Fabrication of 3-D Silicon Microneedles Using a Single-Step DRIE Process

Fabrication of 3-D microstructures is one of the most challenging aspects of silicon micromachining. In this paper, we present a novel microfabrication method using one single-step deep reactive ion etching process with gray-scale e-beam lithography mask that offers deeply etched (>350-μm deep) dual-angle 3-D microneedles with control over the height and shape of the structures. Moreover, we found that the shape of the e-beam lithography patterns can determine the general configuration and features of the final etched microneedles, and that the etching process parameters have the most impact on the microneedles´ shape, such as size and vertical base angle. Large arrays of 20 × 20 microneedles with height uniformity of better than 3% are fabricated.