Interconnection structure with sidewall protection layer

Abstract

An interconnection structure comprises a first metal structure, a first dielectric layer, a second dielectric layer, a second metal structure, a first protective layer, and a second protective layer. The first dielectric layer is over the first metal structure. The second dielectric layer is over the first dielectric layer. The second metal structure has an upper portion extending through the second dielectric layer, and a lower portion extending through the first dielectric layer. The upper portion has a width greater than a width of the lower portion. The first protective layer spaces the first dielectric layer apart from the lower portion of the second metal structure. The second protective layer spaces the second dielectric layer apart from the upper portion of the second metal structure, and has a top width greater than a top width of the first protective layer.

What is claimed is: 
     
         1 . An interconnection structure comprising:
 a first metal structure;   a first dielectric layer over the first metal structure;   a second dielectric layer over the first dielectric layer;   a second metal structure having an upper portion extending through the second dielectric layer, and a lower portion extending through the first dielectric layer, the upper portion having a width greater than a width of the lower portion;   a first protective layer spacing the first dielectric layer apart from the lower portion of the second metal structure; and   a second protective layer spacing the second dielectric layer apart from the upper portion of the second metal structure, the second protective layer having a top width greater than a top width of the first protective layer.   
     
     
         2 . The interconnection structure of  claim 1 , wherein the first dielectric layer comprises an anti-reflective coating. 
     
     
         3 . The interconnection structure of  claim 2 , wherein the anti-reflective coating is nitrogen-free. 
     
     
         4 . The interconnection structure of  claim 1 , wherein the first dielectric layer comprises an extreme low-k (ELK) dielectric material or a tetrathoxysilane (TEOS) oxide. 
     
     
         5 . The interconnection structure of  claim 1 , wherein the first protective layer comprises silicon nitride or silicon oxynitride. 
     
     
         6 . The interconnection structure of  claim 1 , wherein the second protective layer comprises silicon nitride or silicon oxynitride. 
     
     
         7 . The interconnection structure of  claim 1 , wherein the first protective layer and the second protective layer are formed of a same material. 
     
     
         8 . The interconnection structure of  claim 1 , further comprising:
 a silicon carbide layer between the first metal structure and the first dielectric layer, the lower portion of the second metal structure extending through the silicon carbide layer.   
     
     
         9 . The interconnection structure of  claim 1 , further comprising:
 a nitrogen-containing layer between the first dielectric layer and the second dielectric layer.   
     
     
         10 . The interconnection structure of  claim 9 , wherein the nitrogen-containing layer comprises silicon nitride, silicon oxynitride, or silicon carbon oxynitride. 
     
     
         11 . The interconnection structure of  claim 1 , wherein an interface between the first protective layer and the second metal structure has a different cross-sectional profile than an interface between the second protective layer and the second metal structure. 
     
     
         12 . An interconnection structure comprising:
 a first metal structure;   a liner layer over the first metal structure;   a first dielectric layer over the liner layer;   an etch stop layer over the first dielectric layer;   a second dielectric layer over the etch stop layer;   a second metal structure having an upper portion extending through the second dielectric layer and the etch stop layer, and a lower portion extending through the first dielectric layer and the liner layer to the first metal structure, the lower portion having a sidewall laterally set back from a sidewall of the upper portion; and   a protective layer laterally between the lower portion of the second metal structure and the first dielectric layer, the protective layer extending upwardly from a top surface of the liner layer to a position lower than a top surface of the etch stop layer.   
     
     
         13 . The interconnection structure of  claim 12 , wherein the protective layer forms an interface with the second metal structure, and the interface has a vertical portion and an angled portion extending at an angle from a top end of the vertical portion. 
     
     
         14 . The interconnection structure of  claim 12 , wherein the protective layer has a width decreasing from a position lower than a bottom surface of the etch stop layer to a position level with the bottom surface of the etch stop layer. 
     
     
         15 . The interconnection structure of  claim 12 , wherein the liner layer comprises silicon carbide. 
     
     
         16 . The interconnection structure of  claim 12 , wherein the protective layer comprises silicon nitride or silicon oxynitride. 
     
     
         17 . An interconnection structure comprising:
 a first metal structure;   a first dielectric layer above the first metal structure;   an etch stop layer above the first dielectric layer;   a second dielectric layer above the etch stop layer;   a second metal structure having an upper portion passing through the second dielectric layer and the etch stop layer, and a lower portion passing through the first dielectric layer;   a first protective layer on a sidewall of the first dielectric layer and having a tapered top end; and   a second protective layer on a sidewall of the second dielectric layer and free of a tapered top end.   
     
     
         18 . The interconnection structure of  claim 17 , wherein the tapered top end of the first protective layer is separated from the etch stop layer. 
     
     
         19 . The interconnection structure of  claim 17 , wherein the second metal structure forms a horizontal interface with a top surface of the first dielectric layer. 
     
     
         20 . The interconnection structure of  claim 17 , wherein the etch stop layer comprises silicon nitride, silicon oxynitride, or silicon carbon oxynitride.