Uniformity of HfO2 Thin Films Prepared on Trench Structures via Plasma-Enhanced Atomic Layer Deposition

In this study, we assessed the physical and chemical properties of HfO₂ thin films deposited by plasma-enhanced atomic layer deposition (PEALD). We confirmed the self-limiting nature of the surface reactions involved in the HfO₂ thin film's growth by tracing the changes in the growth rate and refractive index with respect to the different dose times of the Hf precursor and O₂ plasma. The PEALD conditions were optimized with consideration of the lowest surface roughness of the films, which was measured by atomic force microscopy (AFM). High-resolution X-ray photoelectron spectroscopy (XPS) was utilized to characterize the chemical compositions, and the local chemical environments of the HfO₂ thin films were characterized based on their surface roughness and chemical compositions. The surface roughness and chemical bonding states were significantly influenced by the flow rate and plasma power of the O₂ plasma. We also examined the uniformity of the films on an 8″ Si wafer and analyzed the step coverage on a trench structure of 1:13 aspect ratio. In addition, the crystallinity and crystalline phases of the thin films prepared under different annealing conditions and underlying layers were analyzed.

Direct Chemisorption-Assisted Nanotransfer Printing with Wafer-Scale Uniformity and Controllability

Nanotransfer printing techniques have attracted significant attention due to their outstanding simplicity, cost-effectiveness, and high throughput. However, conventional methods via a chemical medium hamper the efficient fabrication with large-area uniformity and rapid development of electronic and photonic devices. Herein, we report a direct chemisorption-assisted nanotransfer printing technique based on the nanoscale lower melting effect, which is an enabling technology for two- or three-dimensional nanostructures with feature sizes ranging from tens of nanometers up to a 6 in. wafer-scale. The method solves the major bottleneck (large-scale uniform metal catalysts with nanopatterns) encountered by metal-assisted chemical etching. It also achieves wafer-scale, uniform, and controllable nanostructures with extremely high aspect ratios. We further demonstrate excellent uniformity and high performance of the resultant devices by fabricating 100 photodetectors on a 6 in. Si wafer. Therefore, our method can create a viable route for next-generation, wafer-scale, uniformly ordered, and controllable nanofabrication, leading to significant advances in various applications, such as energy harvesting, quantum, electronic, and photonic devices.