Balasubramanyam Shashank, Merkx Marc J M, Verheijen Marcel A, Kessels Wilhelmus M M, Mackus Adriaan J M, Bol Ageeth A
Department of Applied Physics, Eindhoven University of Technology, 5600 MB Eindhoven, The Netherlands.
Eurofins Materials Science Netherlands B.V., High Tech Campus 11, 5656 AE Eindhoven, The Netherlands.
ACS Mater Lett. 2020 May 4;2(5):511-518. doi: 10.1021/acsmaterialslett.0c00093. Epub 2020 Apr 8.
With downscaling of device dimensions, two-dimensional (2D) semiconducting transition metal dichalcogenides (TMDs) such as WS are being considered as promising materials for future applications in nanoelectronics. However, at these nanoscale regimes, incorporating TMD layers in the device architecture with precise control of critical features is challenging using current top-down processing techniques. In this contribution, we pioneer the combination of two key avenues in atomic-scale processing: area-selective atomic layer deposition (AS-ALD) and growth of 2D materials, and demonstrate bottom-up processing of 2D WS nanolayers. Area-selective deposition of WS nanolayers is enabled using an ABC-type plasma-enhanced ALD process involving acetylacetone (Hacac) as inhibitor (A), bis(-butylimido)-bis(dimethylamido)-tungsten as precursor (B), and HS plasma as the co-reactant (C) at a low deposition temperature of 250 °C. The developed AS-ALD process results in the immediate growth of WS on SiO while effectively blocking growth on AlO as confirmed by in situ spectroscopic ellipsometry and ex situ X-ray photoelectron spectroscopy measurements. As a proof of concept, the AS-ALD process is demonstrated on patterned AlO/SiO surfaces. The AS-ALD WS films exhibited sharp Raman ( and ) peaks on SiO, a fingerprint of crystalline WS layers, upon annealing at temperatures within the thermal budget of semiconductor back-end-of-line processing (≤450 °C). Our AS-ALD process also allows selective growth on various TMDs and transition metal oxides while blocking growth on HfO and TiO. It is expected that this work will lay the foundation for area-selective ALD of other 2D materials.
随着器件尺寸的缩小，二维（2D）半导体过渡金属二硫属化物（TMDs）如WS正在被视为未来纳米电子学应用中有前景的材料。然而，在这些纳米尺度下，使用当前的自上而下加工技术在器件架构中精确控制关键特征来整合TMD层具有挑战性。在本论文中，我们率先将原子尺度加工中的两条关键途径相结合：区域选择性原子层沉积（AS-ALD）和二维材料生长，并展示了二维WS纳米层的自下而上加工。使用一种ABC型等离子体增强ALD工艺实现了WS纳米层的区域选择性沉积，该工艺涉及乙酰丙酮（Hacac）作为抑制剂（A）、双（-丁基亚氨基）-双（二甲基氨基）-钨作为前驱体（B）以及HS等离子体作为共反应物（C），沉积温度为250℃。原位椭偏光谱和非原位X射线光电子能谱测量证实，所开发的AS-ALD工艺在SiO上能使WS立即生长，同时有效地阻止在AlO上的生长。作为概念验证，在图案化的AlO/SiO表面展示了AS-ALD工艺。在半导体后端制程热预算（≤450℃）范围内的温度下退火后，AS-ALD的WS薄膜在SiO上呈现出尖锐的拉曼（ 和 ）峰，这是结晶WS层的特征。我们的AS-ALD工艺还允许在各种TMD和过渡金属氧化物上选择性生长，同时阻止在HfO和TiO上的生长。预计这项工作将为其他二维材料的区域选择性ALD奠定基础。
