Browsing by Author "Lee, Dai-Ying"

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A Comprehensive Study of 3-stage High Resistance State Retention Behavior for TMO ReRAMs from Single Cells to a Large Array
(2017-01-01)
Lin, Yu-Hsuan
;
Ho, Yung-Han
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Lee, Ming-Hsiu
;
Wang, Chao-Hung
;
Lin, Yu-Yu
For the first time the retention of high resistance state (HRS) in resistive random access memory (ReRAM) is found to compose of three stages - extending tail-bits, distribution shift, and then distribution broadening. This work provides a comprehensive study on the HRS's retention behavior in WOx-based ReRAMs from single device characteristics to group distribution. Different from conventional activation energy (Ea) analysis, the mean and variance of the array distribution are presented to overcome the non-uniform Ea issue. Since the extracted Ea fits well with Vo(2+) (oxygen vacancy) migration characteristics, the three retention stages are suggested to be the competing results from the migration, recombination, and generation of the Vo(2+) and O2- in the gap region. A three-dimensional retention model with kinetic Monte Carlo simulator and trap-assisted tunneling conduction is proposed to discuss the dominating mechanism in different time and temperature scales. The mechanism for random telegraph noise is also included to illustrate the fluctuating nature of the HRS cells.
A Novel Varying-Bias Read Scheme for MLC and Wide Temperature Range TMO ReRAM
(2016-11)
Lin, Yu-Hsuan
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Lee, Ming-Hsiu
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Wu, Jau-Yi
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Lin, Yu-Yu
;
Lee, Feng-Ming
Resistance of transition metal oxide (TMO) resistive random access memory (ReRAM) depends sharply on temperature, resulting in drastic memory window loss at high temperature. Thus, it is difficult to design the ReRAM that can serve a wide range of operating conditions. It is especially challenging to achieve multi-level-cell (MLC) ReRAM because of the large temperature dependency. This letter investigates both the temperature and read bias dependencies of WOx ReRAM, and found both can be well understood by a modified space-charge limited conduction model. Using this model, we have designed a novel read scheme that varies the read bias according to the device temperature and compensates for the temperature effect on cell resistance. Since TMO ReRAM devices depend on defect states, cell-to-cell and cycle-to-cycle variations are naturally large. An algorithm is designed to address the variability. A 1-Mb WOx ReRAM array is fabricated to both characterize the bias and temperature dependencies and verify the new read scheme. A large and constant memory window is preserved for MLC across a wide temperature range (-40 degrees C-125 degrees C), suitable for high-reliability applications.
Bottom Electrode Modification of ZrO2 Resistive Switching Memory Device with Au Nanodots
(2012-02-01)
Lee, Dai-Ying
;
Yao, I-Chuan
;
Tseng, Tseung-Yuen
;
材料科學與工程學系
;
電子工程學系及電子研究所
The resistive switching properties of the ZrO2 memory devices with bottom electrode modification by using Au nanodots are investigated in this study. The regular arrays of Au nanodots are fabricated on Pt bottom electrode by nanosphere lithography. Due to the tip of the Au nanodots on the Pt bottom electrode, it causes the higher electric field within the ZrO2 film above the nanodots due to reduced effective film thickness and induces the localized conducting filaments easily. The operation parameters' variation for switching devices is, therefore, suppressed with lower operation voltage and resistance ratio. Long retention time (> 10(6) s) and stubborn nondestructive readout test (> 10(4) s) at room temperature and 150 degrees C are also demonstrated in this device. (C) 2012 The Japan Society of Applied Physics
Controllable oxygen vacancies to enhance resistive switching performance in a ZrO(2)-based RRAM with embedded Mo layer
(2010-12-10)
Wang, Sheng-Yu
;
Lee, Dai-Ying
;
Huang, Tai-Yuen
;
Wu, Jia-Woei
;
Tseng, Tseung-Yuen
In this study, the resistive switching characteristics of a ZrO(2)-based memory film with an embedded Mo layer are investigated. The experimental results show that the forming process can be removed by inserting an embedded Mo metal layer within ZrO(2) via a post-annealing process. The excellent memory performance, which includes lower operation voltage (<1.5 V), good endurance (>10(3) cycles), a stubborn nondestructive readout property (>10(4) s), and long retention time (>10(7) s), is also demonstrated. Moreover, high-speed operation (10 ns) can be successively maintained over 10(3) cycles without any operational errors observed in this memory device. Due to the interface layer induced by the Ti top electrode, the formation and rupture of conducting filaments are suggested to occur near the Ti/ZrO(2) interface. The oxygen vacancies induced by the embedded Mo can enhance the formation of conducting filaments and further improve the switching characteristics in ZrO(2)-based devices.
