Micromachining 3D hemispherical features in silicon via micro-EDM

This paper presents an investigation of micro electrical discharge machining (μEDM) as a viable method for micromachining 3D shapes in silicon. The approach integrates a two-step μEDM process with standard silicon microfabrication techniques to create smooth and axisymmetric 3D hemispherical structures with eccentricity, ε ~ 0.11 and a radius variation <; 2%. Through the selection of ultrahard polycrystalline diamond as the μEDM electrode, the low tool wear allows for high throughput machining of 200 wells in silicon within a short total processing time of 80 min. Feasibility of the approach is demonstrated in the fabrication of millimeter scale hemispherical shell structures using the machined silicon features as a mold.