Crystallinity-Preserving Atomic Layer Etching of Ultrathin In ₂ O ₃ for Stable Oxide Nanoelectronics

Indium oxide (In 2 O 3 ) is a promising channel material for advanced electronics, offering high electron mobility, a wide bandgap, and excellent compatibility with atomic layer deposition (ALD). However, conventional bottom-up ALD processes cannot achieve and sustain ultrathin crystalline layers owing to poor nucleation behavior and insufficient grain connectivity. Herein, we present an atomic layer etching (ALE) approach for In 2 O 3 that combines hydrogen-plasma-assisted surface modification with acetylacetone (Hacac)-assisted ligand removal. Applying an ALD/ALE etch-back process incorporating this ALE method yielded In 2 O 3 films down to 3 nm that preserved the (222) preferred orientation, as confirmed by grazing-incidence wide-angle X-ray scattering, and exhibited a reduction in root-mean-square roughness from 0.27 nm before etching to 0.17 nm after etching. This process simultaneously maintains the crystallographic order and smooth surface morphology in the ultrathin limit, leading to improved device performance. Therefore, the developed process is considered a viable fabrication route for scalable, high-quality crystalline oxide semiconductors for next-generation nanoelectronics.