Method for forming openings in low dielectric constant material layer

A method for forming openings in low-k dielectric material layers, comprising:

• providing a substrate containing a metal wire;
• forming a cap layer, a first dielectric layer, a first stop layer, a second dielectric layer, a second stop layer, a metal hard mask layer, a hard mask layer and an anti-reflection layer sequentially on the substrate, wherein the first and second dielectric layers are low-k dielectric layers;
• forming a patterned first photoresist layer on the anti-reflection layer to define the anti-reflection layer, the hard mask layer and the metal hard mask layer, so that a first opening is formed to expose the first stop layer;
• removing the first photoresist layer along with the anti-reflection layer;
• forming a filling material layer on the hard mask layer to fill the first opening;
• forming a patterned second photoresist layer on the filling material layer to define the filling material layer, the second stop layer, the second dielectric layer and the first stop layer, so that a second opening is formed to expose the first dielectric layer;
• removing the second photoresist layer along with the filling material layer;
• performing an anisotropic etching step to form a damascene opening by using the metal hard mask and the hard mask layers as a mask, wherein the damascene opening expose the cap layer;
• and
• removing the exposed cap layer to expose the underlying metal wire.