Browsing by Author "Lee, Jain-Tsai"

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Improving electrical properties and thermal stability of (Ba,Sr)TiO3 thin films on Cu(Mg) bottom electrodes
(2006-06-01)
Tsai, Kou-Chiang
;
Wu, Wen-Fa
;
Chao, Chuen-Guang
;
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.
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).