Effect of gate metal on chemical bonding state in metal/Pr-oxide/Ge gate stack structure

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• 作者：Kimihiko Kato ; ¹ ; ^{kkato@alice.xtal.nagoya-u.ac.jp} ; Mitsuo Sakashita ; Wakana Takeuchi ; Noriyuki Taoka ; Osamu Nakatsuka ; Shigeaki Zaima
• 关键词：Germanium ; Praseodymium oxide ; Valence state ; Gate metal ; Reductive reaction
• 刊名：Solid-State Electronics
• 出版年：2013
• 出版时间：May, 2013
• 年：2013
• 卷：83
• 期：Complete
• 页码：56-60
• 全文大小：456 K

文摘

We have investigated the impacts of the gate metal on the chemical bonding state in the metal/Pr-oxide/Ge gate stack structure by the hard X-ray photoelectron spectroscopy method and have tried to explain about the obtained results focusing on the difference of oxygen chemical potential (¦Ì_O) among metal-oxide, Pr-oxide and Ge-oxide. The reductive character of the metals induces the reductive reaction of the Pr-oxide films. The reductive character changes the Pr valence state not only at the surface but also in the Pr-oxide films. The reductive character increases the ratio of Pr³⁺ to Pr⁴⁺ in the Pr-oxide films, suggesting the formation of the crystalline phase with high permittivity of h-Pr₂O₃. The reductive character of the metals also affects on the Pr-oxide/Ge interfacial structure. Besides it leads to the decrease in the amount of Ge atoms bonding with oxygen. These reductive reactions can be explained by ¦Ì_O of the metals with reductive character lower than those of PrO₂ formation and GeO₂ formation. From the comparison of the results for the Ge and Si systems, it was found that the drawing reaction of oxygen, which means the pullout of oxygen in the Pr-oxide film, is facile for the Ge system, relating to ¦Ì_O of GeO₂ higher than that in SiO₂. These results suggest that the selection of gate metals in the metal/Pr-oxide/Ge gate stack structure taking into account ¦Ì_O is quite important to achieve the thin EOT, resulting in both the formation of the h-Pr₂O₃ crystalline phase of the Pr-oxide and the decrease in the amount of Ge-oxides.