Chemical Vapor Deposition of Zr x Ti 1-x O and Hf x Ti 1-x O Thin Films Using the Composite Anhydrous Nitrate Precursors
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0917-E05-13
Chemical Vapor Deposition of ZrxTi1-xO and HfxTi1-xO Thin Films Using the Composite Anhydrous Nitrate Precursors Qi-Yue Shao1, Ai-Dong Li1, Wen-Qi Zhang1, Di Wu1, Zhi-Guo Liu2, and Nai-Ben Ming2 1 National Laboratory of Solid State Microstructures, Materials Science and Engineering Department, Nanjing University, Nanjing, Jiangsu, 210093, China, People's Republic of 2 National Laboratory of Solid State Microstructures, Physics Department, Nanjing University, Nanjing, Jiangsu, 210093, China, People's Republic of
ABSTRACT Zr/Ti and Hf/Ti composite nitrates were successfully developed as single-source precursors for the chemical vapor deposition of ZrxTi1-xO2 and HfxTi1-xO2 thin films. The Zr/Ti nitrate can be taken as a solid solution of the individual Zr and Ti nitrates, and the Zr/Ti molar ratio in as-deposited ZrxTi1-xO2 films is nicely consistent with that of the precursor. The Hf/Ti nitrate appears to be a mixture of the Hf and Ti nitrates and the composition of the as-deposited HfxTi1-xO2 films depends remarkably on the heating time of precursor. Both ZrxTi1-xO2 and HfxTi1-xO2 films exhibit trading-off properties between band gap and dielectric constant, which suggests that ZrxTi1-xO2 and HfxTi1-xO2 can be the promising candidates for gate dielectric application to improve the scalability and reduce the leakage current of the next generation complementary metal-oxide-semiconductor transistor (CMOS) devices. INTRODUCTION ZrO2, HfO2, their respective silicates and aluminates have been intensively studied as potential high-k materials to replace conventional SiO2 gate dielectric [1-3]. Although Zr (Hf)-silicates (aluminates) exhibit better thermal stability compared to pure ZrO2 (HfO2), they have a low k value due to the incorporation of low dielectric constant SiO2 (Al2O3). Because of high dielectric constant of TiO2, many works on Ti-added composite metal oxides, such as Al-Ti [4], Zr-Ti [5] and Hf-Ti [6] oxides have been attempted to increase the k value and simultaneously maintain favorable properties of Al2O3, ZrO2 and HfO2, such as thermal stability, low leakage current and good interface with Si. Chemical vapor deposition (CVD) is one of the most promising approaches to deposit high-k dielectric films due to its excellent compatibility with Si technology. Metal alkoxides, β-diketonates, and chlorides are the most common precursors for the CVD of metal oxide films. These precursors contain C, H or Cl elements, which can ultimately be incorporated into the films as unwanted impurities. Additionally, the deposition of metal oxide films using these precursors usually needs the introduction of oxidative gases such as O2, O3, H2O or N2O. The presence of these oxidative gases in the reactor can lead to unwanted oxidation of Si substrate and form low dielectric constant SiO2 layers at the interface. Recently, some anhydrous metal nitrates with sufficient volatility have been developed for the CVD of metal oxide thin films,
such as TiO2 [7], ZrO2 [8] and HfO2 [9]. The metal nitrates are carbon- and hy
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