Smoothing of microfabricated silicon features by thermal annealing in reducing or inert atmospheres

Reordering of silicon surface as a result of annealing in reducing or inert environment at high temperature has gained interest recently. Annealing in pure hydrogen and preferably in reduced pressure has been studied for more than a decade to reduce the surface roughness that originates from wet or deep reactive ion etching (DRIE). The study has widened into high-throughput engineering involving now also argon atmosphere. In contrast to hydrogen, the rearrangement of atoms starts abruptly and requires absence of oxygen and nitrogen. The potential applications of silicon surface annealing include mirror surfaces and low-loss waveguides in integrated optics, electrical vias through silicon wafers, and various microsystems, such as membranes, filters, microresonators and microfluidic structures.