| Summary: | 碩士 === 國立雲林科技大學 === 電子與資訊工程研究所碩士班 === 89 === The effect of oxygen plasma treatment on the properties of as-deposited 1000Å thick high-dielectric thin films has been investigated. Tantalum pentoxide and Titanium dioxide composite film (Ta2O5)0.92-(TiO2)0.08 was deposited on Pt/Ta/SiO2/Si substrate by RF sputtering method. There is no any intentional heating of the substrate took place during all kinds of deposition conditions. In this article, not only O2 plasma but the furnace annealing , two-step annealing and alternative sputter way were considered.
As deposited (Ta2O5)0.92-(TiO2)0.08 films were exposed under oxygen plasma with different duration . Compared to pure Ta2O5 (ε=25) thin film, significant enhancement in dielectric constant(ε=52) is obtained by 15 minutes of oxygen plasma duration. It was also found that the leakage current density, 3.2 ×10-9 A/cm2 at an applied voltage of 1.5 V, of the (Ta2O5)0.92-(TiO2)0.08 capacitor can be improved by one order of magnitude as compared to that of non-plasma-treated samples. The same result was also found in the alternative sputtering samples. The improvement was suggested to be due to the elimination of oxygen vacancies by oxygen plasma surface treatment or multistage deposition method. Furthermore, the dielectric properties of (Ta2O5)0.92-(TiO2)0.08 films were found to be remarkably sensitive to the post-annealing duration. The dominant conduction mechanism changed from Schottky Emission at low electric field to Poole-Frenkel at high electric field.
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