Fu-Yen
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Chen, Shih-Cheng
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Tsai, Yu-Ting
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電子工程學系及電子研究所
Since the 1990s, portable electronic products have been a prominent part of our daily lives; and many of these devices require flash memories. The floating-gate (FG) structure, invented by Sze and Kahng at Bell Labs in 1967, forms the primary technology necessary to construct flash memories(1), Fig. 1a. In order to meet the demands of product miniaturization, the shrinking of transistors has evolved as a method to not only pack more devices into a given area, but also improve the switching speed. In such a situation, conventional nonvolatile memory (FG) suffers from certain physical limitations, such as an insufficient tunneling oxide thickness from the continual scaling down of the device structures(2). Because the floating gate (as a charge storing layer) is conductive, all charge will be lost if a leakage path appears in the tunneling oxide, resulting in a serious reliability issue for memory applications. Discrete nanocrystal memory was first proposed by IBM in 1995, and by the early 2000s researchers were already considering it to be a promising candidate for the solution of the scaling problem(3) (Fig. 1b). In addition, nanocrystal memory has a two bit per cell storage capability due to its discrete electron storing center. This means that more data can be stored in one memory cell, which readily increases the memory density(4).
Effect of Electrode Material on Resistive Switching Characteristics in TaON Nonvolatile Memory Devices
(2013-01-01)
Chen, Min-Chen
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Chang, Ting-Chang
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Chiu, Yi-Chieh
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Chen, Shih-Cheng
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Huang, Sheng-Yao
The devices composed of Pt/TaON/TiN reveal bipolar switching behavior that shows excellent resistance ratio of 10(2) with operations over 100 DC cycles. The formation/disruption of conducting filaments by oxygen anions migration near/at the TiN electrode was applied to explain the switching behavior. In comparison with Pt/TaON/TiN device, the Cu/TaON/TiN device exhibits reversed bipolar resistive switching characteristic. The switching mechanism of Cu/TaON/TiN device is regarded as the Cu redox reaction and migration in the TaON film. Furthermore, the setting voltage of the Cu/TaON/TiN device is lower than that of the Pt/TaON/TiN device due to the confined conduction path by Cu filaments.
Effect of Top Electrode Material on Resistive Switching Characteristics in MnO2 Nonvolatile Memory Devices
(2011)
Tsai, Yu-Ting
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Chang, Ting-Chang
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Lin, Chao-Cheng
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Chiang, Lan-Shin
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Chen, Shih-Cheng
The influence of top electrode material on the resistive switching properties of MnO2-based memory film using Pt as a bottom electrode was investigated in this study. In comparison with Pt/MnO2/Pt and Al/ MnO2/Pt devices, the Ti/ MnO2/Pt device exhibits resistive switching current-voltage (I-V) curve, which can be traced and reproduced more than 10(5) times only showing a little decrease of resistance ratio between high and low resistance states. Furthermore, transmission electron microscopy analyses are used to confirm the crystalline structure of MnO2 on Pt bottom electrode. Secondary ion mass spectrometry reveals a change of oxygen distribution in MnO2 thin film due to material characteristic of variant top electrodes. We suggest that the interface between MnO2 and electrodes play an important role on the resistive switching behaviors.
Formation and composition of titanium oxinitride nanocrystals synthesized via nitridizing titanium oxide for nonvolatile memory applications
(2011-09-01)
Feng, Li-Wei
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Chang, Chun-Yen
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Chang, Ting-Chang
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Tu, Chun-Hao
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Wang, Pai-Syuan
Formation and composition analyses of titanium oxinitride nanocrystals (NCs) fabricated via treating a magnetron co-sputtered thin film of titanium and silicon dioxide with a rapid thermal annealing in nitrogen ambient were demonstrated for nonvolatile memory applications. Phase separation characteristics with different annealing conditions were examined by transmission electron microscopy and chemical bonding characteristics were confirmed by X-ray photon emission spectra. It was observed that a blanket layer composed mainly of titanium oxide was still present as annealing temperature was increased to 700 degrees C, associated with the thermodynamically stable phase of titanium oxide. Furthermore, a higher thermal treatment of 900 degrees C induced formation of a well-separated NC structure and caused simultaneously partial nitridation of the titanium oxide, thereby forming titanium oxinitride NCs. A significant capacitance-voltage hysteresis in threshold voltage shift at 1 V was easily achieved under a small sweeping voltage range of + 2 V/-2 V, and a memory window retention of 2.2 V was obtained after 10(7) s by extrapolation under a 1 s initial-program/erase condition of +5 V/-5 V, respectively. (C) 2011 Elsevier B.V. All rights reserved.
