Processes and systems for engineering a barrier surface for copper deposition

Abstract

A method for processing an interconnect structure on a substrate is provided, including: depositing a metallic barrier layer to line the interconnect structure, the metallic barrier layer configured to prevent diffusion of copper into the dielectric layer; depositing a thin copper seed layer over the metallic barrier layer in the interconnect structure; depositing a gap-fill copper layer over the thin copper seed layer; removing copper overburden and metallic barrier overburden, wherein removing copper overburden and metallic barrier overburden creates a planarized copper surface on the gap-fill copper layer; selectively depositing a thin layer of a cobalt-containing material on the reduced planarized copper surface; wherein the substrate is processed and transferred in controlled environments to minimize exposure to oxygen, the controlled environments defined by one or more controlled ambient environments and/or one or more vacuum environments.

What is claimed is: 
     
         1 . A method for processing an interconnect structure on a substrate, comprising:
 depositing a metallic barrier layer to line the interconnect structure, wherein the metallic barrier layer is deposited on an exposed surface of an underlying metal and on sidewalls of the interconnect structure defined from a dielectric layer and an etch stop layer, the metallic barrier layer configured to prevent diffusion of copper into the dielectric layer, wherein the metallic barrier layer includes Ta, TaN, Ru, or a combination thereof;   depositing a thin copper seed layer over the metallic barrier layer in the interconnect structure;   depositing a gap-fill copper layer over the thin copper seed layer;   removing copper overburden and metallic barrier overburden, wherein removing copper overburden and metallic barrier overburden creates a planarized copper surface on the gap-fill copper layer;   selectively depositing a thin layer of a cobalt-containing material on the reduced planarized copper surface, the thin layer of cobalt-containing material being configured to inhibit electromigration of the gap-fill copper layer;   wherein the substrate is processed and transferred in controlled environments to minimize exposure to oxygen, the controlled environments defined by one or more controlled ambient environments and/or one or more vacuum environments.   
     
     
         2 . The method of  claim 1 , further comprising:
 reducing a surface of the metallic barrier layer to convert metallic barrier oxide on the surface of the metallic barrier layer to make the surface of the metallic barrier layer to be metal-rich, the metal-rich surface providing a catalytic surface for the deposition of the thin copper seed layer, wherein reducing the surface of the metallic barrier layer is performed by a hydrogen-containing plasma.   
     
     
         3 . The method of  claim 1 , further comprising:
 cleaning the exposed surface of the underlying metal, wherein cleaning the exposed surface of the underlying metal removes surface metal oxide;   wherein cleaning the exposed surface of the surface metal oxide is accomplished by using one of an Ar sputtering process or a plasma process using a fluorine-containing gas, wherein the fluorine-containing gas is NF 3 , CF 4 , or a combination of both.   
     
     
         4 . The method of  claim 1 , wherein depositing the metallic barrier layer includes depositing a first metallic barrier layer having a thickness between about 10 angstroms to about 150 angstroms, and depositing a second metallic barrier layer having a thickness between about 10 angstroms to about 50 angstroms. 
     
     
         5 . The method of  claim 4 ,
 wherein the first metallic barrier layer is a thin tantalum nitride (TaN) layer providing conformal coverage over the interconnect structure; and   wherein the second metallic barrier layer is a thin tantalum (Ta) layer promoting adhesion to the copper seed layer.   
     
     
         6 . The method of  claim 5 ,
 wherein depositing the first metallic barrier layer is performed by an atomic layer deposition (ALD) process; and   wherein depositing the second metallic barrier layer is performed by a physical vapor deposition (PVD) process or an ALD process.   
     
     
         7 . The method of  claim 1 , further comprising:
 after removing the copper overburden and metallic barrier overburden, and before selectively depositing the thin layer of cobalt-containing material, removing metal-organic complex contaminants and metal oxides from the substrate surface, removing organic contaminants from the substrate surface, and reducing the planarized copper surface that is removed of metal-organic complex contaminants, metal oxides, and organic contaminants.   
     
     
         8 . The method of  claim 7 , wherein the metal-organic complex contaminants include copper-benzotrizole (Cu-BTA) complex. 
     
     
         9 . The method of  claim 8 , wherein removing metal-organic complex contaminants is performed by using a wet clean with a cleaning solution containing tetramethylammonium hydroxide (TMAH) or complexing amines 
     
     
         10 . The method of  claim 7 , wherein removing metal oxides is performed by using a wet clean with a cleaning solution containing citric acid. 
     
     
         11 . The method of  claim 7 , wherein removing organic contaminants is performed by an oxygen plasma process with process temperature less than about 120° C. to prevent forming a thick copper oxide layer on the copper surface. 
     
