Optimization of etching processes for the fabrication of smooth silicon carbide membranes for applications in quantum technology

Recently, it has been demonstrated that Silicon Carbide (SiC) membranes can be used in quantum sensing and MEMS applications. One of the important steps for the production of such membranes is the removal of the substrate material in order to form membranes of micron or submicron thicknesses confining the active regions of fabricated devices to the high quality, doped controlled, epitaxial layers . Moreover, optical components such as Fabry-Pérot cavities and photonic crystals require membranes with smooth surfaces with roughnesses down to the nanometer scale. We report on the development of doping-selective electrochemical processes for the etching of SiC and investigate the creation of such membranes, including the path towards thinner and smoother layers for improved performance. We demonstrate that the resulting roughness of membranes is substantially reduced by novel lithographic patterning and ion beam etching (IBE) procedures to RMS values down to 6 nm.