Browsing by Author "Wu, Ming-Chi"

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A study on low-power, nanosecond operation and multilevel bipolar resistance switching in Ti/ZrO2/Pt nonvolatile memory with 1T1R architecture
(2012-06-01)
Wu, Ming-Chi
;
Jang, Wen-Yueh
;
Lin, Chen-Hsi
;
Tseng, Tseung-Yuen
;
電子工程學系及電子研究所
Low-power, bipolar resistive switching (RS) characteristics in the Ti/ZrO2/Pt nonvolatile memory with one transistor and one resistor (1T1R) architecture were reported. Multilevel storage behavior was observed by modulating the amplitude of the MOSFET gate voltage, in which the transistor functions as a current limiter. Furthermore, multilevel storage was also executed by controlling the reset voltage, leading the resistive random access memory (RRAM) to the multiple metastable low resistance state (LRS). The experimental results on the measured electrical properties of the various sized devices confirm that the RS mechanism of the Ti/ZrO2/Pt structure obeys the conducting filaments model. In application, the devices exhibit high-speed switching performances (250 ns) with suitable high/low resistance state ratio (HRS/LRS > 10). The LRS of the devices with 10 year retention ability at 80 degrees C, based on the Arrhenius equation, is also demonstrated in the thermal accelerating test. Furthermore, the ramping gate voltage method with fixed drain voltage is used to switch the 1T1R memory cells for upgrading the memory performances. Our experimental results suggest that the ZrO2-based RRAM is a prospective alternative for nonvolatile multilevel memory device applications.
Effects of Vanadium Doping on Resistive Switching Characteristics and Mechanisms of SrZrO(3)-Based Memory Films
(2010-08-01)
Lin, Meng-Han
;
Wu, Ming-Chi
;
Lin, Chen-Hsi
;
Tseng, Tseung-Yuen
;
電子工程學系及電子研究所
The effects of vanadium doping on resistive switching (RS) characteristics and mechanisms of RF-sputtered SrZrO(3) (SZO)-based thin films are investigated in this paper. The physical and electrical properties of SZO-based thin films are modulated by vanadium doping due to the Zr(4+) ion replaced by V(5+), further affecting the RS parameters of SZO-based thin films. The conduction mechanisms of SZO-based thin films are dominated by ohmic conduction (hoping conduction) and Frenkel-Poole emission for the low resistance state (LRS) and the high resistance state (HRS), respectively. The turn-on process might be attributed to the formation of conducting filaments consisting of oxygen vacancies with the effective barrier height (phi(B,eff)) in the range of 0.10-0.13 eV, whereas the turn-off process might result from thermally assisted oxidation of oxygen vacancies by the Joule heating effect. Furthermore, the introduction of the high valence cation (V(5+)) in a Zr(4+) site of SZO crystalline structure can suppress the formation of oxygen vacancies due to the charge neutrality restriction. Such suppression leads to the changes in the forming voltage, turn-on voltage, HRS resistance, dielectric constant, and phi(B,eff) with vanadium doping concentration up to 0.2 mol%, which is within the solid solubility limit based on our measured lattice constants and Vegard's law.
Effects of Vanadium Doping on Resistive Switching Characteristics and Mechanisms of SrZrO3-Based Memory Films
(2010-08-01)
Lin, Meng-Han
;
Wu, Ming-Chi
;
Lin, Chen-Hsi
;
Tseng, Tseung-Yuen
;
電子工程學系及電子研究所
The effects of vanadium doping on resistive switching (RS) characteristics and mechanisms of RF-sputtered SrZrO3 (SZO)-based thin films are investigated in this paper. The physical and electrical properties of SZO-based thin films are modulated by vanadium doping due to the Zr4+ ion replaced by V5+, further affecting the RS parameters of SZO-based thin films. The conduction mechanisms of SZO-based thin films are dominated by ohmic conduction (hoping conduction) and Frenkel-Poole emission for the low resistance state (LRS) and the high resistance state (HRS), respectively. The turn-on process might be attributed to the formation of conducting filaments consisting of oxygen vacancies with the effective barrier height (phi(B,eff)) in the range of 0.10-0.13 eV, whereas the turn-off process might result from thermally assisted oxidation of oxygen vacancies by the Joule heating effect. Furthermore, the introduction of the high valence cation (V5+) in a Zr4+ site of SZO crystalline structure can suppress the formation of oxygen vacancies due to the charge neutrality restriction. Such suppression leads to the changes in the forming voltage, turn-on voltage, HRS resistance, dielectric constant, and phi(B,eff) with vanadium doping concentration up to 0.2 mol%, which is within the solid solubility limit based on our measured lattice constants and Vegard's law.
