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-
$\mu \text{m}$
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
$20\times 20$
microneedles with height uniformity of better than 3% are fabricated. [2014-0209]