A Longitudinal Layer-Wise Strategy for Fabricating Tapered Micro-Cones by Ion-Beam Etching

The controllable fabrication of tapered three-dimensional (3D) microstructures by ion-beam processing remains challenging, especially when both profile fidelity and geometric controllability are required. Tapered conical microstructures are of interest because they are relevant to a variety of applications, including micro-optical elements, functional textured surfaces, biomimetic interfaces, and field-enhancing emitter-related structures, where taper angle, aspect ratio, and structural uniformity strongly influence the resulting performance. In this work, a longitudinal layer-wise strategy is proposed for tapered micro-cone fabrication by ion-beam etching. The core idea is to discretize a continuous cone profile along the vertical direction into a sequence of annular layers whose dimensions are determined by the local geometry of the target three-dimensional structure. After this geometric discretization step, each individual layer is executed using a conventional multi-pass strategy, thereby combining longitudinal profile construction with stabilized local material removal. A dedicated pattern-design software, EBWriter, was developed to automatically generate annular patterns and process files from user-defined geometric parameters. Experimental validation was carried out on single-crystal silicon substrates using a dual-beam microscope platform operated at 30 kV. The results show that increasing the longitudinal layer number effectively weakens the staircase effect and improves the continuity of the reconstructed cone profile. For positive micro-cones fabricated using annular patterns with a nominal outer processing diameter of 3 μm, the increasing-inner-radius strategy enables preservation of the cone apex and reconstruction of tapered morphologies with improved fidelity. Under the present processing conditions, an empirical correspondence between the target geometric ratio and the recommended layer number was further summarized: layer numbers of approximately 50, 100, and 300 support cone structures with base-diameter-to-height ratios close to 1:2, 1:3, and 1:4, respectively. In addition, a 3 × 3 positive micro-cone array was successfully fabricated, with a total processing time of about 80 s. The measured cone base diameter and height were 0.886 ± 0.005 μm and 2.354 ± 0.023 μm, respectively, with dimensional variations controlled within ±2%. These results demonstrate that the proposed method provides a feasible layer-wise ion-beam fabrication route for tapered microstructures and offers a useful process basis for future studies on micro-optical surfaces, functional textured interfaces, and emitter-related microstructures.