Browsing by Author "Chen, Li-Hui"

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Analysis of abnormal transconductance in body-tied partially-depleted silicon-on-insulator n-MOSFETs
(2017-12-31)
Lin, Chien-Yu
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Chang, Ting-Chang
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Liu, Kuan-Ju
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Chen, Li-Hui
;
Chen, Ching-En
This research investigates the mechanism of abnormal transconductance (Gm) and abnormal charge pumping current (I-CP) in body-tied partially-depleted silicon-on-insulator n-channel metal-oxide-semiconductor field effect transistors. The I-CP second hump region increases with channel length, yet is not affected by channel width. The cross-sectional view of the L-gate structure along the width direction demonstrates that a part of the poly gate area near the body contact is covered by a P+ implant, inducing a parasitic channel under the P+ poly gate. This parasitic channel leads to the abnormal Gm and I-CP hump, and such mechanism is further verified by body floating devices.
Analysis of Contrasting Degradation Behaviors in Channel and Drift Regions Under Hot Carrier Stress in PDSOI LD N-Channel MOSFETs
(2017-06-01)
Lin, Chien-Yu
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Chang, Ting-Chang
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Liu, Kuan-Ju
;
Chen, Li-Hui
;
Tsai, Jyun-Yu
This letter studies the effects of hot carrier stress (HCS) in laterally diffused silicon-on-insulator n-channel metal-oxide-semiconductor field-effect transistors. After HCS, threshold voltage and subthreshold swing degrade, while the ON-state current exhibits degradation after an abnormal spike due to hole trapping in the resistprotective oxide. Impact ionization simulation shows that low doping concentrations in the drift region cause a severe Kirk effect under HCS and more severe degradation at higher gate voltages. However, degradation in the channel contrasts with the simulation result, which suggests an additional mechanism. Variable temperature HCS confirms that channel degradation is instead dominated by temperature.
Drain-Induced-Barrier-Lowing-Like Effect Induced by Oxygen-Vacancy in Scaling-Down via-Contact Type Amorphous InGaZnO Thin-Film Transistors
(2018-01-01)
Yang, Chung-I.
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Chang, Ting-Chang
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Liao, Po-Yung
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Chen, Li-Hui
;
Chen, Bo-Wei
This investigation considers a method to ameliorate drain induced barrier lowing behavior in amorphous-indium-gallium-zinc-oxide thin-film transistors. The Vth is found to shift negatively when increasing the ID-VG measurement condition VD from 0.1 to 15 V. The current-voltage curves show that this degradation is caused by the effective channel length (L-eff) being shorter than the mask channel length (L). Using the transmission line method to extract Leff, we discover that the degradation will be completely suppressed by an annealing treatment. As a result, the degradation mechanism of shorter channel length a-IGZO thin film transistors is due to oxygen-vacancies which are located between the channel and the source/drain junction.
Fast-IV Measurement Investigation of the Role of TiN Gate Nitrogen Concentration on Bulk Traps in HfO2 Layer in p-MOSFETs
(2017-06-01)
Lu, Ying-Hsin
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Chang, Ting-Chang
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Liao, Jih-Chien
;
Chen, Li-Hui
;
Lin, Yu-Shan
This letter investigates the role of the TiN gate's nitrogen concentration on bulk traps in the HfO2 layer in p-MOSFETs using fast I-V measurement. During negative bias temperature instability, the holes trapped in the HfO2 layer will induce Vth degradation. The fast I-V double sweep confirms the holes are trapped in process-related pre-existing defects. These defects are interstitial-type, influenced by the nitrogen in the TiN gate diffusing to the HfO2 layer when the device undergoes thermal annealing. Moreover, these nitrogen interstitials increase with increasing TiN gate nitrogen concentration, which induces more holes being trapped in the HfO2 layer.
Impact of repeated uniaxial mechanical strain on flexible a-IGZO thin film transistors with symmetric and asymmetric structures
(2017-06-26)
Liao, Po-Yung
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Chang, Ting-Chang
;
Su, Wan-Ching
;
Chen, Bo-Wei
;
Chen, Li-Hui
This letter investigates repeated uniaxial mechanical stress-induced degradation behavior in flexible amorphous In-Ga-Zn-O thin-film transistors (TFTs) of different geometric structures. Two types of via-contact structure TFTs are investigated: symmetrical and UI structure (TFTs with Iand U-shaped asymmetric electrodes). After repeated mechanical stress, I-V curves for the symmetrical structure show a significant negative threshold voltage (VT) shift, due to mechanical stress-induced oxygen vacancy generation. However, degradation in the UI structure TFTs after stress is a negative VT shift along with the parasitic transistor characteristic in the forward-operation mode, with this hump not evident in the reverse-operation mode. This asymmetrical degradation is clarified by the mechanical strain simulation of the UI TFTs. Published by AIP Publishing.
The effect of device electrode geometry on performance after hot-carrier stress in amorphous In-Ga-Zn-O thin film transistors with different via-contact structures
(2017-05-15)
Liao, Po-Yung
;
Chang, Ting-Chang
;
Chen, Yu-Jia
;
Su, Wan-Ching
;
Chen, Bo-Wei
In this letter, the effects of hot carriers on amorphous In-Ga-Zn-O thin film transistors (TFTs) of different geometric structures were investigated. Three types of via-contact structure TFTs are used in this experiment, defined as source-drain large (SD large), source-drain normal (SD normal), and fork-shaped. After hot-carrier stress, the I-V curves of both SD normal and fork-shaped TFTs with U-shaped drains show a threshold voltage shift along with the parasitic transistor characteristic in the reverse-operation mode. Asymmetrical degradation is exhibited in an ISE-TCAD simulation of the electric field, which shows the distribution of hot electrons injected into the etch-stop layer below the redundant drain electrode. Published by AIP Publishing.