Oblique angled plasma etching for 3D silicon structures with wiggling geometries.

Three dimensional (3D) silicon micro- and nanostructures have attracted special research interest, particularly in photonic and electrochemical devices, due to the extra degrees of freedom for manipulation of device performance and properties. However, it is still considered to be difficult to fabricate 3D silicon structures with an arbitrary geometric form in a scalable volume, especially with standard fabrication techniques, which are intrinsically directional and anisotropic. In this work we proposed a unique method of oblique-angled plasma etching from various angles, thus multilayered silicon structures with wiggling geometries can be fabricated in a controllable manner both in micro- and nanoscale. The mechanism is explained as induced modifications of substrate topology and surface charging when a glass pad is attached on the sample surface, thus the incoming ion fluxes can be directed to the substrate surface with an off-normal angle. The process is convenient to perform without additional modifications on the plasma etching systems. At the same time, it provides more possibilities in the toolkit for fabricating 3D silicon structures with conventional fabrication technologies.