Browsing by Author "Tseng, Tseung-Yuen"

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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
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Ho, Yung-Han
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Lee, Ming-Hsiu
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Wang, Chao-Hung
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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 comprehensive study of bipolar operation in resistive switching memory devices
(2016-06)
Berco, Dan
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Tseng, Tseung-Yuen
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
The authors present a new numerical analysis method to investigate the conduction filament dynamics of a resistive switching nonvolatile metal-insulator-metal structured memory device. This comprehensive method, utilizing the Gibbs free energy criteria as a leading indicator and allowing simulation of all resistive memory operational phases (forming, set and reset), is presented for the first time. The formation and rupture of an oxygen vacancies based conduction filament are simulated to demonstrate a cycle of operation in a hafnium oxide based resistive forming layer. Starting from a random initial distribution of defect states, on to a formed conduction filament and ending in a ruptured state. Detailed plots of the physical parameters within the resistive layer are provided to gain deeper understanding of the conduction filament kinetics and introduce the concept of "hot spots", referring to random localized initial agglomeration of oxygen vacancies in which temperature surges is favored and contribute to initiate the conductive filament formation. By basing the method on well known thermodynamic properties and the Metropolis algorithm, simulation reliability and efficiency are obtained. The presented results confirm previously published data demonstrating the switching characteristics of hafnium based resistive random access memory.
A high performance transparent resistive switching memory made from ZrO2/AlON bilayer structure
(2016-04-11)
Tsai, Tsung-Ling
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Chang, Hsiang-Yu
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Lou, Jesse Jen-Chung
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Tseng, Tseung-Yuen
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電子工程學系及電子研究所
In this study, the switching properties of an indium tin oxide (ITO)/zirconium oxide (ZrO2)/ITO single layer device and those of a device with an aluminum oxynitride (AlON) layer were investigated. The devices with highly transparent characteristics were fabricated. Compared with the ITO/ZrO2/ITO single layer device, the ITO/ZrO2/AlON/ITO bilayer device exhibited a larger ON/OFF ratio, higher endurance performance, and superior retention properties by using a simple two-step forming process. These substantial improvements in the resistive switching properties were attributed to the minimized influence of oxygen migration through the ITO top electrode (TE), which can be realized by forming an asymmetrical conductive filament with the weakest part at the ZrO2/AlON interface. Therefore, in the ITO/ZrO2/AlON/ITO bilayer device, the regions where conductive filament formation and rupture occur can be effectively moved from the TE interface to the interior of the device. Published by AIP Publishing.
A Method to Determine the Located Region of Lateral Trap Position by Analysis of Three-Level Random Telegraph Signals in n-MOSFETs
(2015-01-01)
Chen, Ching-En
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Chang, Ting-Chang
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You, Bo
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Tsai, Jyun-Yu
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Lo, Wen-Hung
This paper introduces a method to determine the located region of trap position by the analysis of three-level random telegraph signal (RTS) in partially-depleted silicon-on-insulator n-channel metal-oxide-semiconductor field-effect-transistors. For the cases of two traps, the average time at the 2nd level ((12)) is composed of average emission time of one trap and average capture time of the other. Comparison and analysis of (tau(2)) curves varying with gate voltage in RTS measurements with and without interchanged source/drain can clarify the located regions of the two traps. Moreover, the simplified equations are also considered and used to confirm the trap positions. (C) 2015 The Electrochemical Society. All rights reserved.
A new redox phloroglucinol additive incorporated gel polymer electrolyte for flexible symmetrical solid-state supercapacitors
(2019-06-01)
Phuoc-Anh Le
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Van-Truong Nguyen
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Yen, Po-Jen
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Tseng, Tseung-Yuen
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Wei, Kung-Hwa
We reported a new and environmentally friendly phloroglucinol additive incorporated polyvinyl alcohol-LiClO4 gel polymer electrolyte for flexible symmetrical solid-state supercapacitors. The incorporation of 10 wt% phloroglucinol into PVA-LiClO4 gel polymer electrolytes results in much higher specific capacitance (114 F g(-1)) than that without phloroglucinol (60 F g(-1)), an increase of 90%, because of the redox reaction of phloroglucinol in the system. We used the PVA-LiClO4 with 10 wt% phloroglucinol as a gel polymer electrolyte in combination with nitrogen-doped graphene nanosheet-based electrodes as the anode and cathode to fabricate a symmetrical solid-state supercapacitor. The fabricated supercapacitor involving the phloroglucinol redox additive has an energy density of 2.3 W h kg(-1) at a power density of 150 W kg(-1), which is higher than the one without a redox additive (1.9 W h kg(-1) at a power density of 150 W kg(-1)). Moreover, the supercapacitor involving the redox additive has good stability; its capacitance remains at up to similar to 94% after 5000 charge/discharge cycles.