Formation and nonvolatile memory characteristics of W nanocrystals by in-situ steam generation oxidation
(2010-12-30)
Chen, Shih-Cheng
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Chang, Ting-Chang
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Hsieh, Chieh-Ming
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Li, Hung-Wei
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Sze, S. M.
The authors provide the formation and memory effects of W nanocrystals nonvolatile memory in this study. The charge trapping layer of stacked a-Si and WSi(2) was deposited by low pressure chemical vapor deposition (LPCVD) and was oxidized by in-situ steam generation system to form uniform W nanocrystals embedded in SiO(2). Transmission electron microscopy analyses revealed the microstructure in the thin film and X-ray photon-emission spectra indicated the variation of chemical composition under different oxidizing conditions. Electrical measurement analyses showed the different charge storage effects because the different oxidizing conditions influence composition of trapping layer and surrounding oxide quality. Moreover, the data retention and endurance characteristics of the formed W nanocrystal memory devices were compared and studied. The results show that the reliability of the structure with 2% hydrogen and 98% oxygen at 950 degrees C oxidizing condition has the best performance among the samples. (C) 2010 Elsevier B.V. All rights reserved.
Improvement of resistance switching characteristics in a thin FeO(x) transition layer of TiN/SiO(2)/FeO(x)/FePt structure by rapid annealing
(2010-05-31)
Feng, Li-Wei
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Chang, Chun-Yen
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Chang, Yao-Feng
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Chang, Ting-Chang
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Wang, Shin-Yuan
In this paper, the influence of a 600 degrees C rapid thermal annealing for 60 s on the improvements of resistance switching behaviors in a TiN/SiO(2)/FeO(x)/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/SiO(2)/FeO(x)/FePt resistance switching memory. (C) 2010 American Institute of Physics. [doi:10.1063/1.3428777]
Improvement of resistance switching characteristics in a thin FeOx transition layer of TiN/SiO2/FeOx/FePt structure by rapid annealing
(2010-05-31)
Feng, Li-Wei
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Chang, Chun-Yen
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Chang, Yao-Feng
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Chang, Ting-Chang
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Wang, Shin-Yuan
In this paper, the influence of a 600 degrees 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. (C) 2010 American Institute of Physics. [doi:10.1063/1.3428777]
Influence of hydrogen plasma treatment on charge storage characteristics in high density tungsten nanocrystal nonvolatile memory
(2011-03-31)
Chen, Shih-Cheng
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Chang, Ting-Chang
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Chen, Wei-Ren
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Lo, Yuan-Chun
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Wu, Kai-Ting
This study focuses on the influence of a hydrogen plasma treatment on electrical properties of tungsten nanocrystal nonvolatile memory. The X-ray photon emission spectra show that, after the hydrogen plasma treatment, a change in binding energy occurs such that Si(x+) and Si(y+) peaks appear at a position that is shifted about 2.3 and 3.3 eV from Si(o+) in Si 2p spectra. This indicates that Si dangling bonds are passivated to form a Si-H bond structure in the SiO(2). Furthermore, the transmission electron microscopy shows cross-sectional and plane-view for the nanocrystal microstructure after the hydrogen plasma treatment. Electrical measurement analyses show improved data retention because the hydrogen plasma treatment enhances the quality of the oxide surrounding the nanocrystals. The endurance and retention properties of the memory device are improved by about 36% and 30%, respectively. (C) 2011 Elsevier By. All rights reserved.
