Methods and chemistry for providing initial conformal electrochemical deposition of copper in sub-micron features

Abstract

A method for electrolytically repairing a copper seed layer. The method includes positioning the seed layer in fluid communication with a low conductivity seed layer repair solution, wherein the low conductivity seed layer repair solution includes a copper concentration of less than about 20 g/l, a pH of less than about 4, a chlorine ion concentration of between about 20 ppm and about 100 ppm, and an additive organic surfactant configured to suppress a copper deposition rate in the concentration range of 200 ppm to 2000 ppm. The method further includes applying a seed layer repair bias configured to generate a current density of less than about 5 mA/cm 2 across the seed layer and cleaning the repaired seed layer in pure water containing less than 1 ppm chloride ions.

1 . A method for electrolytically repairing a copper seed layer, comprising: 
 positioning the seed layer in fluid communication with a low conductivity seed layer repair solution, the low conductivity seed layer repair solution comprising: 
 a copper concentration of less than about 20 g/l;  
 a pH of less than about 4;  
 a chlorine ion concentration of between about 20 ppm and about 100 ppm; and  
 an additive organic surfactant configured to suppress a copper deposition rate at a concentration of between about 100 ppm and about 2000 ppm; and  
   applying a seed layer repair bias configured to generate a current density of less than about 5 mA/cm 2  across the seed layer.    
     
     
         2 . The method of  claim 1 , wherein the pH of the seed layer repair solution is greater than about 1.5.  
     
     
         3 . The method of  claim 1 , wherein the additive organic surfactant comprises at least one of polyethylene glycol and copolymers of ethylene oxide-propylene oxide.  
     
     
         4 . The method of  claim 1 , wherein an electrical conductivity of the seed layer repair solution is between about 6 mS/cm and about 20 mS/cm.  
     
     
         5 . The method of  claim 1 , wherein positioning the seed layer comprises immersing the seed layer into the seed layer repair solution while simultaneously applying a forward immersion bias to the seed layer.  
     
     
         6 . The method of  claim 1 , wherein the copper concentration is between about 3 g/l and about 10 g/l.  
     
     
         7 . The method of  claim 1 , wherein the low conductivity seed layer repair solution further comprises between about 0.1 g/l and about 1.0 g/l of acid.  
     
     
         8 . A method for filling a semiconductor feature having a seed layer deposited thereon with a conductive material, comprising: 
 positioning the seed layer in a first plating solution, the first plating solution comprising a pH of between about 1.5 and about 4.0 and a copper concentration of between about 3 g/l and about 10 g/l;    applying a first plating bias to the seed layer to plate a metal onto discontinuities in the seed layer, the first plating bias being configured to generate a first current density across the seed layer of less than about 5 mA/cm 2 ;    removing the seed layer from the first plating solution;    cleaning the seed layer of residual chemical constituents from the first plating with a cleaning solution, wherein the cleaning solution comprises less than about 1 ppm of chlorine ions;    positioning the seed layer in a second plating solution, the second plating solution being different from the first plating solution; and    applying a second plating bias to the seed layer to deposit a feature fill layer, wherein the second plating bias is configured to generate a second current density across the seed layer that is greater than the first current density.    
     
     
         9 . The method of  claim 8 , wherein the first plating solution further comprises: 
 a copper concentration of between about 3 g/l and about 20 g/l;    a chlorine concentration of between about 20 ppm and about 100 ppm; and    an organic surfactant at a concentration of between about 100 ppm and 2000 ppm.    
     
     
         10 . The method of  claim 9 , wherein the organic surfactant comprises at least one of polyethylene glycol and copolymers of ethylene oxide-propylene oxide.  
     
     
         11 . The method of  claim 9 , further comprising adding an organic wetting agent based on non-ionic surfactants at a concentration of between about 50 ppm and about 500 ppm.  
     
     
         12 . The method of  claim 9 , further comprising adding an organic anti-foaming agent based on non ionic surfactant at a concentration of between about 50 ppm and about 500 ppm.  
     
     
         13 . The method of  claim 8 , wherein cleaning the seed layer further comprises: 
 transferring the substrate to a spin rinse dry cell;    rotating the substrate at a rate of between about 400 rpm and about 1000 rpm; and    dispensing deionized water onto the seed layer to remove chemical constituents therefrom.    
     
     
         14 . The method of  claim 8 , wherein positioning the seed layer in the first and second plating solutions further comprises applying a cathodic bias to the seed layer during the immersion process, the cathodic bias being configured to overcome seed layer etching caused by the plating solution.  
     
     
         15 . The method of  claim 8 , wherein the second plating solution comprises copper ions at a concentration of between about 30 g/l and about 60 g/l, chlorine ions at a concentration of between about 20 ppm and about 100 ppm, an organic plating suppressor additive at a concentration of between about 100 ppm and about 2000 ppm, a leveler additive at a concentration of between about 1 ml/l to about 10 ml/l, and a plating accelerator additive at a concentration of between about 5 ppm and about 60 ppm.  
     
     
         16 . The method of  claim 8 , wherein the second plating bias is configured to generate a current density of between about 3 mA/cm 2  and about 10 mA/cm 2  across a plating surface of the substrate.  
     
     
         17 . The method of  claim 8 , wherein the first plating solution has a conductivity of between about 5 mS/cm and about 20 mS/cm.  
     
     
         18 . A method for plating a metal onto a discontinuous seed layer, comprising: 
 immersing the seed layer in a low conductivity electrolytic plating solution having a pH of between about 1.5 and about 3.0;    applying an electrical bias to the seed layer that is configured to generate a current density of between about 1 mA/cm 2  and about 5 mA/cm 2  across the seed layer;    removing the seed layer from the low conductivity electrolytic plating solution;    rinsing the seed layer of residual chemicals;    immersing the seed layer in a conductive gap fill electrolytic solution having a pH of less than about 4; and    applying a gap fill bias to the seed layer to electrolytically fill features formed thereon, the gap fill bias being configured to generate a current density of between about 3 mA/cm 2  and about 10 mA/cm 2  across the seed layer.    
     
     
         19 . The method of  claim 18 , wherein immersing the substrate into the low conductivity electrolytic plating solution and the conductive gap fill solution further comprises applying a forward immersion bias to the seed layer during the immersion, the forward immersion bias being configured to overcome etching of the seed layer by the solutions during immersion.  
     
     
         20 . The method of  claim 18 , wherein the low conductivity electrolytic plating solution further comprises a copper concentration of between about 3 g/l and about 10 g/l and an acid concentration of between about 0.1 g/l and about 2.0 g/l.  
     
     
         21 . The method of  claim 20 , wherein the low conductivity electrolytic plating solution further comprises an organic suppressor surfactant at a concentration of between about 200 ppm and about 2000 ppm.  
     
     
         22 . A low conductivity electrolytic seed layer repair solution for semiconductor processing, comprising: 
 copper sulfate at a concentration of between about 3 g/l and 20 g/l;    acid at a concentration of between about 0.1 g/l and 2 g/l;    chlorine ions at a concentration of between about 20 ppm and 70 ppm; and    an additive suppressor surfactant at a concentration of between about 200 ppm and 2000 ppm.