Nb-Taの陽極酸化膜の誘電特性*

概要

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Nb-Ta mixed thin films prepared by DC sputtering were anodized for the purpose of extending the properties of tantalum thin film capacitor. Dielectric properties (capacitance, tan∂and temperature coefficient of capacitance) were investigated as a function of tantalum contents in mixed films. For the determination of thickness of anodic oxide films, sputter ecthing of the anodized films has been carried out varying ecthing times. The thickness obtained by the sputter ecthing method was compared with the values calculated according to Gerstenberg’s equation. It is reasonable to say that the agreements between both values are fairly good, taking into account the measurement errors of interferometric method. Dielectric constants of mixed anodic oxide films calculated by Wagner’s theory were compared with the values obtained from measured values of oxide thickness and capacitance. The agreements are also good. Therefore, we can conclude that mixed anodic oxide films in this work are very uniform and have ideally mixed structure. Furthermore, it is seen that the value of dielectric constant can be changed from 33 to 26 by changing tantalum contents in mixed films, above the region of 50 atm. ％, maintaining constant value of tan ∂below 0.01.
北見工業大学の論文