Modeling and in Situ Probing of Surface Reactions in Atomic Layer Deposition.
Modeling and in Situ Probing of Surface Reactions in Atomic Layer Deposition.
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DOI：
10.1021/acsami.7b01618
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发表时间：
2017-04
影响因子：
9.5
通讯作者：
Yuanxia Zheng;Sungwook Hong;G. Psofogiannakis;G. Rayner;S. Datta;A. V. van Duin;R. Engel-Herbert
中科院分区：
文献类型：
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作者：
Yuanxia Zheng;Sungwook Hong;G. Psofogiannakis;G. Rayner;S. Datta;A. V. van Duin;R. Engel-Herbert
原子层沉积（ALD）已经成熟为一种卓越的薄膜沉积技术，它提供了一种高度可扩展和经济的途径，可以将化学上不同的材料与良好的厚度控制集成到亚纳米范围。与其广泛的应用相反，对反应过程的定量和全面的理解似乎是无形的。复杂和多种反应途径是可能的，这是强烈影响的表面化学状态。在这里，我们报告了一个综合的建模和实验方法，利用ReaxFF反应力场模拟和原位实时光谱椭偏仪，以深入了解氢化和氧化Ge（100）表面上的三甲基铝和水的Al 2 O3的ALD过程。我们破译了在两个表面上沉积的初始ALD循环期间的不同特性的起源。虽然模拟预测了氢化Ge（100）的成核延迟，但在氧化Ge（100）表面上发现了自清洁效应，并导致混合的Al 2 O3/GeOx层有效地抑制了氧扩散到Ge中。原位椭圆偏振光谱结合非原位原子力显微镜和X射线光电子能谱证实了这些模拟结果。电阻抗表征证明了混合的Al 2 O3/GeOx层的关键作用，以实现具有低界面陷阱密度的电性能良好的电介质/Ge界面。结合的方法可以概括为理解其他ALD前体和表面化学的沉积和反应动力学，这提供了一条路径，在分子水平上的ALD工艺的理论辅助合理设计。
Atomic layer deposition (ALD) has matured into a preeminent thin film deposition technique by offering a highly scalable and economic route to integrate chemically dissimilar materials with excellent thickness control down to the subnanometer regime. Contrary to its extensive applications, a quantitative and comprehensive understanding of the reaction processes seems intangible. Complex and manifold reaction pathways are possible, which are strongly affected by the surface chemical state. Here, we report a combined modeling and experimental approach utilizing ReaxFF reactive force field simulation and in situ real-time spectroscopic ellipsometry to gain insights into the ALD process of Al2O3 from trimethylaluminum and water on hydrogenated and oxidized Ge(100) surfaces. We deciphered the origin for the different peculiarities during initial ALD cycles for the deposition on both surfaces. While the simulations predicted a nucleation delay for hydrogenated Ge(100), a self-cleaning effect was discovered on oxidized Ge(100) surfaces and resulted in an intermixed Al2O3/GeOx layer that effectively suppressed oxygen diffusion into Ge. In situ spectroscopic ellipsometry in combination with ex situ atomic force microscopy and X-ray photoelectron spectroscopy confirmed these simulation results. Electrical impedance characterizations evidenced the critical role of the intermixed Al2O3/GeOx layer to achieve electrically well-behaved dielectric/Ge interfaces with low interface trap density. The combined approach can be generalized to comprehend the deposition and reaction kinetics of other ALD precursors and surface chemistry, which offers a path toward a theory-aided rational design of ALD processes at a molecular level.