Controllable oxygen vacancies to enhance resistive switching performance in a ZrO2-based RRAM with embedded Mo layer
(2010-12-10)
Wang, Sheng-Yu
;
Lee, Dai-Ying
;
Huang, Tai-Yuen
;
Wu, Jia-Woei
;
Tseng, Tseung-Yuen
In this study, the resistive switching characteristics of a ZrO2-based memory film with an embedded Mo layer are investigated. The experimental results show that the forming process can be removed by inserting an embedded Mo metal layer within ZrO2 via a post-annealing process. The excellent memory performance, which includes lower operation voltage (<1.5 V), good endurance (>10(3) cycles), a stubborn nondestructive readout property (>10(4) s), and long retention time (>10(7) s), is also demonstrated. Moreover, high-speed operation (10 ns) can be successively maintained over 10(3) cycles without any operational errors observed in this memory device. Due to the interface layer induced by the Ti top electrode, the formation and rupture of conducting filaments are suggested to occur near the Ti/ZrO2 interface. The oxygen vacancies induced by the embedded Mo can enhance the formation of conducting filaments and further improve the switching characteristics in ZrO2-based devices.
Effect of thermal treatment on resistive switching characteristics in Pt/Ti/Al(2)O(3)/Pt devices
(2008-12-25)
Lin, Chih-Yang
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Lee, Dai-Ying
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Wang, Sheng-Yi
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Lin, Chun-Chieh
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Tseng, Tseung-Yuen
Resistive switching characteristics of Pt/Ti/Al(2)O(3)/Pt memory devices annealed at various temperatures including 400 degrees C, 500 degrees C and 600 degrees C for 1 h under ambient condition were investigated in the study. The Al(2)O(3) thin films annealed at up to 600 degrees C for 1 h remain amorphous phase based on the X-ray diffraction (XRD) analyses. As increasing annealing temperature, the forming voltage (activating the pristine device) of the memory device decreases in contrast to the rising trend of the turn-on voltage (switching from high to low resistance state). However, the turn-off voltage (switching from low to high resistance state) is almost uninfluenced by thermal annealing. These phenomena might be attributed to the interdiffusion between Ti and Al(2)O(3), based on the analyzed results of secondary ion mass spectroscopy (SIMS) and high resolution transmission electron microscope (HR-TEM). Moreover, the thermal annealing process eventually creates high conducting paths with a high density of oxygen vacancies between the two electrodes. (c) 2008 Elsevier B.V. All rights reserved.
Effect of thermal treatment on resistive switching characteristics in Pt/Ti/Al2O3/Pt devices
(2008-12-25)
Lin, Chih-Yang
;
Lee, Dai-Ying
;
Wang, Sheng-Yi
;
Lin, Chun-Chieh
;
Tseng, Tseung-Yuen
Resistive switching characteristics of Pt/Ti/Al2O3/Pt memory devices annealed at various temperatures including 400 degrees C, 500 degrees C and 600 degrees C for 1 h under ambient condition were investigated in the study. The Al2O3 thin films annealed at up to 600 degrees C for 1 h remain amorphous phase based on the X-ray diffraction (XRD) analyses. As increasing annealing temperature, the forming voltage (activating the pristine device) of the memory device decreases in contrast to the rising trend of the turn-on voltage (switching from high to low resistance state). However, the turn-off voltage (switching from low to high resistance state) is almost uninfluenced by thermal annealing. These phenomena might be attributed to the interdiffusion between Ti and Al2O3, based on the analyzed results of secondary ion mass spectroscopy (SIMS) and high resolution transmission electron microscope (HR-TEM). Moreover, the thermal annealing process eventually creates high conducting paths with a high density of oxygen vacancies between the two electrodes. (c) 2008 Elsevier B.V. All rights reserved.
