To reduce the width of the first scallops, and thus the mask undercut, the angular distribution of the reactive species or the number of etching species must be reduced by the following set of parameters. Reducing the pressure increases the mean free path of the ions and thus reduces the angular distribution ∆θ. To reduce the length of the first scallops, the number of etching species in the first etch steps must be reduced. The number of etching species is affected by the etch step time and the pressure. In addition, the capacitively coupled plasma (CCP) power also affects the energy of the ions and their ability for remove fluorocarbon from the bottom of the pores. A high CCP power results in more ions with sufficient energy to reach the bottom of the pore and remove the fluorocarbon to continue the etching process, but a too high CCP power in the early etch steps increases mask undercut and scallop size by contributing to removal of fluorocarbon from the walls by ions with a shallow angle. The effects of these parameters are further explored in the following subsections.