Abstract: An improved structure of a dielectric layer between two adjacent copper wiring lines is disclosed. The dielectric layer is composed of silicon oxide and the adjacent copper wiring lines are formed using a dual damascene process. The structure of the dielectric layer according to the present invention comprises at least one trench in the surface of the dielectric layer, an insulating layer in the trench and at least one void in the insulating layer. The void is used to reduce the effective dielectric constant as well as the parasitic capacitance of the dielectric layer.

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.