Influence of Nanocrystals on Resistive Switching Characteristic in Binary Metal Oxides Memory Devices
(2011)
Tsai, Yu-Ting
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Chang, Ting-Chang
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Lin, Chao-Cheng
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Chen, Shih-Cheng
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Chen, Chi-Wen
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. (C) 2010 The Electrochemical Society. [DOI: 10.1149/1.3531843] All rights reserved.
Influence of Oxygen Partial Pressure on Resistance Random Access Memory Characteristics of Indium Gallium Zinc Oxide
(2011)
Chen, Min-Chen
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Chang, Ting-Chang
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Huang, Sheng-Yao
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Chang, Guan-Chang
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Chen, Shih-Cheng
This paper investigates the effect of oxygen concentrations of InGaZnO films on the resistive switching characteristics of a Pt/InGaZnO (IGZO)/TiN structure. The IGZO films were prepared by an RF magnetron sputtering system at various oxygen partial pressures at room temperature. The memory devices reveal a reversible unipolar switching behavior. In addition, the high-resistance state current was found to be strongly dependent on oxygen concentration. X-ray photoelectron spectroscopy analyses attributed this phenomenon to the non-lattice oxygen concentration in the IGZO thin films, rather than the change in crystalline constituent. (C) 2011 The Electrochemical Society. [DOI: 10.1149/2.007112esl] All rights reserved.
Investigation for coexistence of dual resistive switching characteristics in DyMn(2)O(5) memory devices
(2011-08-29)
Tsai, Yu-Ting
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Chang, Ting-Chang
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Huang, Wei-Li
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Huang, Chih-Wen
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Syu, Yong-En
Dual bipolar resistive switching characteristics were observed in the Pt/DyMn(2)O(5)/TiN memory devices. The typical switching effect could be attributed to the formation and rupture of the conducting filament in DyMn(2)O(5) films. The parasitic switching behavior can be observed in the specific operation condition. Dual bipolar resistance switching behaviors of filament-type and interface-type can coexist in the devices by appropriate voltage operation. The operating current can be significantly decreased (100 times) by parasitic switching operation for portable electronic product application. In addition, the relationship between filament-type and interface-type switching behaviors were studied in this paper. (C) 2011 American Institute of Physics. [doi:10.1063/1.3629788]
Investigation for coexistence of dual resistive switching characteristics in DyMn2O5 memory devices
(2011-08-29)
Tsai, Yu-Ting
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Chang, Ting-Chang
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Huang, Wei-Li
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Huang, Chih-Wen
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Syu, Yong-En
Dual bipolar resistive switching characteristics were observed in the Pt/DyMn2O5/TiN memory devices. The typical switching effect could be attributed to the formation and rupture of the conducting filament in DyMn2O5 films. The parasitic switching behavior can be observed in the specific operation condition. Dual bipolar resistance switching behaviors of filament-type and interface-type can coexist in the devices by appropriate voltage operation. The operating current can be significantly decreased (100 times) by parasitic switching operation for portable electronic product application. In addition, the relationship between filament-type and interface-type switching behaviors were studied in this paper. (C) 2011 American Institute of Physics. [doi:10.1063/1.3629788]
Low temperature synthesis and electrical characterization of germanium doped Ti-based nanocrystals for nonvolatile memory
(2011-11-30)
Feng, Li-Wei
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Chang, Chun-Yen
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Chang, Ting-Chang
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Tu, Chun-Hao
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Wang, Pai-Syuan
Chemical and electrical characteristics of Ti-based nanocrystals containing germanium, fabricated by annealing the co-sputtered thin film with titanium silicide and germanium targets, were demonstrated for low temperature applications of nonvolatile memory. Formation and composition characteristics of nanocrystals (NCs) at various annealing temperatures were examined by transmission electron microscopy and X-ray photon-emission spectroscopy, respectively. It was observed that the addition of germanium (Ge) significantly reduces the proposed thermal budget necessary for Ti-based NC formation due to the rise of morphological instability and agglomeration properties during annealing. NC structures formed after annealing at 500 degrees C, and separated well at 600 degrees C annealing. However, it was also observed that significant thermal desorption of Ge atoms occurs at 600 degrees C due to the sublimation of formatted GeO phase and results in a serious decrease of memory window. Therefore, an approach to effectively restrain Ge thermal desorption is proposed by encapsulating the Ti-based trapping layer with a thick silicon oxide layer before 600 degrees C annealing. The electrical characteristics of data retention in the sample with the 600 degrees C annealing exhibited better performance than the 500 C-annealed sample, a result associated with the better separation and better crystallization of the NC structures. (C) 2011 Elsevier B.V. All rights reserved.