High Device Yield of Resistive Switching Characteristics in Oxygen-Annealed SrZrO(3) Memory Devices
(2011-04-01)
Lin, Meng-Han
;
Wu, Ming-Chi
;
Huang, Yi-Han
;
Lin, Chen-Hsi
;
Tseng, Tseung-Yuen
This paper reports the effects of rapid thermal annealing (RTA) on resistive switching (RS) characteristics and mechanisms of SrZrO(3) (SZO)-based memory devices. SZO thin films were deposited on LaNiO(3) (LNO) (100)/Pt/Ti/SiO(2)/Si using radio-frequency magnetron sputtering and were followed by an RTA process in N(2), Ar, and O(2) ambients, respectively, at various temperatures for improving RS performance. Experimental results indicate that an SZO device annealed in O(2) at 600 degrees C (O(2)-600) exhibits stable RS properties and has a high device yield (similar to 90%), a reliable retention characteristic (up to 1 x 10(6) s at 100 degrees C), and steady nondestructive readout properties (over 1.4 x 10(4) s at 100 degrees C). However, by increasing RTA temperature to more than 700 degrees C, random formation of LNO (110) precipitates on the bottom surface of SZO grains might shorten the effective thickness of the SZO thin films. Furthermore, a strong electric field possibly occurs at the region between Al top electrodes and low-resistivity LNO precipitates. It is speculated that an RS phenomenon, which occurs within SZO grains instead of on grain boundaries, easily leads to RS failure, further resulting in severe degradation of device yield in the O(2)-700 and O(2)-800 devices. When compared with other devices, O(2)-600 SZO memory devices exhibit highly reliable RS characteristics.
High Device Yield of Resistive Switching Characteristics in Oxygen-Annealed SrZrO3 Memory Devices
(2011-04-01)
Lin, Meng-Han
;
Wu, Ming-Chi
;
Huang, Yi-Han
;
Lin, Chen-Hsi
;
Tseng, Tseung-Yuen
This paper reports the effects of rapid thermal annealing (RTA) on resistive switching (RS) characteristics and mechanisms of SrZrO3 (SZO)-based memory devices. SZO thin films were deposited on LaNiO3 (LNO) (100)/Pt/Ti/SiO2/Si using radio-frequency magnetron sputtering and were followed by an RTA process in N-2, Ar, and O-2 ambients, respectively, at various temperatures for improving RS performance. Experimental results indicate that an SZO device annealed in O-2 at 600 degrees C (O-2-600) exhibits stable RS properties and has a high device yield (similar to 90%), a reliable retention characteristic (up to 1 x 10(6) s at 100 degrees C), and steady nondestructive readout properties (over 1.4 x 10(4) s at 100 degrees C). However, by increasing RTA temperature to more than 700 degrees C, random formation of LNO (110) precipitates on the bottom surface of SZO grains might shorten the effective thickness of the SZO thin films. Furthermore, a strong electric field possibly occurs at the region between Al top electrodes and low-resistivity LNO precipitates. It is speculated that an RS phenomenon, which occurs within SZO grains instead of on grain boundaries, easily leads to RS failure, further resulting in severe degradation of device yield in the O-2-700 and O-2-800 devices. When compared with other devices, O-2-600 SZO memory devices exhibit highly reliable RS characteristics.
High-speed and localized resistive switching characteristics of double-layer SrZrO(3) memory devices
(2010-07-28)
Lin, Meng-Han
;
Wu, Ming-Chi
;
Huang, Chun-Yang
;
Lin, Chen-Hsi
;
Tseng, Tseung-Yuen
The fabrication of SrZrO(3) (SZO) memory devices with oxygen-rich (OR) and oxygen-deficient (OD) double layers, their resistive switching (RS) characteristics and mechanisms are investigated in this study. Due to the difference in oxygen content between the OR and OD layers formed by an oxygen flow control (OFC) process during SZO deposition, the RS region is effectively reduced and localized within the OR layer, which leads to a low operation voltage and stable RS behaviours. Furthermore, the OFC SZO device exhibits high-speed switching (10 ns) over 400 times and long retention (>10(6) s), showing promising potential for next-generation nonvolatile memory applications.
