To conclude this subsection, reducing the SF 6 flow, and thus pressure of the boost step, did not improve the etch for our application. When the SF 6 flow is reduced too far, for example 50 sccm, the fluorocarbon removal is not complete, resulting in a reduction in pore diameter. In applications where there is still issues with mask undercut which cannot be fixed by reducing the initial etch step time, SF 6 flow may be a useful tool for for controlling the diameters of nanopores.