Method of forming an interconnect structure

Abstract

A method of forming damascene interconnect structure in an organo-silicate glass layer without causing damage to the organo-silicate glass material. The method includes forming a stack of hardmask layers over the organo-silicate glass layer, defining openings in the hardmask and organo-silicate glass layers using a combination of plasma etch and plasma photoresist removal processes and performing one or more additional plasma etch processes that do not include oxygen containing species to etch the openings to depths required for forming the damascene interconnect structures and to remove any organo-silicate material damaged by the combination of plasma etch and plasma photoresist removal processes.

1 . A method, comprising:
 forming an organo-silicate glass layer over a substrate;   forming a first hardmask layer over said organo-silicate glass layer;   forming a second hardmask layer over said first hardmask layer;   forming a photoresist layer over said second hardmask layer;   removing a region of said photoresist layer;   removing a region of said second hardmask layer where said second hardmask layer is not protected by said photoresist layer using a first plasma etch process;   removing said photoresist layer;   using a second plasma etch process, removing said first hardmask layer where said first hardmask layer is not protected by said second hardmask layer; and   using a third plasma etch process, removing said organo-silicate glass layer in where said organo-silicate glass layer is not protected by said first hardmask layer form a trench extending completely through said organo-silicate glass layer.   
   
   
       2 . The method of  claim 1 , wherein said first and third plasma etch processes include no oxygen or nitrogen containing species. 
   
   
       3 . The method of  claim 1 , further including:
 after said forming said trench, filling said trench with an electrically conductive material; and   performing a chemical mechanical polish to remove said first hardmask layer and co-planarize a top surface of said first hardmask layer and a top surface of said electrically conductive material.   
   
   
       4 . The method of  claim 1 , wherein said organo-silicate glass layer includes about 10% to about 70% voids by volume. 
   
   
       5 . The method of  claim 1 , wherein said organo-silicate glass layer comprises about 10% to about 40% silicon, about 0% to about 30% carbon, about 0% to about 30% nitrogen, and about 20% to about 50% hydrogen. 
   
   
       6 . The method of  claim 1 , further including:
 forming a capping layer between said organo-silicate glass layer and said substrate; and   after said performing said third plasma etch, removing said capping layer in regions of said capping layer not protected by said organo-silicate glass layer using a fourth plasma etch process, wherein said fourth plasma etch process includes no oxygen or nitrogen containing species.   
   
   
       7 . The method of  claim 1 , further including:
 forming an adhesion layer between said organo-silicate glass layer and said first hardmask layer; and   removing a region of said adhesion layer not protected by said second hardmask layer while performing said second plasma etch.   
   
   
       8 . The method of  claim 1 , further including:
 forming a rework protection layer between said first hardmask layer and said second hardmask layer; and   removing a region of said rework protection layer not protected by said first hardmask layer while performing said second plasma etch.   
   
   
       9 . The method of  claim 1 , further including:
 forming an anti-reflective coating between said second hardmask layer and said photoresist layer;   removing a region of said anti-reflective coating not protected by said photoresist layer while performing said first plasma etch; and   removing all remaining anti-reflective coating during said removing said photoresist layer.   
   
   
       10 . The method of  claim 1 , wherein said organo-silicate glass layer is formed by plasma enhanced chemical vapor deposition. 
   
   
       11 . The method of  claim 10 , wherein said organo-silicate glass layer has the structure: 
     
       
         
         
             
             
         
       
     
   
   
       12 . The method of  claim 10 , wherein said organo-silicate glass layer has the structure: 
     
       
         
         
             
             
         
       
     
   
   
       13 . The method of  claim 1 , wherein said organo-silicate glass layer is formed by spin application. 
   
   
       14 . The method of  claim 13 , wherein said wherein said organo-silicate glass layer is a silsequioxane based polymer. 
   
   
       15 . The method of  claim 13 , wherein said wherein said organo-silicate glass layer is formed by spin application of a mixture of silsequioxane based polymer and a porogen followed by removal of said porogen to form voids in said organo-silicate glass layer. 
   
   
       16 . The method of  claim 13 , wherein said organo-silicate glass layer is formed from a resin represented by structures (I), (II), (III) or (IV) 
     
       
         
         
             
             
         
       
       wherein R′ is selected from the group consisting of an alkyl group having 1 to 3 carbon atoms, an aryl group having 6 to 12 carbon atoms, and a cycloalkyl group having 6 to 12 carbon atoms, and wherein R″ is selected from the group consisting of an alkylene group having 1 to 2 carbon atoms and a cycloalkylene group having 6 to 12 carbon atoms. 
     
   
   
       17 . The method of  claim 1 , wherein said first plasma etch is performed using a chlorine containing gaseous compound, chlorine (Cl 2 ), boron tri-chloride (BCl 3 ), a fluorine containing gaseous compound, mono-fluoro methane (CH 3 F), di-fluoro methane (CH 2 F 2 ), tri fluoro methane (CHF 3 ) or combinations thereof mixed with oxygen (O 2 ), nitrogen (N 2 ), hydrogen (H 2 ) or combinations thereof. 
   
   
       18 . The method of  claim 1 , wherein said second plasma etch is performed using a fluorine containing gaseous compound, CH 3 F, CH 2 F 2 , CHF 3 , C X F Y  (where X and Y are positive integers) or combinations thereof mixed with N 2 , H 2 , Ar, Ne, Kr, Xe or combinations thereof. 
   
   
       19 . The method of  claim 1 , wherein said third plasma etch is performed using a fluorine containing gaseous compound, CH 3 F, CH 2 F 2 , CHF 3 , C X F Y  (where X and Y are positive integers) or combinations thereof mixed with N 2 , H 2 , Ar, Ne, Kr, Xe or combinations thereof. 
   
   
       20 . The method of  claim 1 , wherein said second plasma etch, after etching through said second hardmask layer converts a uppermost layer of said organo-silicate glass layer not protected by said second hardmask layer to a carbon depleted organo-silicate glass layer.