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
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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.
A numerical analysis of progressive and abrupt reset in conductive bridging RRAM
(2016-06)
Berco, Dan
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Tseng, Tseung-Yuen
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
The authors investigate the conduction filament (CF) properties of a Cu- based conductive bridging resistive memory device by implementing a numerical simulation of the low and high resistive states, starting from a random initial distribution of oxygen vacancies (OV) defects states in the resistive switching layer (RSL) to a formed CF and ending in a ruptured state. A calculation approach which accounts for both the statistical nature of the system and the synergetic effect of OV and Cu species on the overall conductance is presented. By defining a disorder parameter, the correlation between the OV initial distribution and the CF reset behavior is analyzed. A dependence of the reset transition, being either abrupt or progressive, on the physical shape of the CF which in turn is affected by this disorder is shown to exist based on the simulation results.
A numerical study of forming voltage and switching polarity dependence on Ti top electrode thickness in Zr RRAM
(2016-06)
Berco, Dan
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Tseng, Tseung-Yuen
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
The authors investigate the conduction filament (CF) formation voltage and reset polarity dependence of a Ti/Zr/Pt resistive switching memory device on the Ti top electrode (TE) thickness by means of numerical simulation. A calculation method which accounts for both the initial statistical nature of the resistive switching layer (RSL) and the interaction of oxygen vacancies with oxygen species (O) on the overall conductance is used. The results show a correlation between the TE thickness and the density profile of O species both along the RSL-TE interface and within the TE, and indentify the causes for the previously observed not yet fully comprehended TE thickness dependent functionality of this device. The authors demonstrate that accumulation and reduction of O, during forming, result in a charged interfacial layer which decreases the effective oxide thickness and determines the forming voltage and switching polarity. In addition, local temperature profiles within the CF during forming promote O diffusion into the TE material which reduces the local conductivity and affects the forming voltage magnitude as well. In addition the authors provide forming and reset calculations for TE thicknesses of 5, 20 and 40 nm which are in good agreement with published experimental data.
A numerical study of multi filament formation in metal-ion based CBRAM
(2016-02-01)
Berco, Dan
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Tseng, Tseung-Yuen
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
This study investigates the underlying mechanisms of multiple conductive filaments (CF) creation in metal-ion based conductive bridge RRAM (CBRAM) by using the Metropolis Monte Carlo algorithm and suggests a possible explanation for this phenomenon. The simulation method is demonstrated over a Cu/HfO2 structure, starting from a random initial distribution of oxygen vacancies (OV) defects in the resistive switching layer, to a formed CF and ending in a ruptured state. the results indicate that "Hot Spots" (HS), where agglomeration of OV trap like states for electron hopping based conduction induce local heating, create favorable energy conditions to attract diffused metal species originating from the top electrode. While HS may be created and annihilated by random OV generation and recombination processes, the precipitated metal forms a stem out of which a CF could evolve. The CF stem's final growth stage is mainly driven by drift and diffusion. This process may lead to the formation of one or more CFs as a function of the forming bias voltage. This bias dependence is demonstrated over a large range, where the creation of a single, double and multiple CFs are shown. In addition, the reset process of the multi CF device is presented, and the experimentally observed, step like, gradual CBRAM reset is verified. The simulated results are in good agreement with experimental data and promote the idea that OV defect engineering may be used to improve CBRAM performance. (C) 2016 Author(s).
A stochastic simulation method for the assessment of resistive random access memory retention reliability
(2015-12-21)
Berco, Dan
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Tseng, Tseung-Yuen
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電子工程學系及電子研究所
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Department of Electronics Engineering and Institute of Electronics
This study presents an evaluation method for resistive random access memory retention reliability based on the Metropolis Monte Carlo algorithm and Gibbs free energy. The method, which does not rely on a time evolution, provides an extremely efficient way to compare the relative retention properties of metal-insulator-metal structures. It requires a small number of iterations and may be used for statistical analysis. The presented approach is used to compare the relative robustness of a single layer ZrO2 device with a double layer ZnO/ZrO2 one, and obtain results which are in good agreement with experimental data. (C) 2015 AIP Publishing LLC.
