Zhu Lin, Yang Geng-Lai, Ding Wen-Juan, Cao Yan-Qiang, Li Wei-Ming, Li Ai-Dong
National Laboratory of Solid State Microstructures, Materials Science and Engineering Department, College of Engineering and Applied Sciences, Collaborative Innovation Center of Advanced Microstructures, Nanjing University, Nanjing 210093, P. R. China.
Jiangsu Leadmicro Nano-Technology Co., Ltd, Wuxi, Jiangsu, People's Republic of China.
Dalton Trans. 2022 Jun 27;51(25):9664-9672. doi: 10.1039/d2dt01358d.
The conformal coating or surface modification in high aspect ratio nanostructures is a tough challenge using traditional physical/chemical vapor deposition, especially for metal deposition. In this work, the growth behavior of iridium (Ir) metal formed by atomic layer deposition (ALD) in anodic aluminum oxide (AAO) templates was explored deeply. It is found that the surface hydrophilicity is crucial for the nucleation of ALD Ir. An ALD AlO layer with an ultra-hydrophilic surface can greatly promote the nucleation of ALD Ir in AAO nanopores. The effect of the Ir precursor pulse time, diameter, and length of AAO nanopores on the infiltration depth of ALD Ir was investigated systematically. The results show that the infiltration depth of ALD Ir in AAO nanopores is in proportion to the pore diameter and the square root of the Ir precursor pulse time, which follows a diffusion-limited model. Furthermore, the Ir precursor pulse time to obtain conformal Ir coating throughout all the AAO channels is in proportion to the square of the aspect ratio of AAO templates. In addition, the conformal Ir deposition in AAO nanopores is also related to the Ir precursor purge time and the O partial pressure. Insufficient Ir purge time could cause a CVD-like reaction, leading to the reduction of the infiltration depth in AAO. Higher O partial pressure can facilitate Ir nucleation with more Ir precursor consumption at the entrance of nanopores, decreasing the infiltration depth in AAO nanopores, so appropriate O partial pressure should be chosen for ALD Ir in high aspect ratio materials. Above all, our research is valuable for surface modification or coating of metal by ALD in high aspect ratio nanostructures for 3D microelectronics, nano-fabrication, catalysis and energy fields.
在高深宽比纳米结构中进行 conformal 涂层或表面改性，使用传统的物理/化学气相沉积是一项艰巨的挑战，尤其是对于金属沉积而言。在这项工作中，深入探索了通过原子层沉积（ALD）在阳极氧化铝（AAO）模板中形成铱（Ir）金属的生长行为。发现表面亲水性对于ALD Ir的成核至关重要。具有超亲水表面的ALD AlO层可以极大地促进AAO纳米孔中ALD Ir的成核。系统地研究了Ir前驱体脉冲时间、AAO纳米孔的直径和长度对ALD Ir渗透深度的影响。结果表明，ALD Ir在AAO纳米孔中的渗透深度与孔径和Ir前驱体脉冲时间的平方根成正比，这遵循扩散限制模型。此外，在所有AAO通道中获得 conformal Ir涂层的Ir前驱体脉冲时间与AAO模板的纵横比的平方成正比。此外，AAO纳米孔中的 conformal Ir沉积还与Ir前驱体吹扫时间和O分压有关。Ir吹扫时间不足可能会导致类似CVD的反应，导致AAO中渗透深度降低。较高的O分压可以促进Ir成核，在纳米孔入口处消耗更多的Ir前驱体，从而降低AAO纳米孔中的渗透深度，因此对于高深宽比材料中的ALD Ir，应选择合适的O分压。最重要的是，我们的研究对于通过ALD在高深宽比纳米结构中进行金属的表面改性或涂层在3D微电子、纳米制造、催化和能源领域具有重要价值。
