<title>Silicon waveguides fabrication process based on the anisotropic etching of Si<111>-oriented wafers</title>

Abstract

The fabrication process of c-Si waveguides based on the anisotropic etching of Si<111> oriented wafers is described. To obtain c-Si waveguides, the anisotropic etching was combined with an isotropic pre-etch step to a depth equal to the thickness of the final c-Si freestanding structure, followed by side-wall passivation. In addition, a second pre-etching step was performed to establish the depth of the air gap that acts as the bottom cladding of the waveguide. Freestanding c-Si waveguides with very smooth surfaces were obtained by anisotropic etching in a KOH solution. By using a Si₃N₄/SiO₂ mask layer, double waveguides were obtained. The possible applications of c-Si based free standing structures include devices for optical communications and evanescent-wave bio- or chemical sensors.