Effects of Ti top electrode thickness on the resistive switching behaviors of rf-sputtered ZrO(2) memory films
(2009-09-14)
Wang, Sheng-Yu
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Lee, Dai-Ying
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Tseng, Tseung-Yuen
;
Lin, Chih-Yang
;
電子工程學系及電子研究所
In this study, we propose a simple method to produce the various interface thicknesses within Ti/ZrO(2) by changing the thickness of the Ti top electrode. As the Ti thickness increases, the induced interface thickness also increases to degrade the dielectric strength of the ZrO(2), further lowering the forming voltage. However, when the interface layer is thick enough, it will trap sufficient charges to build up an opposite electric field to increase the forming voltage. The induced interface thickness is found to obviously affect the bias polarity of the resistive switching behavior and the device reliability. A fluctuant ON process is also demonstrated to be attributed to the competition between the formation and rupture of the conducting filaments. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3231872]
Effects of Ti top electrode thickness on the resistive switching behaviors of rf-sputtered ZrO2 memory films
(2009-09-14)
Wang, Sheng-Yu
;
Lee, Dai-Ying
;
Tseng, Tseung-Yuen
;
Lin, Chih-Yang
;
電子工程學系及電子研究所
In this study, we propose a simple method to produce the various interface thicknesses within Ti/ZrO2 by changing the thickness of the Ti top electrode. As the Ti thickness increases, the induced interface thickness also increases to degrade the dielectric strength of the ZrO2, further lowering the forming voltage. However, when the interface layer is thick enough, it will trap sufficient charges to build up an opposite electric field to increase the forming voltage. The induced interface thickness is found to obviously affect the bias polarity of the resistive switching behavior and the device reliability. A fluctuant ON process is also demonstrated to be attributed to the competition between the formation and rupture of the conducting filaments. (C) 2009 American Institute of Physics. [doi: 10.1063/1.3231872]
Electrical properties and fatigue behaviors of ZrO(2) resistive switching thin films
(2008-01-01)
Lin, Chih-Yang
;
Wang, Sheng-Yi
;
Lee, Dai-Ying
;
Tseng, Tseung-Yuen
;
電子工程學系及電子研究所
The resistive switching mechanisms of ZrO(2) memory films are proposed to explain why resistive switching characteristics of Ti/ZrO(2)/Pt device are more stable than those of Pt/ZrO(2)/Pt and Al/ZrO(2)/Pt devices in this study. Different from the Pt/ZrO(2)/Pt and the Al/ZrO(2)/Pt devices, the carrier conduction mechanisms in the Ti/ZrO(2)/Pt device obey space charge limited current theory, which may be caused by the formation of the interface layer between Ti and ZrO(2). Moreover, the resistive switching mechanisms are proposed to be related to the filament formation/rupture theory and oxygen ion migration. The location where filament formation/rupture takes place should be confined near the interface between Ti and ZrO(2), leading to the stable resistive switching characteristics and a better endurance performance. During successive resistive cycles at room temperature and 150 degrees C, the fatigue behaviors are observed due to the degradation of both two memory states, which might be related to the transformation of the interface layers between Ti and ZrO(2) and the coalescence of ZrO(x) clusters. (C) 2008 The Electrochemical Society.
Electrical properties and fatigue behaviors of ZrO2 resistive switching thin films
(2008-01-01)
Lin, Chih-Yang
;
Wang, Sheng-Yi
;
Lee, Dai-Ying
;
Tseng, Tseung-Yuen
;
電子工程學系及電子研究所
The resistive switching mechanisms of ZrO2 memory films are proposed to explain why resistive switching characteristics of Ti/ZrO2/Pt device are more stable than those of Pt/ZrO2/Pt and Al/ZrO2/Pt devices in this study. Different from the Pt/ZrO2/Pt and the Al/ZrO2/Pt devices, the carrier conduction mechanisms in the Ti/ZrO2/Pt device obey space charge limited current theory, which may be caused by the formation of the interface layer between Ti and ZrO2. Moreover, the resistive switching mechanisms are proposed to be related to the filament formation/rupture theory and oxygen ion migration. The location where filament formation/rupture takes place should be confined near the interface between Ti and ZrO2, leading to the stable resistive switching characteristics and a better endurance performance. During successive resistive cycles at room temperature and 150 degrees C, the fatigue behaviors are observed due to the degradation of both two memory states, which might be related to the transformation of the interface layers between Ti and ZrO2 and the coalescence of ZrOx clusters. (C) 2008 The Electrochemical Society.
Excellent High Temperature Retention of TiOXNV ReRAM by Interfacial Layer Engineering
(2018-01-01)
Lin, Yu-Hsuan
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Lee, Dai-Ying
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Wang, Chao-Hung
;
Lee, Ming-Hsiu
;
Ho, Yung-Han
Since the resistance switching of the transition metal oxide (TMO) resistive random access memory (ReRAM) is based on thc interaction between the oxygen ions and vacancies, the unintentional oxygen/vacancy reaction should be avoided during data retention. This work demonstrates significant improvements on the retention performance by inserting a Si layer in the TiO Ny ReRAM to block the diffusion of oxygen ions through the Ti/TiO,N interface. The mechanism and factors that influenced thc IIRS and LRS retention arc also studied. The retention performance of HRS is correlated with its RESET level while the LRS retention depends on the programming current. The proposed Ti/Si/TiO,N, ReRAMs can switch for more than 103 cycles from array testing results.
