Downscaling of complementary metal-oxide semiconductor (CMOS) gate stacks requires the introduction of ultra-thin and high-k dielectrics such as HfO₂. Atomic layer deposition (ALD) is an excellent technique for producing high-quality high-k films. During ALD, chemical reactions on the substrate surface involve multiple processes that affect the chemical and electrical properties of the deposited films. Thus, the choice of an appropriate precursor for ALD is critical for obtaining high-quality high-k films, leading to good device performance. The aim of this study is to understand the surface reactions during the film growth along with the evaluation of the electrical properties of HfO₂ deposited using two different Hf precursors, HfCl₄ and Hf(N(CH₃)₂)₄. The growth behavior and electrical performance of ALD HfO₂ thin films obtained using the two Hf precursors and H₂O as an oxidant at 250 °C are studied comparatively and discussed as a function of the process parameters, together with surface-reaction energetics determined by the density functional theory. Compared to Hf(N(CH₃)₂)₄, the HfCl₄ shows unfavorable nucleation behavior on the starting Si–OH surfaces. In addition, a more stoichiometric HfO₂ film results from HfCl₄ owing to its high reactivity, leading to lower leakage currents of Si-based devices than that of the film obtained from Hf(N(CH₃)₂)₄. Further, HfCl₄ showed better nucleation on a 2D graphene substrate, leading to superior electrical performance in graphene-based field effect transistors. These results provide practical insights on selecting a suitable Hf precursor for producing gate dielectric layers for future nanoelectronics.

中文翻译：

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由金属卤化物和酰胺前体获得 的原子层沉积HfO ₂薄膜的生长特性和电性能的比较研究†

互补金属氧化物半导体（CMOS）栅堆叠的缩小规模要求引入超薄和高k电介质，例如HfO ₂。原子层沉积（ALD）是生产高质量高k膜的出色技术。在ALD期间，基板表面上的化学反应涉及多个过程，这些过程影响沉积膜的化学和电学性质。因此，选择合适的ALD前驱物对于获得高质量的高k膜至关重要，从而导致良好的器件性能。这项研究的目的是了解薄膜生长过程中的表面反应以及HfO ₂的电性能评估使用两种不同的Hf前体HfCl ₄和Hf（N（CH ₃）₂）_4进行沉积。使用两种Hf前体和H ₂ O作为氧化剂在250°C下获得的ALD HfO ₂薄膜的生长行为和电性能进行了比较研究，并作为工艺参数的函数进行了讨论，还讨论了通过密度泛函理论 与Hf（N（CH ₃）₂）_4相比，HfCl ₄在起始Si-OH表面显示出不利的成核行为。此外，HfCl ₄产生了化学计量更高的HfO ₂膜由于其高反应性，导致硅基器件的漏电流比从Hf（N（CH ₃）₂）₄获得的膜的漏电流低。此外，HfCl ₄在2D石墨烯基板上显示出更好的成核作用，从而在基于石墨烯的场效应晶体管中实现了卓越的电气性能。这些结果为选择合适的H前驱体以生产未来的纳米电子学的栅极介电层提供了实用的见识。