Nonvolatile memory effect of tungsten nanocrystals under oxygen plasma treatments
(2010-10-01)
Chen, Shih-Cheng
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Chang, Ting-Chang
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Chen, Wei-Ren
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Lo, Yuan-Chun
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Wu, Kai-Ting
In this work, an oxygen plasma treatment was used to improve the memory effect of nonvolatile W nanocrystal memory, including memory window, retention and endurance. To investigate the role of the oxygen plasma treatment in charge storage characteristics, the X-ray photon-emission spectra (XPS) were performed to analyze the variation of chemical composition for W nanocrystal embedded oxide both with and without the oxygen plasma treatment. In addition, the transmission electron microscopy (TEM) analyses were also used to identify the microstructure in the thin film and the size and density of W nanocrystals. The device with the oxygen plasma treatment shows a significant improvement of charge storage effect, because the oxygen plasma treatment enhanced the quality of silicon oxide surrounding the W nanocrystals. Therefore, the data retention and endurance characteristics were also improved by the passivation. (C) 2010 Elsevier B.V. All rights reserved.
Nonvolatile memory effect of tungsten nanocrystals under oxygen plasma treatments
(2010-10-01)
Chen, Shih-Cheng
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Chang, Ting-Chang
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Chen, Wei-Ren
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Lo, Yuan-Chun
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Wu, Kai-Ting
In this work, an oxygen plasma treatment was used to improve the memory effect of nonvolatile W nanocrystal memory, including memory window, retention and endurance. To investigate the role of the oxygen plasma treatment in charge storage characteristics, the X-ray photon-emission spectra (XPS) were performed to analyze the variation of chemical composition for W nanocrystal embedded oxide both with and without the oxygen plasma treatment. In addition, the transmission electron microscopy (TEM) analyses were also used to identify the microstructure in the thin film and the size and density of W nanocrystals. The device with the oxygen plasma treatment shows a significant improvement of charge storage effect, because the oxygen plasma treatment enhanced the quality of silicon oxide surrounding the W nanocrystals. Therefore, the data retention and endurance characteristics were also improved by the passivation. (C) 2010 Elsevier B.V. All rights reserved.
Reproducible resistance switching of a relatively thin FeO(x) layer produced by oxidizing the surface of a FePt electrode in a metal-oxide-metal structure
(2010-12-30)
Feng, Li-Wei
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Chang, Yao-Feng
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Chang, Chun-Yen
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Chang, Ting-Chang
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Wang, Shin-Yuan
In this study, reproducible resistance switching effects were demonstrated on a relatively thin FeO(x) layer in the TiN/SiO(2)/FeO(x)/FePt structure produced by oxidizing the surface of a FePt electrode during a plasma-enhanced tetraethyl orthosilicate oxide deposition process. Characteristics of the non-stoichiometric FeO(x) transition layer were examined by Auger electron spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy analyses. In addition, characteristics of the forming process as well as the current transport characteristics after forming process in the TiN/SiO(2)/FeO(x)/FePt structure were discussed. Moreover, the role of the silicon oxide layer was also experimentally demonstrated to act as an additional supplier of oxygen ions for the switching requirement by biasing high voltage bias conditions. (C) 2010 Elsevier B.V. All rights reserved.