Patent ID: 8084357

Claim:
A method for manufacturing a dual damascene opening comprising a trench opening and a via opening, the method comprising steps of: providing a substrate comprising at least a conductive layer, a base layer, and a dielectric layer; forming a multi cap layer sequentially consisting of a first cap layer, a second cap layer, and a third cap layer directly formed on the dielectric layer; forming a patterned metal hard mask layer on the multi cap layer; and performing an etching process to etch the multi cap layer and the dielectric layer through the patterned metal hard mask layer and to form the trench opening in the dielectric layer, wherein a bottom of the trench opening is in middle of the dielectric layer, wherein the first cap layer is a hermetical tetra-ethyl-ortho-silicate (TEOS) layer, the second cap layer is a tensile stress TEOS layer, and the third cap layer is a hermetical TEOS layer, and wherein the second cap layer is thicker than the first cap layer and the third cap layer; and a thickness ratio between the first cap layer, the second cap layer, and the third cap layer is in a range of 1:2:1 to 1:10:1.