Lateral-dimension-reducing metallic hard mask etch

Abstract

A combination of gases including at least a fluorocarbon gas, oxygen, and an inert sputter gas is employed to etch at least one opening into an organic photoresist. The amount of oxygen is controlled to a level that limits conversion of a metallic nitride material in an underlying hard mask layer to a metal oxide, and causes organic polymers generated from the organic photoresist to cover peripheral regions of each opening formed in the organic photoresist. The hard mask layer is etched with a taper by the oxygen-limited fluorine-based etch chemistry provided by the combination of gases. The taper angle can be controlled such that a shrink ratio of the lateral dimension by the etch can exceed 2.0.

What is claimed is: 
     
         1 . A structure comprising:
 at least one underlying material layer located on a substrate;   a metallic hard mask layer located on a topmost surface of said at least one underlying material layer; and   a photoresist layer located over said metallic hard mask layer and having a pattern comprising at least one opening therein, wherein a top surface of said metallic hard mask layer underneath said at least one opening is tapered, and an angle between said tapered top surface of said metallic hard mask layer relative a horizontal surface is less than 45 degrees.   
     
     
         2 . The structure of  claim 1 , wherein said angle is from 15 degrees to 40 degrees. 
     
     
         3 . The structure of  claim 1 , wherein said metallic hard mask layer comprises a metal nitride, and a metal oxide material comprising a same metallic element as said metal nitride is present at a surface portion of said tapered top surface of said metallic hard mask layer. 
     
     
         4 . The structure of  claim 3 , wherein said metallic hard mask layer comprises TiN, TaN, WN, a combination thereof, or a stack thereof. 
     
     
         5 . The structure of  claim 1 , wherein an organic polymer derived from a material of said photoresist layer is present on sidewall surfaces of said photoresist layer and on said tapered top surface of said metallic hard mask layer. 
     
     
         6 . The structure of  claim 1 , wherein a ratio of a first lateral dimension of an opening in said metallic hard mask layer as measured at a height of a topmost surface of said metallic hard mask layer to a second lateral dimension of said opening in said metallic hard mask layer as measured at a bottom surface of said metallic hard mask layer and directly underneath a location of measurement of said first lateral dimension is greater than 2.0. 
     
     
         7 . The structure of  claim 6 , wherein said ratio is not less than 3.0. 
     
     
         8 . The structure of  claim 6 , wherein said ratio is not greater than 5.0. 
     
     
         9 . The structure of  claim 6 , wherein said first lateral dimension of said opening in said metallic hard mask layer is substantially the same as a width of the at least one opening in said photoresist layer. 
     
     
         10 . The structure of  claim 9 , wherein said first lateral dimension of said opening in said metallic hard mask layer is equal to a minimum printable dimension for any opening for deep ultraviolet lithography tools, and said second lateral dimension of said opening in said metallic hard mask layer is less than ½ of said minimum printable dimension. 
     
     
         11 . The structure of  claim 1 , wherein said at least one underlying material layer comprises a dielectric material layer. 
     
     
         12 . The structure of  claim 11 , wherein said dielectric material layer comprises undoped silicon oxide, doped silicon oxide, silicon nitride, silicon oxynitride, non-porous organosilicate glass (OSG), and porous OSG. 
     
     
         13 . The structure of  claim 11 , said at least one underlying material layer further comprises a dielectric hard mask layer located between said metallic hard mask layer and said dielectric material layer. 
     
     
         14 . The structure of  claim 13 , said at least one underlying material layer further comprises a dielectric cap layer located between said dielectric material layer and said substrate. 
     
     
         15 . The structure of  claim 14 , wherein said dielectric cap layer comprises silicon nitride, silicon oxynitride, a nitrogen-doped organosilicate glass, or a combination thereof. 
     
     
         16 . The structure of  claim 1 , wherein said substrate comprises a substrate layer including at least one embedded structure. 
     
     
         17 . The structure of  claim 16 , wherein said substrate layer comprises a semiconductor material layer, and said at least one embedded structure comprises at least one semiconductor device. 
     
     
         18 . The structure of  claim 16 , wherein said substrate layer comprises a dielectric material layer, and said at least one embedded structure comprises at least one metal interconnect structure.