To reduce the mask undercut and size of the scallops the first parameter we varied the initial etch step time t i , which was reduced from t i = 3 s to 2 s. To maintain the depth of the pores and to reduce the positive tapering, the etch step time was ramped from t i = 2 s and ending with final etch step time t f = 3 s. In Figure the effects of changing from a 3 s etch step time (Figure ) to a ramp from 2 to 3 s (Figure ) are shown. The depth of the pore is reduced, from 13.8 µm to 11.3 µm with the 2 to 3 s etch step time ramp since the effective etch time has decreased. If desired, this depth can be compensated by increasing the number of cycles or extending the etch cycle end time. With a mask aperture of 450 nm, the 3 second etch gives a larger pore diameter of 550 nm (Figure ), while the 2 to 3 s etch gives a pore diameter of 440 nm (Figure ). Reducing t i from 3 to 2 s has effectively removed the mask undercut and scallop width, resulting in a pore with the same diameter as the mask. Changing from 3 s to 2 to 3 s etch step time ramp also reduces the length of the second scallop from 170 nm to 130 nm, a significant reduction in scallop length as desired.