  In this manuscript, we outline a reliable procedure to manufacture photonic
nanostructures from single-crystal diamond (SCD). Photonic nanostructures, in
our case SCD nanopillars on thin (< 1$\mu$m) platforms, are highly relevant for
nanoscale sensing. The presented top-down procedure includes electron beam
lithography (EBL) as well as reactive ion etching (RIE). Our method introduces
a novel type of inter-layer, namely silicon, that significantly enhances the
adhesion of hydrogen silsesquioxane (HSQ) electron beam resist to SCD and
avoids sample charging during EBL. In contrast to previously used adhesion
layers, our silicon layer can be removed using a highly-selective RIE step
which is not damaging HSQ mask structures. We thus refine published
nanofabrication processes to ease a higher process reliability especially in
the light of the advancing commercialization of SCD sensor devices.
