Although our goal was to reduce the pore widening, changing to a 3-step process also affects other properties of the nanopores. The 3-step process results in shorter nanopores than the 2-step process. This is because both etches used a 3 s etch step and in the 3-step process, 1 s out of 3 was used for the low pressure boost step. At low pressure the etch speed is reduced due to the lower concentration of reactive species. The 3-step process shows a very straight walled profile whilst the 2-step process has a significant positive tapering, even by the same length as the shorter 3-step etched pores. The size of the initial scallops was also reduced when moving to a 3-step process. The reduction in pressure during the boost step increases directionality of the etch and also reduces the speed of the etch, giving a reduction in the width and length of the first scallops. The second scallop of the 2-step process has a width of 530 nm and a length of 170 nm and the second scallop of the 3-step process has a width of 470 nm and a length of 130 nm. From visible inspection, the scallops of the 3-step process appear more uniform and even, with the scallops of the 2-step process often having wavy or curved bottoms. This arises from the decoupling of the fluorocarbon removal and silicon etch steps; in the 2-step process as soon as the fluorocarbon is removed, the etch begins. If the fluorocarbon is removed unevenly then the etch will be uneven. In a 3-step all fluorocarbon is removed before the etching begins, regardless of how even the removal is, allowing for an even, uniform etch.