Browsing by Author "Chang, Li-Chun"

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Improvement of electrical properties of Ba(0.7)Sr(0.3)TiO(3) capacitors with an inserted nano-Cr interlayer
(2008-07-01)
Ho, Chia-Cheng
;
Chiou, Bi-Shiou
;
Chang, Li-Chun
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電子工程學系及電子研究所
;
Department of Electronics Engineering and Institute of Electronics
The metal-insulator-metal (MIM) capacitors were prepared with Ba(0.7)Sr(0.3)TiO(3)/Cr/Ba(0.7)Sr(0.3)TiO(3) (BST/Cr/BST) dielectric and Pt electrode. The multilayer BST/Cr/BST was sputtered onto Pt/Ti/SiO(2)/Si substrate. The presence of nano-Cr interlayer affects the electrical properties of the capacitors. The temperature coefficient of capacitance (TCC) of capacitors with 2 nm Cr is about 69% of that of capacitors without Cr. In a previous work, the formation of the TiO(2) secondary phase was found after the BST/Cr/BST dielectrics were annealed at 1023 K in O(2) atmosphere for 1 h. It is suggested that the nano-Cr interlayer as a catalyst leads to the TiO(2) formation during the annealing in O(2) atmosphere. The negative value of TCC of BST can be compensated by the positive TCC of TiO(2), and the temperature stability in the dielectric constant can be realized for capacitors with nano-Cr interlayer. The voltage stability of BST is also improved with the insertion of nano-Cr interlayer, and the quadratic coefficient in voltage coefficient of capacitance (VCC) of Pt/BST/Cr(2 nm)/BST/Pt is about 30% of that of the BST capacitor without Cr. The effects of Cr thickness on TCC, VCC, dissipation factor, and leakage current density of Pt/BST/Cr/BST/Pt parallel plate capacitors are investigated.
Microstructure evolution and dielectric properties of Ba0.7Sr0.3TiO3 parallel plate capacitor with Cr interlayer
(2007-12-15)
Ho, Chia-Cheng
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Chiou, Bi-Shiou
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Chang, Li-Chun
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電子工程學系及電子研究所
;
Innovative Packaging Research Center
The microstructure, crystalline phase, surface morphology, and dielectric properties of a sandwich structure of Ba0.7Sr0.3TiO3/Cr/ Ba0.7Sr0.3TiO3 (BST/Cr/BST) dielectric are characterized to understand the influence of the nano-Cr interlayer. BST dielectrics inserted with Cr film of thickness ranged from 2 nm to 15 nm all show the crystalline cubic phase. However, TiO2 layer is formed on the upper BST layer after the BST/Cr/BST dielectrics are annealed at 900 degrees C in O-2 atmosphere for one hour. In this study, TEM, AFM, SEM, X-ray diffraction, and AES are employed to investigate the microstructure evolution of the BST/Cr/BST dielectrics after annealing. The correlations between the microstructure and the dielectric properties of the Pt/BST/Cr/BST/Pt capacitors with various Cr thicknesses are explored. (C) 2007 Elsevier B.V. All tights reserved.
Study on the voltage-controlled-oscillator circuit implemented with Al/HfO2/Si capacitors
(2007)
Pan, Tsai-Sheng
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Chang, Li-Chun
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Ho, Chia-Cheng
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Chiou, Bi-Shiou
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電子工程學系及電子研究所
Voltage controlled oscillator (VCO) is the most ubiquitous element in all communication systems, wired or wireless. In a wireless system the quality of the communication link is determined in large part by the characteristics of the VCO. The capacitance of metal/insulator/semiconductor (MIS) shows larger variation from the accumulation region to the depletion region. The dielectric constant of hafnium dioxide is larger (around 25) than that Of SiO2 (similar to 3.9). Al/Hafnium oxide (HfO2)/Si show a field dependent permittivity and can be used as a dielectric in voltage tunable capacitors. In this work, we used two types of tunable capacitor in the VCO(LC tank and Colpitts circuit) integrated within PCB: one is Al/HfO2/Si (HfO) capacitor, the other one is Philips BB 135 p-n junction capacitor for a control. The maximum MIS capacitance ratio is 4.25. The Al/HfO2/Si capacitors are then implemented as the varactor in the VCO circuit.
