Dogan Gül, Sanli Umut T, Hahn Kersten, Müller Lutz, Gruhn Herbert, Silber Christian, Schütz Gisela, Grévent Corinne, Keskinbora Kahraman
Robert Bosch GmbH, Automotive Electronics, Postfach 13 42, 72703 Reutlingen, Germany.
Max Planck Institute for Intelligent Systems, Heisenbergstrasse 3, 70569 Stuttgart, Germany.
ACS Appl Mater Interfaces. 2020 Jul 22;12(29):33377-33385. doi: 10.1021/acsami.0c06873. Epub 2020 Jul 7.
In many applications of copper in industry and research, copper migration and degradation of metallic copper to its oxides is a common problem. There are numerous ways to overcome this degradation with varying success. Atomic layer deposition (ALD) based encapsulation and passivation of the metallic copper recently emerged as a serious route to success owing to the conformality and density of the ALD films. So far, the majority of the studies have been focused on corrosion protection of copper in a variety of chemical environments, mostly at ambient temperature. An investigation of the stability of the ALD film stacks and copper's interaction with them at elevated temperatures has been lacking. Here, we study the mitigation of copper oxidation and migration in 50 nm thick AlO/TiO and AlO/SiO bilayer ALD stacks. First, the corrosion dynamics were investigated X-ray diffraction (XRD) at 350 °C under atmospheric conditions, and second, the interaction of copper with the passivation layers have been examined using detailed spectro-microscopic investigations. According to the XRD results, both ALD films exhibited excellent oxidation protection. In contrast, bare Cu immediately started to oxidize at 350 °C and transformed entirely to its known oxide phases in 4 h. Spectro-microscopic studies revealed that there are structural and chemical changes on the top surface and within the film stacks. The TiO layer was crystallized during annealing, while the SiO layer stayed in the amorphous phase, which was analyzed by grazing incidence XRD and transmission electron microscopy. According to scanning electron microscopy and X-ray photoelectron spectroscopy analysis, copper was detected on the surface with a higher amount in AlO/TiO than AlO/SiO, 5.2 at.% and 0.7 at.%, respectively. Based on the surface and cross-sectional analysis, copper migration was observed on both layers, albeit more substantially in AlO/TiO. In the case of AlO/SiO, the bulk of the copper was captured at the interface of the two oxides.
在铜在工业和研究中的许多应用中，铜的迁移以及金属铜向其氧化物的降解是一个常见问题。有多种方法来克服这种降解，效果各不相同。基于原子层沉积（ALD）的金属铜封装和钝化最近成为一种成功的重要途径，这得益于ALD薄膜的保形性和致密性。到目前为止，大多数研究都集中在各种化学环境中铜的腐蚀防护上，主要是在室温下。缺乏对ALD薄膜堆叠在高温下的稳定性以及铜与它们相互作用的研究。在此，我们研究了在50 nm厚的AlO/TiO和AlO/SiO双层ALD堆叠中铜氧化和迁移的缓解情况。首先，在大气条件下于350 °C通过X射线衍射（XRD）研究腐蚀动力学，其次，使用详细的光谱显微镜研究来检查铜与钝化层的相互作用。根据XRD结果，两种ALD薄膜都表现出优异的氧化防护性能。相比之下，裸铜在350 °C时立即开始氧化，并在4小时内完全转变为其已知的氧化物相。光谱显微镜研究表明，薄膜堆叠的顶面和内部存在结构和化学变化。通过掠入射XRD和透射电子显微镜分析发现，TiO层在退火过程中结晶，而SiO层保持非晶相。根据扫描电子显微镜和X射线光电子能谱分析，在AlO/TiO和AlO/SiO表面均检测到铜，AlO/TiO表面铜含量更高，分别为5.2原子％和0.7原子％。基于表面和横截面分析，在两层上均观察到铜迁移，尽管在AlO/TiO中更为明显。在AlO/SiO的情况下，大部分铜被捕获在两种氧化物的界面处。
