Influence of the angle between etched (near) Si{111} surfaces and the substrate orientation on the underetch rate during anisotropic wet-chemical etching of silicon

Anisotropic wet-chemical etching of silicon in alkaline solutions is a key technology in the fabrication of sensors and actuators. In earlier work it was found that not only the etchant and temperature determine the exact anisotropy of etched silicon; the angle between the silicon surface and the mask was also shown to play an important role. In this paper this phenomenon was quantified for several etching conditions. Also, the etch rates of Si{ 100} and Si{ 110} were determined under these conditions, together with the activation energies of these orientations. Finally, the anisotropy ratios (etch depth/underetch) of the etched samples were determined.