Thermal stability and electric properties of Ba0.7Sr0.3TiO3 parallel plate capacitor with nano-Cr interlayer
(2006-12-20)
Ho, Chia-Cheng
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Chiou, Bi-Shiou
;
Chang, Li-Chun
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Chou, Chen-Chia
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Liou, Bo-Heng
A novel sandwich structure of Ba0.7Sr0.3TiO3/Cr/Ba0.7Sr0.3TiO3 (BST/Cr/BST) was sputtered onto Pt/Ti/SiO2/Si substrate. With the insertion of a Cr layer, the leakage currents are decreased and the thermal stability of the specimens is enhanced. Temperature coefficient of capacitance (TCC) of specimens with BST(200 nm)/Cr(2 nm)/BST(200 nm) multifilms can achieve about 83% lower than those with BST (400 nm) monolayer. However, the dielectric constant of the BST(200 nm)/Cr(2 nm)/BST(200 nm) multifilms decreases to about 37% of that BST monolayer. The leakage current densities under an electric field of 125 kV/cm at 90 degrees C are 4 x 10(-4) A/cm(2) and 9 x 10(-1) A/cm(2) for BST(200 nm)/Cr(2 nm)/BST(200 nm) and monolayer BST (400 nm), respectively. X-ray diffraction results indicate the formation of a CrO3 secondary phase after annealing at 700 degrees C or above in O-2 atmosphere. The root causes for the improvement of leakage currents and thermal stability with the insertion of nano-Cr interlayer are explored. The results show the insertion of Cr-nanolayer improves the electric properties for application in capacitors. (c) 2006 Elsevier B.V All rights reserved.
Thickness effects on the electrical characteristics of Ba0.7Sr0.3TiO3 capacitors with nano-Cr interlayer
(2007-03-26)
Ho, Chia-Cheng
;
Chiou, Bi-Shiou
;
Chang, Li-Chun
;
電子工程學系及電子研究所
;
Innovative Packaging Research Center
A multilayer Ba0.7Sr0.3TiO3/Cr/Ba0.7Sr0.3TiO3 (BST/Cr/BST) structure was sputtered sequentially onto Pt/Ti/SiO2/Si substrate. With the insertion of a 2 nm Cr interlayer, the temperature coefficient of capacitance of the BST/Cr/BST dielectric is about 69% lower than that of BST monolayer dielectric. The dielectric constant and dissipation factor as the function of Cr thickness are studied. X-ray diffraction patterns, the analysis results of energy dispersive spectroscopy, and the survey scan profiles of Auger electron spectroscopy reveal the formation of a TiO2 secondary phase after the multilayer is annealed at 800 degrees C in O-2 atmosphere. The insertion of nano-Cr interlayer improves the electrical properties of BST capacitors. (c) 2007 American Institute of Physics.
Thickness-dependent microstructures and electrical properties of CaCu3Ti4O12 films derived from sol-gel process
(2007-12-03)
Chang, Li-Chun
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Lee, Dai-Ying
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Ho, Chia-Cheng
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Chiou, Bi-Shiou
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電子工程學系及電子研究所
CaCu3Ti4O12 (CCTO) thin films with various thicknesses were prepared by a sol-gel multiple coating processes on Pt/Ti/SiO2/Si substrates. Microstructures and surface morphologies of CCTO thin films were analyzed by grazing incident X-ray diffractometer (GIXRD) and scanning electron microscope (SEM), respectively. The correlation between the thickness and electrical properties of CCTO films was investigated. The dielectric constants of CCTO films decreased with increasing film thickness (coating cycle). Both the dielectric constant of CCTO films and interlayer are calculated. Possible mechanisms are explored to explain the thickness dependence of the dielectric constant of CCTO films. (C) 2007 Elsevier B.V. All rights reserved.