All-silicon elements of terahertz photonics obtained by plasma etching

In the presented study, nanostructures on a silicon substrate were experimentally formed using the plasma-chemical etching method in a combined discharge plasma. The main objective was to analyze the relationship between the plasma-chemical etching process parameters and the structure geometry, namely: the deviation angle from the vertical, the height of the elements, and deviations from the nominal dimensions. Particular attention was paid to the influence of the active gas concentration, the power of the inductively coupled plasma source (ICP), and the power of the capacitively coupled source (CCP, bias voltage) on the structure geometry. The resulting nanostructures are considered as potential elements of terahertz photonics of metasurfaces. For example, process settings with an ICP power of 400 W, an active gas volume fraction of 7%, and a bias voltage of 101 V made it possible to obtain structures with a height of 136 nm, deviating from the specified dimensions by only 2% (98% compliance).