Browsing by Author "Tsai, Kou-Chiang"

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Improving electrical characteristics of Ta/Ta2O5/Ta capacitors using low-temperature inductively coupled N2O plasma annealing
(2007)
Tsai, Kou-Chiang
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Wu, Wen-Fa
;
Chao, Chuen-Guang
;
Wu, Chi-Chang
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材料科學與工程學系
The electrical characteristics of Ta/Ta2O5/Ta capacitors are improved by treatments with inductively coupled N2O plasma. A low-temperature (250 degrees C) and short (5 min) process was used to reduce the leakage current and improve the reliability. A low leakage current density (4.0x10(-10) A/cm(2) under 1 MV/cm), high breakdown field (4.2 MV/cm at 10(-6) A/cm(2)), and lifetime of over 10 years at 1.61 MV/cm is obtained for the Ta/Ta2O5/Ta capacitor with the inductively coupled N2O plasma treatment. The conduction mechanism of the leakage current in the Ta/Ta2O5/Ta capacitor is discussed using current-voltage analyses and shows that the leakage current of the Ta/Ta2O5/Ta capacitor is dominated by Schottky emission. N2O plasma treatment can effectively reduce oxygen vacancies and the surface roughness of the Ta2O5 film, inhibiting the conduction of the leakage current. (c) 2007 The Electrochemical Study.
Improving electrical properties and thermal stability of (Ba,Sr)TiO3 thin films on Cu(Mg) bottom electrodes
(2006-06-01)
Tsai, Kou-Chiang
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Wu, Wen-Fa
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Chao, Chuen-Guang
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Lee, Jain-Tsai
;
Shen, Shih-Wen
Cu(Mg) alloy films have replaced pure Cu as bottom electrodes for (Ba,Sr)TiO3 (BST) capacitors used in high-frequency devices. A combined BST/Cu(Mg) structure reduced the leakage current density to 3.0 x 10(-8) A/cm(2) at 1 MV/cm, and increased the breakdown field from 0.4 to 2.4 MV/cm at 10(-6) A/cm(2), from the corresponding values of the BST/Cu structure. High-quality characteristics probably follow the formation of a self-aligned MgO layer following the deposition of a Cu(Mg) alloy by annealing in an oxygen ambient, yielding an electrode with an excellent diffusion barrier and electrical characteristics, which is therefore effective in a BST thin-film capacitor. Additionally, the bias temperature stress and time-dependent dielectric breakdown in ambient nitrogen at an electric field of up to 2 V at temperatures between 100 and 200 degrees C were considered to accelerate Cu+ ion drift.
Influence of bias-temperature stressing on the electrical characteristics of SiOC : H film with Cu/TaN/Ta-gated capacitor
(2006-07-01)
Tsai, Kou-Chiang
;
Wu, Wen-Fa
;
Chao, Chuen-Guang
;
材料科學與工程學系
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Department of Materials Science and Engineering
Experiments on bias-temperature stressing, capacitance-voltage measurements, current-voltage characteristics, and time-dependent dielectric breakdown were performed to evaluate the reliability of Cu and low-k SiOC:H integration. A high leakage current of similar to 8 X 10(-10) to 2 X 10(-8) A/cm(2) at 1 MV/cm in SiOC:H dielectrics in a Cu-gated capacitor, and a lower 2 X 10(-10) to 5 X 10(-10) A/cm(2) at 1 MV/cm in a Cu/TaN/Ta-gated capacitor, were observed at evaluated temperatures. The drift mobility of the Cu ions in the Cu/TaN/Ta-gated capacitor was lower than that in a Cu-gated capacitor. A physical model was developed to explain the observed kinetics of Cu+ ions that drift in Cu-gated and Cu/TaN/Ta-gated capacitors. The electric field in the Cu-gated MIS capacitor in the cathode region is believed to be increased by the accumulation of positive Cu+ ions, which determines the breakdown acceleration. Good Cu, ions drift barrier layers are required as reliable interconnects using thin TaN and Ta layers. Additionally, Schottky emission dominates at low electric fields, E < 1.25 MV/cm, and Poole-Frenkel emission dominates at high fields, E > 1.5 MV/cm.
Influences of Ti, TiN, Ta and TaN layers on integration of low-k SiOC : H and Cu
(2007-07-15)
Tsai, Kou-Chiang
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Wu, Wen-Fa
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Chao, Chuen-Guang
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Hsu, Jwo-Lun
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Chiang, Chiu-Fen
The interactions between low-k material hydrogenated silicon oxycarbide (SiOC:H) and barrier layers, Ta, TaN, physical-vapor deposition (PVD) and chemical-vapor deposition (CVD) Ti and TiN, have been investigated. The results show these barriers except TaN can react with SiOC:H at evaluated temperature. Furthermore, significant interactions of carbon and oxygen due to the degradation of the SiOC:H films upon annealing exist for all barrier/SiOC:H structures. The CVD-TiN structure can retard the hydrogen out-diffusion, while PVD-TiN structure induces the H out-diffusion from the SiOC:H films. By studying flat band voltage shift in C-V tests, it is demonstrated that Cu+ ions drift into SiOC:H under electric field at elevated temperatures. A thin layer of TaN is proven to be good Cu drift barrier layer with SiOC:H dielectrics. (c) 2007 Elsevier B.V. All rights reserved.
Repairing of etching-induced damage of high-k Ba0.5Sr0.5TiO3 thin films by oxygen surface plasma treatment
(2006-06-01)
Tsai, Kou-Chiang
;
Wu, Wen-Fa
;
Chao, Chuen-Guang
;
Lee, Jain-Tsai
;
Hsu, Jwo-Lun
Ba0.5Sr0.5TiO3 (BST) thin films were patterned for fabricating BST capacitors in a helicon-wave plasma system. The optimization conditions were an Ar (80%)/Cl-2 (20%) gas mixture with a helicon-wave plasma power and a substrate bias rf power of 1500 and 90 W, respectively. From results of X-ray photoelectron spectroscopy, physical ion bombardment is more effective than chemical reaction for removing Sr, while Ti can be removed by the formation of volatile TiClx. Ba was primarily removed by chemically assisted physical etching (such as that using BaClx) Some etching residues consisting of Ba and Sr were found after the BST films were etched and increased leakage current density. Oxygen surface plasma treatment can effectively repair surface damage caused by etching, and it reduced the leakage current density of the BST capacitor from 4.0 x 10(-7) to 3.0 x 10(-8) A/cm(2) at 1 MV/cm and increased the breakdown field to similar to 2 MV/cm at 1.0 x 10(-6) A/cm(2).