Excellent Resistance Variability Control of WOx ReRAM by a Smart Writing Algorithm
(2016)
Lin, Yu-Hsuan
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Wu, Jau-Yi
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Lee, Ming-Hsiu
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Wang, Tien-Yen
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Lin, Yu-Yu
TMO ReRAMs, being built on defect states, are intrinsically subject to variability. In this work, cell to cell variability is studied by applying write shots with different current and voltage for Forming, SET and RESET operation, respectively. We found the keys to eliminate tail bits consist of (1) longer write pulse, (2) higher write current and (3) higher write voltage. In order to optimize the performance of write speed, write power and device reliability, we developed a novel resistance control method using a smart writing algorithm. Compared to the conventional ISPP writing scheme, this smart writing algorithm covers much wider switching condition variability and cell-to-cell variation by controlling both current and voltage for ReRAM operation.
Fabrication and resistive switching characteristics of high compact Ga-doped ZnO nanorod thin film devices
(2012-04-13)
Yao, I-Chuan
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Lee, Dai-Ying
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Tseng, Tseung-Yuen
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Lin, Pang
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材料科學與工程學系
This study investigates the resistive switching behavior of Ga-doped ZnO (GZO) nanorod thin films with various Ga/Zn molar ratios. Vertically well-aligned and uniform GZO nanorod thin films were successfully grown on Au/Ti/SiO2/p-Si substrates using an aqueous solution method. X-ray diffraction (XRD) results indicate that GZO nanorods have [0001] highly preferred orientation. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) observations show the formation of highly ordered and dense nanorod thin films. These compact GZO nanorod thin films can be used to make resistive switching memory devices. Such memory devices can be reversibly switched between ON and OFF states, with a stable resistance ratio of ten times, narrow dispersion of ON and OFF voltages, and good endurance performance of over 100 cycles. The resistive switching mechanism in these devices is related to the formation and rupture of conducting filaments consisting of oxygen vacancies, occurring at interfaces between GZO nanorods (grain boundaries). Results show that the resulting compact GZO nanorod thin films have a high potential for resistive memory applications.
Forming-free resistive switching behaviors in Cr-embedded Ga(2)O(3) thin film memories
(2011-12-01)
Lee, Dai-Ying
;
Tseng, Tseung-Yuen
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電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Resistive switching behaviors are studied for the rapid thermal annealing (RTA) Ga(2)O(3) thin film embedding a Cr metal layer. By modifying the thickness, area, and RTA temperature of the device, the thermal-induced resistive switching is similar to those induced by the electrical forming process. The conducting filaments composed of oxygen vacancies are created by the Cr diffusion and oxidization during RTA. The related carrier conduction mechanism obeys space charge limited conduction theory accompanied by the formation/rupture of the conducting filaments at the interface between Ti and Cr:Ga(2)O(3) film. This study demonstrates a convenient process to fabricate forming-free resistive switching memory devices. (C) 2011 American Institute of Physics. [doi:10.1063/1.3665871]
Forming-free resistive switching behaviors in Cr-embedded Ga2O3 thin film memories
(2011-12-01)
Lee, Dai-Ying
;
Tseng, Tseung-Yuen
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
Resistive switching behaviors are studied for the rapid thermal annealing (RTA) Ga2O3 thin film embedding a Cr metal layer. By modifying the thickness, area, and RTA temperature of the device, the thermal-induced resistive switching is similar to those induced by the electrical forming process. The conducting filaments composed of oxygen vacancies are created by the Cr diffusion and oxidization during RTA. The related carrier conduction mechanism obeys space charge limited conduction theory accompanied by the formation/rupture of the conducting filaments at the interface between Ti and Cr:Ga2O3 film. This study demonstrates a convenient process to fabricate forming-free resistive switching memory devices. (C) 2011 American Institute of Physics. [doi:10.1063/1.3665871]
Improved resistive switching properties of Ti/ZrO(2)/Pt memory devices for RRAM application
(2011-07-01)
Wang, Sheng-Yu
;
Tsai, Chen-Han
;
Lee, Dai-Ying
;
Lin, Chih-Yang
;
Lin, Chun-Chieh
In this study, we have investigated the effect of current compliance during forming process on resistive switching (RS) characteristics of the Ti/ZrO(2)/Pt device. The higher the current compliance is, the larger RS operation voltage is needed. The Ti/ZrO(2)/Pt device with high device yield can be operated over 10,000 RS cycles by sweeping dc voltage. and the on and off two memory states exhibit good stability under 0.3 V stress voltage. Moreover, the data retention of both memory states is over 10(5) s. As applying +6-V 10-ns and -3-V 10-ns voltage pulses on the device, there are operation errors observed during continuous write-read-erase-read cycles until increasing the pulse width to 50 ns. Nondestructive readout tests are also performed on the Ti/ZrO(2)/Pt device before and after 10(3) pulse cycles without any obvious degradation observed. Compared with reported ZrO(2)-based memory devices, our Ti/ZrO(2)/Pt device exhibits better RS properties and has a high potential for memory application. (C) 2011 Elsevier B.V. All rights reserved.
