High aspect ratio and steepness TiO2 metasurface fabrication via stepwise mixed-gas ICP etching

The fabrication of high-aspect-ratio nanostructures determines the optical field modulation capability of devices, while high steepness ensures consistency between design and experimental results. However, a rapid and low-cost experimental testing remain challenging. To address this, this paper proposes a novel stepwise inductively coupled plasma (ICP) etching method based on mixed gases, combining the high selectivity of CHF₃-based etching gases with the high anisotropy of BCl₃-based chemical etching. This method enables the fabrication of high-quality TiO_₂ metasurfaces with an aspect ratio exceeding 7, a sidewall tilt angle below 1^°, and a rapid prototyping time of 10 minutes. Compared to direct mixed-gas etching, experiments demonstrate superior control over the steepness of meta-atoms, providing a universal and reliable solution for future high-performance micro/nanodevice fabrication.