Abstract: A method for forming an aperture with a uniform void-free sidewall etch profile through a multi-layer insulator layer. There is formed upon a semiconductor substrate a multi-layer insulator layer which has a minimum of a first insulator layer and a second insulator layer. The second insulator layer is formed upon the first insulator layer. There is then etched through a first etch method a first aperture completely through the second insulator layer. The first etch method has: (1) a first perpendicular etch selectivity ratio for the second insulator layer with respect to the first insulator layer of at least about 4:1; and (2) a lateral:perpendicular etch selectivity ratio for the second insulator layer of from about 0.5:1 to about 1:1. The first aperture is then etched through a second etch method to form a second aperture completely through the second insulator layer and the first insulator layer.