High-speed and localized resistive switching characteristics of double-layer SrZrO3 memory devices
(2010-07-28)
Lin, Meng-Han
;
Wu, Ming-Chi
;
Huang, Chun-Yang
;
Lin, Chen-Hsi
;
Tseng, Tseung-Yuen
The fabrication of SrZrO3 (SZO) memory devices with oxygen-rich (OR) and oxygen-deficient (OD) double layers, their resistive switching (RS) characteristics and mechanisms are investigated in this study. Due to the difference in oxygen content between the OR and OD layers formed by an oxygen flow control (OFC) process during SZO deposition, the RS region is effectively reduced and localized within the OR layer, which leads to a low operation voltage and stable RS behaviours. Furthermore, the OFC SZO device exhibits high-speed switching (10 ns) over 400 times and long retention (>10(6) s), showing promising potential for next-generation nonvolatile memory applications.
Highly Stable SrZrO3 Bipolar Resistive Switching Memory by Ti Modulation Layer
(2010)
Wu, Ming-Chi
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Lin, Meng-Han
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Yeh, Yu-Ting
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Lin, Chen-Hsi
;
Tseng, Tseung-Yuen
In this study, we investigated the resistive switching characteristics of the SrZrO3 (SZO)-based resistance random access memory (RRAM). After the sequential thin-films Pt/Ti/SZO/LaNiO3 deposition, the post annealing (PA) treatment under various conditions was carried out to form the interfacial layer (TiOx) between Ti and SZO. It can be proved that the Ti modulation layer act as an oxygen getter can modify the resistive switching property of RRAM. With the suitable thickness of Ti layer and the proper annealing temperature, the SZO-based RRAM device could have a lower operation voltage, a lower compliance current a long retention behavior, and stable resistance ratio over 10(4) s under 0.3 V reading voltage.
Improvement of resistive switching characteristics in SrZrO3 thin films with embedded Cr layer
(2008-10-01)
Lin, Chih-Yang
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Lin, Meng-Han
;
Wu, Ming-Chi
;
Lin, Chen-Hsi
;
Tseng, Tseung-Yuen
The stabilization of the resistive switching properties is necessary to realize the memory application of the SrZrO3 (SZO)-based resistive switching devices. During continuous resistive switching cycle, broad variations of the resistive switching parameters of the SZO-based memory devices can be improved by a thin embedded Cr layer. The Cr metal layer is proposed to diffuse into and dope the SZO thin film to produce the space charge region, further reducing the effective resistive switching region. Hence, the good stabilization of the resistive switching properties can be obtained in the SZO films with embedded Cr layer.
Low-Power and Highly Reliable Multilevel Operation in ZrO(2) 1T1R RRAM
(2011-08-01)
Wu, Ming-Chi
;
Lin, Yi-Wei
;
Jang, Wen-Yueh
;
Lin, Chen-Hsi
;
Tseng, Tseung-Yuen
The Ti/ZrO(2)/Pt resistive memory devices with one transistor and one resistor (1T1R) architecture are successfully fabricated in this letter. The tested devices show low operation current (20 mu A), low switching voltage (set/reset, 0.8/-1 V), and reliable data retention for low-resistance state (LRS) with a 20-mu A set current at 80 degrees C (over ten years) via an excellent current limiter, namely, a metal-oxide-semiconductor field-effect transistor (MOSFET). In addition, multilevel storage characteristics are also demonstrated by modulating the amplitude of the MOSFET gate voltage. The various LRS levels obtained are possibly attributed to the formation of different numbers and sizes of conducting filaments consisting of oxygen vacancies caused by an external electric field. Moreover, reproducible resistive switching characteristics up to 2000 switching cycles are achieved in the same device. Our 1T1R ZrO(2)-based resistive switching access memory with low-power and highly reliable multilevel operation has high potential for practical applications.