A stochastic simulation method for the assessment of resistive random access memory retention reliability
(2015-12-21)
Berco, Dan
;
Tseng, Tseung-Yuen
;
電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
This study presents an evaluation method for resistive random access memory retention reliability based on the Metropolis Monte Carlo algorithm and Gibbs free energy. The method, which does not rely on a time evolution, provides an extremely efficient way to compare the relative retention properties of metal-insulator-metal structures. It requires a small number of iterations and may be used for statistical analysis. The presented approach is used to compare the relative robustness of a single layer ZrO2 device with a double layer ZnO/ZrO2 one, and obtain results which are in good agreement with experimental data. (C) 2015 AIP Publishing LLC.
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
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Jang, Wen-Yueh
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Lin, Chen-Hsi
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Tseng, Tseung-Yuen
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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.
Abnormal threshold voltage shift under hot carrier stress in Ti1-xNx/HfO2 p-channel metal-oxide-semiconductor field-effect transistors
(2013-09-28)
Tsai, Jyun-Yu
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Chang, Ting-Chang
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Lo, Wen-Hung
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Ho, Szu-Han
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Chen, Ching-En
This work investigates the channel hot carrier (CHC) effect in HfO2/Ti1-xNx p-channel metal oxide semiconductor field effect transistors (p-MOSFETs). Generally, the subthreshold swing (S. S.) should increase during CHC stress (CHCS), since interface states will be generated near the drain side under high electric field due to drain voltage (V-d). However, our experimental data indicate that S. S. has no evident change under CHCS, but threshold voltage (V-th) shifts positively. This result can be attributed to hot carrier injected into high-k dielectric near the drain side. Meanwhile, it is surprising that such V-th degradation is not observed in the saturation region during stress. Therefore, drain-induced-barrier-lowering (DIBL) as a result of CHC-induced electron trapping is proposed to explain the different V-th behaviors in the linear and saturation regions. Additionally, the influence of different nitrogen concentrations in HfO2/Ti1-xNx p-MOSFETs on CHCS is also investigated in this work. Since nitrogen diffuses to SiO2/Si interface induced pre-N-it occurring to degrades channel mobility during the annealing process, a device with more nitrogen shows slightly less impact ionization, leading to insignificant charge trapping-induced DIBL behavior. (C) 2013 AIP Publishing LLC.
An electrophoretic-deposited low-cost carbon nanotube (CNT) thermophotovoltaic emitter
(2018-01-01)
Lin, Albert
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Parashar, Parag
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Yang, Chien-Chih
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Hao-MingChou
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Lin, Yi-Shiuan
We use electrophoresis technique to deposit a low-cost carbon nanotube (CNT) film on tantalum (Ta) for thermophotovoltaic (TPV) emitters. The initial thermal measurement of the EPD-CNT film from 200 degrees C-800 degrees C is conducted. The elimination of high-temperature CVD deposition facilitates the commercialization of TPV devices. The UV-VIS-NIR spectrum and high-temperature FTIR measurement are reported to assess the feasibility of EPD-CNT as a TPV emitter candidate. The planarized nature of the proposed emitter can be easily integrated with dielectric multi-layer filter for spectral shaping depending on applications.
Analysis of an anomalous hump in gate current after dynamic negative bias stress in HfxZr1-xO2/metal gate p-channel metal-oxide-semiconductor field-effect transistors
(1970-01-01)
Ho, Szu-Han
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Chang, Ting-Chang
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Wu, Chi-Wei
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Lo, Wen-Hung
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Chen, Ching-En
"This letter investigates a hump in gate current after dynamic negative bias stress (NBS) in HfxZr1-xO2/metal gate p-channel metal-oxide-semiconductor field-effect transistors. By measuring gate current under initial through body floating and source/drain floating, it shows that hole current flows from source/drain. The fitting of gate current-gate voltage characteristic curve demonstrates that Frenkel-Poole mechanism dominates the conduction. Next, by fitting the gate current after dynamic NBS, in the order of Frenkel-Poole then tunneling, the Frenkel-Poole mechanism can be confirmed. These phenomena can be attributed to hole trapping in high-k bulk and the electric field formula Ehigh-k epsilon(high-k) = Q + E-sio2 epsilon(sio2). (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4739525]"
Analysis of anomalous traps measured by charge pumping technique in HfO2/metal gate n-channel metal-oxide-semiconductor field-effect transistors
(2012-12-03)
Ho, Szu-Han
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Chang, Ting-Chang
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Lu, Ying-shin
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Lo, Wen-Hung
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Chen, Ching-En
This letter investigates anomalous traps measured by charge pumping technique in high voltage in HfO2/metal gate n-channel metal-oxide-semiconductor field-effect transistors. N-V-high level characteristic curves with different duty ratios indicate that the electron discharge time dominates the value of N for extra traps. By fitting ln (N (t(base level) = 2.5 mu s)-N (t(base level)))-Delta t(base level) at different temperatures and computing the equation t = tau(0) exp (alpha(e,SiO2)d(SiO2) + alpha(e,HfO2)d(HfO2,trap)), results show that these extra traps measured by the charge pumping technique at high voltage can be attributed to high-k bulk shallow traps. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4769444]
Analysis of Oxide Trap Characteristics by Random Telegraph Signals in nMOSFETs With HfO2-Based Gate Dielectrics
(2016-04)
Chen, Ching-En
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Chang, Ting-Chang
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You, Bo
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Tsai, Jyun-Yu
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Lo, Wen-Hung
This letter investigates the oxide trap properties in n-channel metal-oxide-semiconductor field-effect transistors with HfO2 and Hf(1-x)ZrxO(2)/metal gate-stacks by an analysis of random telegraph signals. According to the multiphonon emission theory, the extracted relaxation energies show gate voltage dependence in devices with HfO2-based stacks. This dependence results from the different strengths of vibrations of the nearest neighbor Hf atoms of the oxygen vacancy in the immediate vicinity of the oxide trap. Furthermore, this dependence also induces an abnormal gate voltage dependence in terms of the activation energy required for electron capture. These results are confirmed by comparisons between two HfO2-based devices (HfO2 and Hf(1-x)ZrxO(2)).
