To begin improving etching for photonic crystals, there must be an initial etch process on which to improve. The starting etch process, of which an example is shown in Figure , was based on the one proposed by Grishina that was optimised to give the greatest aspect ratio. While these etch parameters give an impressive aspect ratio up to A = 40, the profile of the pores exhibits a number of undesirable features. In short, I) mask undercut, II) large scallops, III) abrasion of the centre of the pores and IV) positive tapering.