Crystal orientation dependent etching in RIE and its application

We found that an appropriate mixture of SF₆, C₄F₈ and O₂ gases in a standard Inductively Coupled Plasma Reactive Ion Etching (ICP-RIE) apparatus achieves crystal orientation dependent etching. The etched shapes after the RIE of silicon wafers with (100), (110), and (111) surface orientation are investigated by the masks with circular openings and isolated pattern. The results of the etching process show (111) terraces; i.e., the etching rate of the (111) plane is slower than that of other planes similar to the alkaline-based wet etching. The etching rate in the horizontal direction in each crystallographic orientation is examined by etching a wagon wheel pattern. We also demonstrate an application, Through-Silicon Via (TSV) holes with horn-shaped openings using this process.