Low-Power and Highly Reliable Multilevel Operation in ZrO2 1T1R RRAM
(2011-08-01)
Wu, Ming-Chi
;
Lin, Yi-Wei
;
Jang, Wen-Yueh
;
Lin, Chen-Hsi
;
Tseng, Tseung-Yuen
The Ti/ZrO2/Pt resistive memory devices with one transistor and one resistor (1T1R) architecture are successfully fabricated in this letter. The tested devices show low operation current (20 mu A), low switching voltage (set/reset, 0.8/-1 V), and reliable data retention for low-resistance state (LRS) with a 20-mu A set current at 80 degrees C (over ten years) via an excellent current limiter, namely, a metal-oxide-semiconductor field-effect transistor (MOSFET). In addition, multilevel storage characteristics are also demonstrated by modulating the amplitude of the MOSFET gate voltage. The various LRS levels obtained are possibly attributed to the formation of different numbers and sizes of conducting filaments consisting of oxygen vacancies caused by an external electric field. Moreover, reproducible resistive switching characteristics up to 2000 switching cycles are achieved in the same device. Our 1T1R ZrO2-based resistive switching access memory with low-power and highly reliable multilevel operation has high potential for practical applications.
Nonpolar Bistable Resistive Switching Behaviors of Bismuth Titanate Oxide Thin Film
(2009)
Lin, Meng-Han
;
Wu, Ming-Chi
;
Lin, Chun-Chieh
;
Tseng, Tseung-Yuen
;
電子工程學系及電子研究所
Nonpolar bistable resistive switching behaviors of sol-gel derived bismuth titanate oxide (BTO) thin film are investigated in this study. The BTO thin film memory device without thermal treatment shows higher resistance ratio (similar to 10(4)) than the other annealed devices. The resistive switching behavior of the Pt/BTO/LNO/Pt device is reproducible and can be traced over 100 times. Both low resistance state (ON-state) and high resistance state (OFF-state) are stable over 10(4) s under 0.3 V voltage stress at room temperature (RT) and 85 degrees C. The retention behaviors of both memory states in the Pt/BTO/LNO/Pt device are very stable over 2 x 10(6) s at RT and 85 degrees C, showing that the BTO thin film memory device is a good candidate for nonvolatile memory application
Robust unipolar resistive switching of Co nano-dots embedded ZrO(2) thin film memories and their switching mechanism
(2012-01-01)
Wu, Ming-Chi
;
Wu, Tsung-Han
;
Tseng, Tseung-Yuen
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The preparation and electrical properties of Ti/Co Embedded (Co-E) ZrO(2)/Pt resistive switching memories are investigated. The Co nano-dots are formed in ZrO(2) thin film after the memory device is annealed at 600 degrees C in N(2) ambient for 60 s without any chemical reaction between Co and ZrO(2), which is confirmed from the transmission electron microscopy, energy dispersive X-ray analyzer, and X-ray photoelectron spectroscopy observations. The devices exhibit low forming voltage of 1.5 similar to 2.8V and robust negative bias unipolar resistive switching behaviors with small negative set voltage of -1.1 similar to-1.6 V. A physical model based on a filament mechanism is employed to explain the switching behaviors. It has a high potential for ultra high density nonvolatile memory applications. (C) 2012 American Institute of Physics. [doi: 10.1063/1.3674322]
Robust unipolar resistive switching of Co nano-dots embedded ZrO2 thin film memories and their switching mechanism
(2012-01-01)
Wu, Ming-Chi
;
Wu, Tsung-Han
;
Tseng, Tseung-Yuen
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The preparation and electrical properties of Ti/Co Embedded (Co-E) ZrO2/Pt resistive switching memories are investigated. The Co nano-dots are formed in ZrO2 thin film after the memory device is annealed at 600 degrees C in N-2 ambient for 60 s without any chemical reaction between Co and ZrO2, which is confirmed from the transmission electron microscopy, energy dispersive X-ray analyzer, and X-ray photoelectron spectroscopy observations. The devices exhibit low forming voltage of 1.5 similar to 2.8V and robust negative bias unipolar resistive switching behaviors with small negative set voltage of -1.1 similar to-1.6 V. A physical model based on a filament mechanism is employed to explain the switching behaviors. It has a high potential for ultra high density nonvolatile memory applications. (C) 2012 American Institute of Physics. [doi: 10.1063/1.3674322]