Fabricating method of dual damascene

A fabricating method of dual damascene, performed on a substrate, wherein the substrate contains a patterned conducting layer and devices, the method at least comprising:

• forming a first dielectric layer on the substrate and the conducting layer;
• forming a hard material layer on the first dielectric layer, wherein the hard material layer comprises a first opening located right over the conducting layer to expose the first dielectric layer;
• forming a second dielectric layer on the hard material layer, wherein the second dielectric layer has a low-permissivity;
• performing an enforcement process on the second dielectric layer to make the second dielectric layer solid;
• forming a hard mask layer on the second dielectric layer, wherein the hard mask layer comprises a second opening located right over the first opening, and wherein the second opening has a profile that gradually widens upward;
• performing an etching process on the second dielectric layer, by using the hard mask layer as an etching mask and the hard material layer as a etching stop, to remove a first portion of the second dielectric layer and expose the hard material layer;
• forming a protection layer on the substrate;
• performing an etching back process on the protection layer to leave at least a second portion of the protection layer located on a sidewall of the second dielectric layer, wherein the etching back process also removes a third portion of the first dielectric layer to form a third opening that exposes the conducting layer;
• forming a barrier layer on the substrate;
• and
• forming a second conducting layer in the third opening.