This study investigates molybdenum deposited by atomic layer deposition (ALD) as a potential gate metallization for flash memory devices. Polycrystalline (110)-oriented, with low-resistivity (∼16 μΩ cm) ALD Mo films were deposited on SiO₂ and Al₂O₃ using hydrogen reduction of Mo-oxychloride precursor. On SiO₂, an effective work function (EWF) of 4.75 ± 0.1 eV was obtained for as-deposited samples, and its value increased up to 4.9 ± 0.05 eV upon annealing at 600 °C, whereas on Al₂O₃, a stable EWF value of 5.05 ± 0.05 eV was observed. The EWF variation is correlated with changes in the composition and chemical bonding at the metal/dielectric interface. The latter were investigated by energy dispersive x-ray spectroscopy and electron energy loss spectroscopy performed using scanning transmission electron microscopy and x-ray photoelectron spectroscopy. This analysis revealed that the presence of Mo oxide at the Al₂O₃/Mo interface stabilizes the EWF, and the EWF increase on SiO₂ is attributed to Si enrichment at the SiO₂/Mo interface upon annealing. A theoretical model is suggested to explain the chemical bonding difference on SiO₂ and Al₂O₃, based on the Mo-precursor reactions with the surface groups of the dielectric. This study emphasizes the importance of the precursor/substrate reactions in determining the compositional and, therefore, electrical properties of the metal/dielectric interface, and demonstrates that ALD Mo deposited directly on SiO₂ and Al₂O₃ is a promising candidate for gate metallization of flash devices due to its high EWF.

中文翻译：

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ALD Mo对SiO2和Al2O3的化学键合差异对两种栅叠层有效功函数的影响

本研究调查了通过原子层沉积 (ALD) 沉积的钼作为闪存器件的潜在栅极金属化。使用Mo-氧氯化物前体的氢还原，在SiO ₂和Al ₂ O ₃上沉积具有低电阻率（～16 μ Ω cm）的多晶（110）取向的 ALD Mo膜。在 SiO _{2 上}，沉积样品的有效功函数 (EWF) 为 4.75 ± 0.1 eV，在 600 °C 下退火后其值增加至 4.9 ± 0.05 eV，而在 Al ₂ O _{3 上}，观察到稳定的 EWF 值为 5.05 ± 0.05 eV。EWF 变化与金属/电介质界面处的成分和化学键合的变化相关。后者通过使用扫描透射电子显微镜和 X 射线光电子能谱进行的能量色散 X 射线光谱和电子能量损失光谱进行了研究。该分析表明，Al ₂ O ₃ /Mo 界面上存在的 Mo 氧化物稳定了 EWF，而 SiO ₂上的 EWF 增加归因于退火时SiO ₂ /Mo 界面处的 Si 富集。提出了一个理论模型来解释 SiO ₂和 Al ₂ O ₃上的化学键差异，基于 Mo 前体与电介质表面基团的反应。该研究强调了前驱体/基材反应在决定金属/介电界面的成分和电学性质方面的重要性，并证明直接沉积在 SiO ₂和 Al ₂ O ₃上的 ALD Mo是栅极金属化的有希望的候选者闪存设备由于其高 EWF。