Improved resistive switching properties of Ti/ZrO2/Pt memory devices for RRAM application
(2011-07-01)
Wang, Sheng-Yu
;
Tsai, Chen-Han
;
Lee, Dai-Ying
;
Lin, Chih-Yang
;
Lin, Chun-Chieh
In this study, we have investigated the effect of current compliance during forming process on resistive switching (RS) characteristics of the Ti/ZrO2/Pt device. The higher the current compliance is, the larger RS operation voltage is needed. The Ti/ZrO2/Pt device with high device yield can be operated over 10,000 RS cycles by sweeping dc voltage. and the on and off two memory states exhibit good stability under 0.3 V stress voltage. Moreover, the data retention of both memory states is over 10(5) s. As applying +6-V 10-ns and -3-V 10-ns voltage pulses on the device, there are operation errors observed during continuous write-read-erase-read cycles until increasing the pulse width to 50 ns. Nondestructive readout tests are also performed on the Ti/ZrO2/Pt device before and after 10(3) pulse cycles without any obvious degradation observed. Compared with reported ZrO2-based memory devices, our Ti/ZrO2/Pt device exhibits better RS properties and has a high potential for memory application. (C) 2011 Elsevier B.V. All rights reserved.
Multilevel resistive switching in Ti/Cu(x)O/Pt memory devices
(2010-12-01)
Wang, Sheng-Yu
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Huang, Chin-Wen
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Lee, Dai-Ying
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Tseng, Tseung-Yuen
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Chang, Ting-Chang
The multilevel resistive switching (RS) behaviors of the Ti/Cu(x)O/Pt device were investigated by controlling the operated parameters of current and voltage bias in this study. We demonstrated that at least five-level memory states for data storage could be determined by controlling the current compliance, the span of voltage sweeping, and the amplitude of voltage pulse imposed on the memory device. During the dc voltage sweeping mode, not only the multilevel ON-states but also the multilevel OFF-states were achieved for the multilevel storage. The RS mechanism of the Ti/Cu(x)O/Pt device is proposed to be related to the formation/rupture of the conducting filaments, arising from the interfacial oxygen ion migration between the Ti top electrode and Cu(x)O films. Moreover, a possible conduction scenario for the multilevel RS behaviors is also suggested. Owing to all the multilevel memory states are distinguishable and possess the nondestructive readout property, it implies that the Ti/Cu(x)O/Pt device has the promising potential for the future multilevel-capability memory cell application. (c) 2010 American Institute of Physics. [doi:10.1063/1.3518514]
Multilevel resistive switching in Ti/CuxO/Pt memory devices
(2010-12-01)
Wang, Sheng-Yu
;
Huang, Chin-Wen
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Lee, Dai-Ying
;
Tseng, Tseung-Yuen
;
Chang, Ting-Chang
The multilevel resistive switching (RS) behaviors of the Ti/CuxO/Pt device were investigated by controlling the operated parameters of current and voltage bias in this study. We demonstrated that at least five-level memory states for data storage could be determined by controlling the current compliance, the span of voltage sweeping, and the amplitude of voltage pulse imposed on the memory device. During the dc voltage sweeping mode, not only the multilevel ON-states but also the multilevel OFF-states were achieved for the multilevel storage. The RS mechanism of the Ti/CuxO/Pt device is proposed to be related to the formation/rupture of the conducting filaments, arising from the interfacial oxygen ion migration between the Ti top electrode and CuxO films. Moreover, a possible conduction scenario for the multilevel RS behaviors is also suggested. Owing to all the multilevel memory states are distinguishable and possess the nondestructive readout property, it implies that the Ti/CuxO/Pt device has the promising potential for the future multilevel-capability memory cell application. (c) 2010 American Institute of Physics. [doi:10.1063/1.3518514]