Anomalous Gate Current Hump after Dynamic Negative Bias Stress and Negative-Bias Temperature-Instability in p-MOSFETs with HfxZr1-xO2 and HfO2/Metal Gate Stacks
(2013)
Ho, Szu-Han
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Chang, Ting-Chang
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Wu, Chi-Wei
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Lo, Wen-Hung
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Chen, Ching-En
In this study, the authors investigated an anomalous gate current hump after dynamic negative bias stress (NBS) and negative-bias temperature-instability (NBTI) in HfxZr1-xO2 and HfO2/metal gate p-channel metal-oxide-semiconductor field-effect transistors. This result is attributed to hole trapping in high-k bulk. Measuring gate current under initial through body floating and source/drain floating conditions indicates that holes flow from source/drain to gate. The fitting of the gate current-gate voltage characteristic curve demonstrates that Frenkel-Poole mechanism dominates the conduction under initial. Next, fitting the gate current after dynamic NBS and NBTI indicates Frenkel-Poole then tunneling mechanisms, finally returning to the Frenkel-Poole mechanism. These phenomena can be attributed to hole trapping in high-k bulk and the formula Ehigh-k epsilon(high-k) = Q + E-sio2 epsilon(sio2). To further understand the gate current hump, both Zr-undoped and 8 similar to 10% Zr-doped in high-k bulk devices were used for comparisons. These results indicate that initial gate current is also a significant factor in generating the anomalous gate current hump, and all results obey the hump generation condition of J(Tunneling) << J(Frenkel-Poole). (C) 2013 The Electrochemical Society. All rights reserved.
Bias-induced oxygen adsorption in zinc tin oxide thin film transistors under dynamic stress
(2010-06-28)
Chen, Yu-Chun
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Chang, Ting-Chang
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Li, Hung-Wei
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Chen, Shih-Ching
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Lu, Jin
This study investigates the effects of bias-induced oxygen adsorption on the electrical characteristic instability of zinc tin oxide thin film transistors in different ambient oxygen partial pressures. When oxygen pressure is largest, the threshold voltages showed the quickest increase but the slowest recovery during the stress phase and recovery phase, respectively. This finding corresponds to the charge trapping time constant and recovery time constant, which are extracted by fitting the stretched-exponential equation and which exhibit a relationship with oxygen pressure. We suggest that the gate bias reduces the activation energy of oxygen adsorption during gate bias stress. (C) 2010 American Institute of Physics. [doi: 10.1063/1.3457996]
Boosting Ge-epi N-well Mobility with Sn Implantation and P-well Mobility with Cluster-C Implantation
(2018-01-01)
Borland, John
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Chaung, Shang-Shiun
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Tseng, Tseung-Yuen
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Lee, Yao-Jen
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Joshi, Abhijeet
We investigated the effects of Sn, Si and cluster-C implantation into both P-well and N-well doped regions of 100nm Ge-epilayer on Si wafers after RTA annealing. For the P-well case a 7.3x increase in Hall bulk mobility to 3384cm(2)/Vs with cluster-C implant and for the N-well case a 4.6x increase in Hall bulk mobility to 2062cm(2)/Vs with Sn implant. Measuring layer mobility depth profiles shows mobility in the top 10-20nm of the surface can be up to 6000cm(2)/Vs for N-well with Sn implant and >10,000cm(2)/Vs for P-well with Sn implant.