Incorporating High-Purity Copper Deposit As Smoothing Step After Direct On-Barrier Plating To Improve Quality Of Deposited Nucleation Metal In Microscale Features

Abstract

Techniques disclosed herein a method and system for coating the interior surfaces of microscale hole features fabricated into the substantially planar surface of a substrate. Techniques include creating a separation or smoothing layer between a nucleation layer process and a metallization or gapfill process. The addition of such a separation layer avoids dissolving a seed layer and gapfill complications from remnant organic material. Techniques include adding a conformal copper smoothing layer step after applying a direct on-barrier nucleation layer. The smoothing layer adds a sufficient thickness so that the gapfill chemistry does not erode the nucleation layer. The smoothing layer can also provide a high-purity copper film that will not detrimentally interact with the TSV gapfill chemistry. This smoothing layer can also provide a surface with consistent roughness to allow uniform adhesion of the organic additives in the TSV gapfill chemistry to create a filling profile that is void-free.

1 . A method for coating surfaces of microscale features fabricated into a substantially planar upper surface of a substrate, the method comprising:
 providing a substrate having a barrier layer that conforms to both an upper planar surface of said substrate and conforms to surfaces of microscale features fabricated into said upper planar surface of said substrate, wherein said barrier layer comprises a metal-containing film that inhibits metal diffusion into said substrate;   plating a nucleation layer directly onto said barrier layer on said surfaces of said microscale features by exposing said substrate to a first liquid-phase plating chemistry containing a metal for metal plating, and causing said first liquid-phase plating chemistry to fully contact said surfaces of said microscale features, said first liquid-phase plating chemistry causing deposition and adhesion of the metal directly onto said barrier layer within said microscale features, the deposition and adhesion yielding a first film thickness of deposited metal on said barrier layer within said microscale features; and   plating a smoothing layer onto said nucleation layer on said surfaces of said microscale features by exposing said substrate to a second liquid-phase plating chemistry containing a second metal for metal plating, and causing said second liquid-phase plating chemistry to fully contact said nucleation layer, said second liquid-phase plating chemistry causing deposition of metal onto said nucleation layer, the deposition and adhesion yielding a second film thickness of deposited metal on said barrier layer within said microscale features such that said smoothing layer defines an opening in said microscale features.   
     
     
         2 . The method of  claim 1 , further comprising:
 providing an electrical contact path at said upper planar surface of said substrate that extends from a perimeter of said substrate to a center of said substrate, said electrical contact path permits generating an electrical potential at an entry to said microscale features.   
     
     
         3 . The method of  claim 2 , wherein said plating a nucleation layer directly onto said barrier layer on said surfaces of said microscale features comprises:
 immersing said substrate in a first chemical bath containing said first liquid-phase plating chemistry that includes metal ions suitable for electrodeposition, causing said first liquid-phase plating chemistry in said first chemical bath to fully contact said surfaces of said microscale features, and applying a first electric potential at said perimeter of said substrate that causes electrodeposition of metal ions onto said barrier layer within said microscale features.   
     
     
         4 . The method of  claim 3 , wherein said plating a smoothing layer onto said nucleation layer comprises:
 immersing said substrate in a second chemical bath containing said second liquid-phase plating chemistry that includes metal ions suitable for electrodeposition, causing said second liquid-phase plating chemistry in said second chemical bath to fully contact said nucleation layer, and applying a second electric potential at said perimeter of said substrate that causes electrodeposition of metal ions onto said nucleation layer within said microscale features, wherein said second electric potential is less than said first electric potential.   
     
     
         5 . The method of  claim 4 , further comprising:
 plating a metal layer onto said smoothing layer applied to said surfaces of said microscale features by immersing said substrate in a third chemical bath containing a third liquid-phase chemistry that includes metal ions suitable for electrodeposition, causing said third liquid-phase plating chemistry in said third chemical bath to fully contact said smoothing layer, and applying a third electric potential at said perimeter of said substrate that causes electrodeposition of metal ions onto said smoothing layer and that fills said microscale features, wherein said third electric potential is less than said first electric potential.   
     
     
         6 . The method of  claim 2 , wherein said providing an electrical contact path comprises: depositing an electrically conductive coating on said upper planar surface of said substrate via vapor deposition, said electrically conductive coating being a metal layer adhered to said barrier layer on said upper planar surface and providing electrical conduction to said microscale features located throughout and across said substrate. 
     
     
         7 . The method of  claim 6 , wherein said electrically conductive coating is a copper layer deposited using physical vapor deposition (PVD) to a thickness of between about 2000 and 5000 angstroms. 
     
     
         8 . The method of  claim 7 , wherein said physical vapor deposition (PVD) excludes ionized PVD, and wherein said electrically conductive coating applied by said physical vapor deposition is at most sparsely applied and discontinuous on said surfaces within said microscale features. 
     
     
         9 . The method of  claim 8 , wherein an aspect ratio of said microscale features is equal to or greater than 10-to-1. 
     
     
         10 . The method of  claim 1 , wherein said first liquid-phase plating chemistry includes a metal ion source for providing metal ions, and a complexing agent that bonds with and causes adhesion of said metal ions directly onto said barrier layer on said surfaces of said microscale features. 
     
     
         11 . The method of  claim 10 , wherein said complexing agent includes a citrate, a tartrate, a sulfate, an acetate, or a fluoroborate, or any combination of two or more thereof. 
     
