Browsing by Author "Hung, Ya-Chi"

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Abnormal Subthreshold Leakage Current at High Temperature in InGaZnO Thin-Film Transistors
(2012-04-01)
Chang, Geng-Wei
;
Chang, Ting-Chang
;
Jhu, Jhe-Ciou
;
Tsai, Tsung-Ming
;
Syu, Yong-En
Abnormal subthreshold leakage current is observed at high temperature in amorphous InGaZnO thin-film transistors. The transfer curve exhibits an apparent subthreshold current stretch-out phenomenon that becomes more serious with increasing temperatures. The negative bias temperature instability experiment has been used to prove high-temperature-induced hole generation. Furthermore, the transfer characteristics with different drain voltages have been also used to confirm the status of hole accumulation. These pieces of evidence clearly defined the stretch-out phenomenon, which is caused by thermal-induced hole generation and accumulation at the source region that leads to source-side barrier lowering.
An Electronic Synapse Device Based on Solid Electrolyte Resistive Random Access Memory
(2015-08-01)
Zhang, Wei
;
Hu, Ying
;
Chang, Ting-Chang
;
Chang, Kuan-Chang
;
Tsai, Tsung-Ming
The multilevel capability of solid electrolyte resistive random access memory (RRAM) with a Pt/GeSO/TiN structure was explored for potential use as a synapse device. By varying the cutoff voltage during the dc I-V cycles or the ac pulse programming voltage amplitudes, continuous multilevel conductance states were obtained. The reference Pt/GeO/TiN RRAM was fabricated to certify the multilevel capability and was due to the character of the GeS solid electrolyte. Finally, the property of gradual conductance states was exploited to demonstrate spike-timing-dependent plasticity learning, which suggests device\'s potential for use as an electronic synapse device for neuromorphic systems.
Charge trapping induced frequency-dependence degradation in n-MOSFETs with high-k/metal gate stacks
(2011-12-30)
Dai, Chih-Hao
;
Chang, Ting-Chang
;
Chu, Ann-Kuo
;
Kuo, Yuan-Jui
;
Hung, Ya-Chi
This letter investigates the reliability issues of HfO(2)/Ti(1-x)N(x) metal-oxide-semiconductor field effect transistor in terms of static and dynamic stress. The results indicate threshold voltage (V(th)) instability under dynamic stress is more serious than that under static stress, owning to transient charge trapping within high-k dielectric. Capacitance-voltage techniques verified that electron trapping under dynamic stress was located in high-k dielectric near the source/drain (S/D) overlap region, rather than the overall dielectric. Furthermore, the V(th) shift clearly increases with an increase in dynamic stress operation frequency. This phenomenon can be attributed to the fact that electrons injecting to the S/D overlap region have insufficient time to de-trap from high-k dielectric. We further investigated the impact of different Ti(1-x)N(x) composition of metal-gate electrode on charge trapping characteristics, and observed that V(th) shift decreases significantly with an increase in the ratio of nitride. This is because the nitride atoms diffusing from the metal gate fill up oxygen vacancies and reduce the concentration of traps in high-k dielectric. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.
Effects of Varied Negative Stop Voltages on Current Self-Compliance in Indium Tin Oxide Resistance Random Access Memory
(2015-06-01)
Lin, Chih-Yang
;
Chang, Kuan-Chang
;
Chang, Ting-Chang
;
Tsai, Tsung-Ming
;
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.
Mechanism of Triple Ions Effect in GeSO Resistance Random Access Memory
(2015-06-01)
Zhang, Wei
;
Hu, Ying
;
Chang, Ting-Chang
;
Tsai, Tsung-Ming
;
Chang, Kuan-Chang
In this letter, a triple-ion redox reaction has been proposed and investigated in GeSO-based resistance random access memory. Continuous multiresistance states can be obtained by applying a series of increasing cutoff voltages in both set and reset processes. Using data retention tests, these multistates in the set and reset processes were confirmed to be stable. The conduction mechanism gradually changed during reset process from space charge limited current to Schottky emission. A triple-ion reaction model has been proposed to reveal the chemical reaction properties in the resistive switching process.
N2O plasma treatment suppressed temperature-dependent sub-threshold leakage current of amorphous indium-gallium-zinc-oxide thin film transistors
(2013-09-01)
Chang, Geng-Wei
;
Chang, Ting-Chang
;
Jhu, Jhe-Ciou
;
Tsai, Tsung-Ming
;
Syu, Yong-En
N2O plasma treatment suppressed the temperature-dependent sub-threshold leakage current of amorphous indium-gallium-zinc-oxide thin film transistors (a-IGZO TFTs). For untreated devices, the transfer curve exhibited abnormal electrical properties at high temperature. The abnormal electrical properties are explained by the energy band diagrams for both forward and reverse sweep. Above 400 K, holes can be generated from trap-assisted transition, and drift to the source side which induces source barrier lowering. The source side barrier lowering enhances electron injection from the source to channel and causes an apparent sub-threshold leakage current. This phenomenon, which is experimentally verified, only appears in the device without N2O plasma treatment, but not in the device with N2O plasma treatment. The results suggested that the density of states for a-IGZO with N2O plasma treatment is much lower than that without plasma treatment. (C) 2012 Elsevier B.V. All rights reserved.
