Browsing by Author "Teng, TH"

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Degradation of passivated and non-passivated N-channel low-temperature polycrystalline silicon TFTs prepared by excimer laser processing
(2002-08-01)
Teng, TH
;
Huang, CY
;
Chang, TK
;
Lin, CW
;
Cheng, LJ
The instability mechanisms of passivated and non-passivated low-temperature polycrystalline silicon thin film transistors (LTPS TFTs) under various bias stress conditions have been investigated. Irrespective of plasma treatment, the degradation was more severe under negative gate bias stress than that under positive gate bias stress. This could be due to Fowler-Nordheim tunneling electron induced impact ionization. For hot carrier stress, TFTs with NH3 plasma treatment degraded more severely than those without plasma treatment. This might be attributed to collapsing of weak Si-H bonds in NH3-plasma passivated devices. For the high current stress, it showed the opposite results against hot carrier stress. (C) 2002 Elsevier Science Ltd. All rights reserved.
Effect of temperature and illumination on the instability of a-Si : H thin-film transistors under AC gate bias stress
(2001-04-01)
Huang, CY
;
Teng, TH
;
Yang, CJ
;
Tseng, CH
;
Cheng, HC
This work investigates the temperature and illumination effects on the a-SM thin-film transistors (a-SiH TFTs) under AC gate bias stress to find the larger threshold voltage shift and subthreshold swing change for the bias-temperature-stress (BTS) and bias-illumination-stress (BIS). Excess carriers from thermal-generation electron-hole pairs or photoexcited electron-hole pairs may significantly influence the instability of a-SM TFTs during bias stress. The instability mechanisms originate from the carrier-induced defect Creation enhanced by thermal generation in the BTS case and also emphasized by photoexcitation for the BIS case. Both stress conditions will induce a larger threshold voltage shift and higher cutoff frequency than those for simple bias stresses.
Effect of TiN treated by rapid thermal annealing on properties of BST capacitors prepared by RF magnetron co-sputter system at low substrate temperature
(2000)
Teng, TH
;
Hwang, CC
;
Lai, MJ
;
Huang, SC
;
Chen, JS
In this work, (Ba0.7Sr0.3)TiO3 thin films on Pt/TiN/Ti/Si substrate were deposited by an RF magnetron co-sputter system at 300 degrees C in an Ar+O-2 mixed ambient. In the integration of BST capacitors, the diffusion barrier (TiN) under bottom electrodes is one of the key issues. To obtain a stable and excellent diffusion barrier against inter-diffusion between Pt and Si, as well as against being oxidized during BST deposition, TiN was treated by a rapid thermal annealing (RTA) process. Experimental results indicated that proper RTA treatments resulted in a superior TiN barrier layer. In addition, low substrate temperature during BST deposition suppressed the phenomena of inter-diffusion and barrier oxidation. Furthermore, Pt hillocking, another problem during BST deposition because of high thermal budget, was also solved by reducing substrate temperature during BST deposition. The MIM (Pt/BST/Pt) structure was used in the experiments for electrical properties measurement. High dielectric constant (epsilon (r)=300), low leakage current (1.5x10(-8) A/cm(2)) under 0.1MV/cm, and 10 year lifetime under 1.6MV/cm were achieved with an Ar+O-2 mixed ambient at a low substrate temperature (300 degrees C).
Study on dopant activation of phosphorous implanted polycrystalline silicon thin films by KrF excimer laser annealing
(2002-08-01)
Tseng, CH
;
Lin, CW
;
Teng, TH
;
Chang, TK
;
Cheng, HC
The KrF excimer laser annealing of phosphorous implanted polycrystalline silicon (poly-Si) films had been investigated completely. Resistors were fabricated to measure sheet resistance of poly-Si film. The interference effect, heat absorption of capping oxide as well as transformation of poly-Si grain size during laser annealing were reported. Depending on the carrier concentrations, poly-Si exhibits different sheet resistance behavior when the excimer laser fluence is higher than the full-melt threshold fluence. The sheet resistance of poly-Si film has an abnormal increase from 5 x 10(4) to 4 x 10(6) Q/square when the excimer laser energy is higher than full-melt threshold energy. (C) 2002 Elsevier Science Ltd. All rights reserved.
The instability mechanisms of hydrogenated amorphous silicon thin film transistors under AC bias stress
(2000-07-01)
Huang, CY
;
Teng, TH
;
Tsai, JW
;
Cheng, HC
;
電子工程學系及電子研究所
Hydrogenated amorphous silicon (a-Si:H) thin-film transistors (TFTs) with silicon nitride (SiNx) gates have been stressed under various AC biases to investigate the instability mechanisms. The state creation is dominant at low stress voltage although the charge trapping also occurs in SiNx gates, and such cases have also been found under the DC bias stress. In addition, the degradations of a-Si:H TFTs are found to be independent of the AC frequency for the positive polarity but show frequency dependence for the negative polarity due to the RC effect. Furthermore, the threshold voltage shift is associated with the duty ratio due to the accumulation of stress time. Finally, the degradation of the a-Si:H TFTs under bipolar AC bias stress is also introduced. It is found that the instability mechanisms of devices are composed of different charge compensations in SiNx and redistributions of defect states in the a-Si:H layer.
Turnaround phenomenon of threshold voltage shifts in amorphous silicon thin film transistors under negative bias stress
(2000-10-01)
Huang, CY
;
Tsai, JW
;
Teng, TH
;
Yang, CJ
;
Cheng, HC
The turnaround phenomenon of threshold voltage shifts is investigated in thin film transistors (TFTs) with different defect densities of hydrogenated amorphous silicon (a-Si:H) films and compositions of SiNx. It was found that TFTs with high-defect-density a-Si:H films and N-rich SiNx gate exhibit the turnaround phenomenon while TFTs with other conditions of a-Si:H and SiNx films do not. Results reveal that the turnaround phenomenon is greatly influenced by charge traps in SiNx and state creation in the a-Si:H layer. When state creation is dominant at low bias stress, the turnaround phenomenon occurs. In contrast, if charge trapping is dominant at low bias stress, the turnaround phenomenon does not occur.