     
         12 . The method of  claim 1 , wherein said second liquid-phase plating chemistry includes a metal ion source, that provides metal ions, and an acid. 
     
     
         13 . The method of  claim 12 , wherein said second liquid-phase plating chemistry excludes a complexing agent. 
     
     
         14 . The method of  claim 1 , further comprising:
 plating a metal layer onto said smoothing layer applied to said surfaces of said microscale features by exposing said substrate to a third liquid-phase plating chemistry containing metal suitable for metal plating, and causing said third liquid-phase plating chemistry to fully contact said smoothing layer, said third liquid-phase plating chemistry depositing metal onto said smoothing layer and filling said microscale features.   
     
     
         15 . The method of  claim 14 , wherein said third liquid-phase plating chemistry includes a metal ion source, that provides metal ions, and an acid. 
     
     
         16 . The method of  claim 15 , wherein said third liquid-phase plating chemistry excludes a complexing agent. 
     
     
         17 . The method of  claim 15 , wherein said third liquid-phase plating chemistry further includes one or more plating additives selected from the group consisting of a plating leveler, a plating accelerator, and a plating suppressor. 
     
     
         18 . The method of  claim 14 , wherein an acid is added to both said second liquid-phase plating chemistry and said third liquid-phase plating chemistry, and wherein an acid concentration of said acid in said third liquid-phase plating chemistry is greater than an acid concentration of said acid in said second liquid-phase plating chemistry. 
     
     
         19 . The method of  claim 1 , wherein a resistance of the barrier layer is more than about 30 ohm/sq for said substrate. 
     
     
         20 . The method of  claim 1 , wherein said barrier layer includes one or more sub-layers containing one or more metals selected from the group consisting of Ti, Ta, W, Re, Ru, Rh, and Ni. 
     
     
         21 . The method of  claim 1 , wherein said first film thickness exceeds 20 Angstroms, and said second film thickness is less than 1 micron. 
     
     
         22 . The method of  claim 1 , wherein said first film thickness exceeds 100 Angstroms, and said second film thickness is less than 600 nm. 
     
     
         23 . The method of  claim 1 , wherein said first film thickness exceeds 100 Angstroms, and said second film thickness is less than 20 nm. 
     
     
         24 . The method of  claim 1 , wherein said first film thickness ranges from 100 Angstroms to 100 nm. 
     
     
         25 . The method of  claim 1 , wherein said first film thickness ranges from 100 Angstroms to 20 nm. 
     
     
         26 . The method of  claim 1 , wherein said microscale features comprise at least one through-silicon via (TSV). 
     
     
         27 . A substrate processing system for manufacturing microscale structures in a substrate, comprising:
 a first electrochemical cell containing a first chemical bath having metal ions suitable for electrodeposition, said first electrochemical cell being configured to immerse a substrate, having microscale features formed in an upper planar surface thereof and having a barrier layer conformally deposited thereon, in said first chemical bath, said first electrochemical cell configured to cause said first chemical bath to fully contact surfaces of said microscale features, said first electrochemical cell configured to apply a first electric potential at a perimeter of said substrate such that electrodeposition of metal ions onto said surfaces of said microscale features occurs and yields a nucleation layer when said substrate is immersed in said first chemical bath and when said first electric potential is applied;   a first chemical supply system coupled to said first electrochemical cell and configured to supply said first chemical bath with a metal-containing compound, for supplying first metal ions, and a first complexing agent;   a second electrochemical cell containing a second chemical bath having metal ions suitable for electrodeposition, said second electrochemical cell being configured to immerse said substrate, having said microscale features, in said second chemical bath, said second electrochemical cell configured to cause said second chemical bath to fully contact surfaces of said microscale features, said second electrochemical cell configured to apply a second electric potential at said perimeter of said substrate such that electrodeposition of metal ions onto said nucleation layer within said microscale features occurs and yields a smoothing layer when said substrate is immersed in said second chemical bath and when said second electric potential is applied;   a second chemical supply system coupled to said second electrochemical cell and configured to supply said second chemical bath with a second metal-containing compound, for supplying second metal ions, and an acid; and   a controller coupled to said first chemical supply system and said second chemical supply system, and configured to controllably supply said first chemical bath and said second chemical bath with chemical constituents to form a nucleation layer directly on said barrier layer within said microscale features in said first chemical bath and said smoothing layer on said nucleation layer within said microscale features in said second chemical bath without filling said microscale features.   
     
     
         28 . The substrate processing system of  claim 27 , further comprising:
 a third electrochemical cell containing a third chemical bath having metal ions suitable for electrodeposition, said third electrochemical cell being configured to immerse said substrate, having said microscale features, in said third chemical bath, said third electrochemical cell configured to cause said third chemical bath to fully contact surfaces of said microscale features, said third electrochemical cell configured to apply a third electric potential at said perimeter of said substrate such that electrodeposition of metal ions onto said smoothing layer of said surfaces of said microscale features occurs and yields a metal layer that fills said microscale features when said substrate is immersed in said third chemical bath and when said third electric potential is applied; and   a third chemical supply system coupled to said third electrochemical cell, and configured to supply said third chemical bath with a third metal-containing compound for supplying third metal ions, wherein said controller is further coupled to said third chemical supply system, and configured to controllably supply said third chemical bath with chemical constituents for filling said microscale features with metal.