Structures and methods for low-k or ultra low-k interlayer dielectric pattern transfer

Abstract

The present invention relates to improved methods and structures for forming interconnect patterns in low-k or ultra low-k (i.e., having a dielectric constant ranging from about 1.5 to about 3.5) interlevel dielectric (ILD) materials. Specifically, reduced lithographic critical dimensions (CDs) (i.e., in comparison with target CDs) are initially used for forming a patterned resist layer with an increased thickness, which in turn allows use of a simple hard mask stack comprising a lower nitride mask layer and an upper oxide mask layer for subsequent pattern transfer. The hard mask stack is next patterned by a first reactive ion etching (RIE) process using an oxygen-containing chemistry to form hard mask openings with restored CDs that are substantially the same as the target CDs. The ILD materials are then patterned by a second RIE process using a nitrogen-containing chemistry to form the interconnect pattern with the target CDs.

1 . A structure comprising a hard mask stack located over an interlevel dielectric structure, wherein the interlevel dielectric structure comprises one or more interlevel dielectric layers that each has a dielectric constant ranging from about 1.5 to about 3.5, and wherein the hard mask stack comprises a lower nitride mask layer and an upper oxide mask layer. 
     
     
         2 . The structure of  claim 1 , wherein the lower nitride mask layer and the upper oxide mask layer each has a thickness ranging from about 100 Å to about 1000 Å. 
     
     
         3 . The structure of  claim 1 , wherein the lower nitride mask layer and the upper oxide mask layer each has a thickness ranging from about 300 Å to about 700 Å. 
     
     
         4 . The structure of  claim 1 , wherein the hard mask stack comprises one or more hard mask openings therein that extend through the lower nitride mask layer and the upper oxide mask layer, and wherein the hard mask openings have critical dimensions ranging from about 20 nm to about 60 nm. 
     
     
         5 . The structure of  claim 4 , further comprising a patterned resist layer located over the hard mask stack, wherein the patterned resist layer has a thickness ranging from about 500 Å to about 2000 Å, and wherein the patterned resist layer comprises one or more resist openings having critical dimensions that are from about 5 nm to about 30 nm smaller than those of the hard mask openings. 
     
     
         6 . The structure of  claim 4 , wherein the interlevel dielectric structure comprises an interconnect pattern that is aligned with the hard mask openings and thereby also has critical dimensions ranging from about 20 nm to about 60 nm. 
     
     
         7 . The structure of  claim 6 , wherein the interlevel dielectric structure comprises at least a first interlevel dielectric layer located over a second interlevel dielectric layer, wherein the first interlevel dielectric layer has one or more wider line openings that extend therethrough and are aligned to the hard mask openings, wherein the second interlevel dielectric layer has one or more narrower via openings therein. 
     
     
         8 . The structure of  claim 1 , wherein the one or more interlevel dielectric layers in the interlevel dielectric structure each comprises one or more materials selected from the group consisting of inorganic dielectric materials, C-doped oxides, F-doped oxides, fluorinated silica glass (FSG), dielectric polymers, organo-silicate materials, SiCOH-containing dielectric materials, spin-on dielectric materials, porous dielectric materials, non-porous dielectric materials, and mixtures or composites thereof. 
     
     
         9 . The structure of  claim 1 , wherein the interlevel dielectric structure further comprises one or more interlevel capping layers each located over one of the one or more interlevel dielectric layers and each having an etching selectivity of at least 10:1 over the interlevel dielectric layers. 
     
     
         10 . The structure of  claim 9 , wherein said one or more interlevel capping layers each comprises one or more materials selected from the group consisting of organo silsesquioxanes, hydrido silsesquioxanes, hydrido-organo silsesquioxanes, siloxanes, silsesquioxanes, silicon carbides, and mixtures or composites thereof.