Oxidation-State-Dependent Selective Atomic Layer Etching of Metal Oxides

Abstract

Atomic layer etching (ALE) that interacts synergistically with area-selective deposition significantly enhances its accuracy, establishing it as a key technique for the precise control of material deposition and removal in the manufacturing of sub-10 nm nanoelectronics. In this study, we report a method for selectively performing ALE on various metal oxides, including ZnO, MgO, Al2O3, Y2O3, SiO2, and ZrO2, using acetylacetone (Hacac) and ozone (O3). This approach exploits the unique chelate coordination properties of β-diketonates, in which two oxygen atoms can simultaneously attach to a single metal center, forming highly volatile chelate complexes. By leveraging these properties, we demonstrate the potential for selective ALE based on the oxidation state of the metal in these compounds, facilitating the formation of volatile metal-ligand complexes and enabling precise, oxidation state-dependent material removal. The selective ALE characteristics are validated through various analytical techniques, including X-ray fluorescence, spectroscopic ellipsometry, scanning electron microscopy, and energy-dispersive X-ray spectroscopy mapping. Additionally, the layer-by-layer etching is elucidated through the use of an in situ quartz crystal microbalance, while an in situ residual gas analyzer tracks the etching dynamics and uncovers the underlying mechanism. This approach offers a method for tailoring etch processes to the unique properties of target materials, providing the precise control and selectivity essential for nanoscale precision. The ability to selectively remove specific materials enables the advancement of innovative designs and complex architectures in cutting-edge nanoelectronics. © 2025 American Chemical Society.