Fabrication of sub-micron silicon vias by deep reactive ion etching

Deep reactive ion etching (DRIE) is a major microfabrication process for micro-electro-mechanical system (MEMS) devices. In recent years DRIE is also applied to make through-silicon-vias (TSVs) for 3D packaging. Typical DRIE-formed TSVs are in the range of a few microns to tens of microns. In the present study, silicon vias with diameters in the sub-micron range (0.5 mu m and 0.8 mu m) are attempted. For comparison purposes, larger silicon vias (1 mu m and 3 mu m) are fabricated as well. In this paper, the microfabrication processes are described. The experimental results and comparisons in terms of via uniformity, aspect ratio dependent etching, undercutting, and effects of various mask materials are discussed in detail.