Investigation of the Expansion of an Oxygen Microwave Remote Plasma for the Growth of Functional Oxide Thin Films

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• 作者：G. Al Makdessi ; M. Tabbal
• 关键词：Langmuir probe ; Plasma expansion ; Remote plasma oxidation ; Titanium oxide ; Manganese oxide
• 刊名：Plasma Chemistry and Plasma Processing
• 出版年：2017
• 出版时间：January 2017
• 年：2017
• 卷：37
• 期：1
• 页码：243-255
• 全文大小：
• 刊物类别：Physics and Astronomy
• 刊物主题：Inorganic Chemistry; Classical Mechanics; Characterization and Evaluation of Materials; Mechanical Engineering;
• 出版者：Springer US
• ISSN：1572-8986
• 卷排序：37

文摘

The expansion of an oxygen low-pressure microwave plasma was investigated in order to determine the optimal plasma parameters for the growth of functional oxide semiconductors. Langmuir probe measurements show that the electron density (n_e) increases with the injected power up to a saturation value of 3.0 × 109 cm−3 determined at 10 mTorr while electron temperature (T_e) remains constant at a value of 1.5 eV. When pressure is varied, n_e shows a maximum value at a range from 12 to 20 mTorr while T_e decreases monotonously with increasing pressure. In addition, both n_e and T_e decrease with the axial distance from the plasma source. These effects were discussed through the loss mechanisms in the remote plasma. For a pressure of 13 mTorr and at a substrate temperature of 500 °C, plasma enhanced oxidation of pure metallic Ti thin films lead to the formation of a pure TiO₂ anatase phase compared to a mixed phase of TiO₂ and TiO in the absence of plasma activation. For Mn thin films, the exposure to oxygen remote plasma led to the formation of MnO₂ as opposed to obtaining Mn₃O₄ when oxidation is performed in the oxygen gas ambient. Remote plasma processing was thus found to provide selective pathways to control oxidation states, stoichiometry and phase composition of technologically attractive oxide thin films.