To summarise this subsection, moving from a 2-step to a 3-step process results in a reduction of the pore widening as was aimed for. As a bonus, other unwanted features such as mask undercut, large scallops and positive taper were also reduced. On the downside, the nanopore depth was reduced. While this reduction can be regained by adding more cycles, this does significantly lengthen the etch time and require the number of cycles to again be optimised for this new process. Moreover, the already achieved nanopore depths are sufficient for our subsequent 3D photonic crystal fabrication, see the work of van der Broek et al. D. Tapering