Nitrogen Buffering Effect on Oxygen in Indium-Tin-Oxide-Capped Resistive Random Access Memory With NH3 Treatment
(2015-11-01)
Chen, Ji
;
Chang, Kuan-Chang
;
Chang, Ting-Chang
;
Tsai, Tsung-Ming
;
Pan, Chih-Hung
In this letter, we demonstrate the differing influences of a nitrogen buffering effect in both the switching layer and the indium-tin-oxide (ITO) electrode layer of resistive random access memory (RRAM) which has undergone an NH3 treatment. The nitrogen buffering effect in the switching layer cannot counteract the electric field force, leading to similar I-V characteristics compared with the ITO/Hf:SiO2/TiN control structure RRAM. The nitrogen in the ITO electrode layer, however, works as an oxygen buffer and makes it easier for the redox reaction to occur, leading to improvements in performance, such as concentrated voltages and better endurance.
Paraffin wax passivation layer improvements in electrical characteristics of bottom gate amorphous indium-gallium-zinc oxide thin-film transistors
(2011-12-30)
Chang, Geng-Wei
;
Chang, Ting-Chang
;
Syu, Yong-En
;
Tsai, Tsung-Ming
;
Chang, Kuan-Chang
In this research, paraffin wax is employed as the passivation layer of the bottom gate amorphous indium-gallium-zinc oxide thin-film transistors (a-IGZO TFTs), and it is formed by sol-gel process in the atmosphere. The high yield and low cost passivation layer of sol-gel process technology has attracted much attention for current flat-panel-display manufacturing. Comparing with passivation-free a-IGZO TFTs, passivated devices exhibit a superior stability against positive gate bias stress in different ambient gas, demonstrating that paraffin wax shows gas-resisting characteristics for a-IGZO TFTs application. Furthermore, light-induced stretch-out phenomenon for paraffin wax passivated device is suppressed. This superior stability of the passivated device was attributed to the reduced total density of states (DOS) including the interfacial and semiconductor bulk trap densities. (C) 2011 Elsevier B.V. All rights reserved.
Redox Reaction Switching Mechanism in RRAM Device With Pt/CoSiO(X)/TiN Structure
(2011-04-01)
Syu, Yong-En
;
Chang, Ting-Chang
;
Tsai, Tsung-Ming
;
Hung, Ya-Chi
;
Chang, Kuan-Chang
This letter investigates the resistive random access memory device characteristics and the physical mechanism of a device with a TiN/CoSiO(X)/Pt structure. In general, the mechanism is regarded as a redox reaction in the dielectric interface between the Ti electrode and the conductive filament. Furthermore, the switching voltage is correlated only with redox reaction potential. A designed circuit is used to accurately observe the resistance switching process with a pulse generator and an oscilloscope, which reveals that the switching process is related to both time and voltage. The constant switching energy demonstrates that the switching mechanism is the redox reaction.
Redox Reaction Switching Mechanism in RRAM Device With Pt/CoSiOX/TiN Structure
(2011-04-01)
Syu, Yong-En
;
Chang, Ting-Chang
;
Tsai, Tsung-Ming
;
Hung, Ya-Chi
;
Chang, Kuan-Chang
This letter investigates the resistive random access memory device characteristics and the physical mechanism of a device with a TiN/CoSiOX/Pt structure. In general, the mechanism is regarded as a redox reaction in the dielectric interface between the Ti electrode and the conductive filament. Furthermore, the switching voltage is correlated only with redox reaction potential. A designed circuit is used to accurately observe the resistance switching process with a pulse generator and an oscilloscope, which reveals that the switching process is related to both time and voltage. The constant switching energy demonstrates that the switching mechanism is the redox reaction.
Suppress temperature instability of InGaZnO thin film transistors by N2O plasma treatment, including thermal-induced hole trapping phenomenon under gate bias stress
(2012-04-30)
Chang, Geng-Wei
;
Chang, Ting-Chang
;
Jhu, Jhe-Ciou
;
Tsai, Tsung-Ming
;
Syu, Yong-En
An abnormal subthreshold leakage current is observed at high temperature, which causes a notable stretch-out phenomenon in amorphous InGaZnO thin film transistors (a-IGZO TFTs). This is due to trap-induced thermal-generated holes accumulating at the source region, which leads to barrier lowering on the source side and causes an apparent subthreshold leakage current. In order to obtain superior thermal stability performance of a-IGZO TFTs, conducting N2O plasma treatment on active layer was expected to avert defects generation during SiO2 deposition process. Reducing defects generation not only suppresses subthreshold current stretch-out phenomenon but also significantly improves the bias stress stability in a-IGZO TFTs at high temperature. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4709417]
Temperature-Dependent Instability of Bias Stress in InGaZnO Thin-Film Transistors
(2014-06-01)
Chang, Geng-Wei
;
Chang, Ting-Chang
;
Jhu, Jhe-Ciou
;
Tsai, Tsung-Ming
;
Chang, Kuan-Chang
The instability of the gate bias and drain bias stresses is observed at high temperature in amorphous InGaZnO thin-film transistors (a-IGZO TFTs). The transfer characteristics of a-IGZO TFTs at different temperatures are also investigated in this paper. The transfer curve exhibits an apparent subthreshold current stretchout phenomenon at high temperature. The stretchout phenomenon becomes more serious with the increase of the temperature. In addition, thermally induced holes are accumulated by the negative gate voltage and get trapped in the gate dielectric or at the dielectric/channel interface at high temperature. The negative threshold voltage shifts with stress time and this is because the trapped holes induce more electrons. For drain bias stress at high temperature, the transfer curve exhibits an apparent shift during drain bias stress at high temperature compared with the same at room temperature. At high temperature, thermally induced holes are trapped in the gate insulator, especially near the drain region. Capacitance-voltage measurements have been used to prove the nonuniform hole-trapping phenomenon. Furthermore, the simulation of the capacitance-voltage and current-voltage curves also have been applied to confirm the hole-trapping distribution. The obtained results clarify that the instability is caused by nonuniform hole-trapping phenomenon.