     
         12 . The method of  claim 1 , wherein the cobalt-containing material is selected from the group consisting of CoWP, CoWB, and CoWBP. 
     
     
         13 . The method of  claim 1 , wherein removing the copper overburden and metallic barrier overburden is performed by a chemical mechanical polishing (CMP) process that exposes a top surface of the dielectric layer in which the interconnect structure was etched. 
     
     
         14 . The method of  claim 1 ,
 wherein depositing the metallic barrier layer is performed by a physical vapor deposition process; and   wherein depositing the gap-fill copper layer is performed by an electrochemical plating (ECP) process.   
     
     
         15 . A method for processing an interconnect structure on a substrate, comprising:
 cleaning an exposed surface of an underlying metal at a bottom of the interconnect structure, wherein cleaning the exposed surface of the underlying metal removes surface metal oxide, wherein cleaning the exposed surface of the surface metal oxide is accomplished by using one of an Ar sputtering process or a plasma process using a fluorine-containing gas, wherein the fluorine-containing gas is NF 3 , CF 4 , or a combination of both;   depositing a metallic barrier layer to line the interconnect structure, wherein the metallic barrier layer is deposited on the exposed surface of the underlying metal and on sidewalls of the interconnect structure defined from a dielectric layer and an etch stop layer, the metallic barrier layer configured to prevent diffusion of copper into the dielectric layer, wherein the metallic barrier layer includes Ta, TaN, Ru, or a combination thereof;   reducing a surface of the metallic barrier layer to convert metallic barrier oxide on the surface of the metallic barrier layer to make the surface of the metallic barrier layer to be metal-rich, the metal-rich surface providing a catalytic surface for the deposition of the thin copper seed layer, wherein reducing the surface of the metallic barrier layer is performed by a hydrogen-containing plasma;   depositing a thin copper seed layer over the metallic barrier layer in the interconnect structure;   depositing a gap-fill copper layer over the thin copper seed layer;   removing copper overburden and metallic barrier overburden, wherein removing copper overburden and metallic barrier overburden creates a planarized copper surface on the gap-fill copper layer;   selectively depositing a thin layer of a cobalt-containing material on the reduced planarized copper surface, the thin layer of cobalt-containing material being configured to inhibit electromigration of the gap-fill copper layer;   wherein the substrate is processed and transferred in controlled environments to minimize exposure to oxygen, the controlled environments defined by one or more controlled ambient environments and/or one or more vacuum environments.   
     
     
         16 . The method of  claim 15 , wherein depositing the metallic barrier layer includes depositing a first metallic barrier layer having a thickness between about 10 angstroms to about 150 angstroms, and depositing a second metallic barrier layer having a thickness between about 10 angstroms to about 50 angstroms;
 wherein the first metallic barrier layer is a thin tantalum nitride (TaN) layer providing conformal coverage over the interconnect structure; and   wherein the second metallic barrier layer is a thin tantalum (Ta) layer promoting adhesion to the copper seed layer;   wherein depositing the first metallic barrier layer is performed by an atomic layer deposition (ALD) process; and   wherein depositing the second metallic barrier layer is performed by a physical vapor deposition (PVD) process or an ALD process.   
     
     
         17 . The method of  claim 15 , further comprising:
 after removing the copper overburden and metallic barrier overburden, and before selectively depositing the thin layer of cobalt-containing material, removing metal-organic complex contaminants and metal oxides from the substrate surface, removing organic contaminants from the substrate surface, and reducing the planarized copper surface that is removed of metal-organic complex contaminants, metal oxides, and organic contaminants;   wherein the metal-organic complex contaminants include copper- benzotrizole (Cu-BTA) complex;   wherein removing metal-organic complex contaminants is performed by using a wet clean with a cleaning solution containing tetramethylammonium hydroxide (TMAH) or complexing amines;   wherein removing metal oxides is performed by using a wet clean with a cleaning solution containing citric acid;   wherein removing organic contaminants is performed by an oxygen plasma process with process temperature less than about 120° C. to prevent forming a thick copper oxide layer on the copper surface.   
     
     
         18 . The method of  claim 15 , wherein the cobalt-containing material is selected from the group consisting of CoWP, CoWB, and CoWBP. 
     
     
         19 . The method of  claim 15 , wherein removing the copper overburden and metallic barrier overburden is performed by a chemical mechanical polishing (CMP) process that exposes a top surface of the dielectric layer in which the interconnect structure was etched. 
     
     
         20 . The method of  claim 15 ,
 wherein depositing the metallic barrier layer is performed by a physical vapor deposition process; and   wherein depositing the gap-fill copper layer is performed by an electrochemical plating (ECP) process.