Method and apparatus for electropolishing

Abstract

The present invention generally includes deposition and electropolishing methods and an apparatus comprising an electroplating cell and auxiliary cell. In one embodiment for electropolishing a substrate, a cycle is performed in which the substrate is alternately placed in an anolyte solution to remove material and a catholyte solution to deposit material. As the cycle is repeated successively, an exposed layer disposed on the substrate is planarized. In another embodiment, an auxiliary cell may be used to deposit the ultrathin seed layer prior to electroplating.

1 . A method for electropolishing, comprising: 
 a) cyclically processing a substrate to planarize an exposed conductive layer: 
 i) exposing the conductive layer to a catholyte solution of a first chemistry; and  
 ii) exposing the conductive layer to an anolyte solution of a second chemistry; and  
   b) detecting an endpoint of the plararization process.    
   
   
       2 . The method of  claim 1 , wherein the cyclical process further comprises: 
 exposing the conductive layer in an vertical orientation to the first and second chemistries.    
   
   
       3 . The method of  claim 1 , wherein the cyclical process further comprises: 
 transferring the substrate between separate compartments of an electropolishing cell, wherein each compartments is configured to supply either the first or the second chemistry.    
   
   
       4 . The method of  claim 1 , wherein the cyclical process further comprises: 
 filling a compartment of an electropolishing cell with the catholyte solution of the first chemistry; and    draining the catholyte solution of the first chemistry from the first compartment; and    filling the compartment of the electropolishing cell with the anolyte solution of the second chemistry.    
   
   
       5 . The method of  claim 1 , wherein the catholyte solution of the first chemistry and the anolyte solution of the second chemistry are recirculated.  
   
   
       6 . The method of  claim 1 , wherein exposing the conductive layer to the catholyte solution further comprises: 
 cooling the substrate to a temperature below or about the freezing point of the catholyte of the first chemistry.    
   
   
       7 . The method of  claim 1 , wherein exposing the conductive layer to the anolyte solution further comprises: 
 cooling the substrate to a temperature below or about the freezing point of the anolyte solution of the first chemistry.    
   
   
       8 . A method for electropolishing, comprising: 
 providing a first and a second substrate, wherein each substrate has a layer deposited thereon;    performing a first sequence of: 
 exposing the layer of the first substrate to a catholyte solution of a first chemistry;  
 exposing the layer of the second substrate to an anolyte solution of a second chemistry;  
 providing a current density to both the first catholyte solution and the first anolyte solution;  
   performing a second sequence of: 
 exposing the layer of the first substrate to an anolyte solution of the second chemistry;  
 exposing the layer of the second substrate to a catholyte solution of the first chemistry;  
 providing a second current density to both the second catholyte solution and the second anolyte solution;  
   repeating at least one of the first and second sequences.    
   
   
       9 . The method of  claim 8 , wherein the providing the first and second substrates further comprises: 
 placing the first and second substrates vertically in separate compartments of an electropolishing cell.    
   
   
       10 . The method of  claim 9 , further comprising: 
 providing the catholyte solution of the first chemistry to the first compartment and providing the anolyte solution of the second chemistry to the second compartment during the first sequence;    draining the catholyte solution of the first chemistry from the first compartment and draining the anolyte solution of the second chemistry from the second compartment; and    providing the catholyte solution of the first chemistry to the second compartment and providing the anolyte solution of the second chemistry to the first compartment during the second sequence.    
   
   
       11 . The method of  claim 10 , further comprising: 
 providing the catholyte solution of the first chemistry to the first compartment and providing the anolyte solution of the second chemistry to the second compartment during the first sequence;    removing the first substrate from the first compartment and placing it in the second compartment; and    removing the second substrate from the second compartment and placing it in the first compartment.    
   
   
       12 . The method of  claim 9 , wherein the catholyte solution of the first chemistry and the anolyte solution of the second chemistry are recirculated.  
   
   
       13 . The method of  claim 9 , further comprising: 
 cooling the first substrate to a temperature below or about the freezing point of the catholyte of the first chemistry during the first sequence; and    cooling the second substrate to a temperature below or about the freezing point of the catholyte of the first chemistry during the second sequence.    
   
   
       14 . The method of  claim 13 , further comprising: 
 cooling the second substrate to a temperature below or about the freezing point of the anolyte of the second chemistry during the first sequence; and    cooling the first substrate to a temperature below or about the freezing point of the anolyte of the second chemistry during the second sequence.    
   
   
       15 . A method for electropolishing, comprising: 
 providing a substrate on a substrate chuck within an electropolishing cell, wherein the substrate has a layer deposited thereon;    contacting an electrolyte to the layer on the substrate within the electropolishing cell;    cooling the substrate to a temperature below or about the freezing point of the electrolyte; and    electropolishing the layer on the substrate.    
   
   
       16 . The method of  claim 15 , wherein cooling further comprises: 
 establishing a temperature gradient of about 0.1° C./μm to about 1° C./μm at the interface of the substrate and the electrolyte.    
   
   
       17 . A method of depositing a seed layer, comprising: 
 positioning a surface of a rotating substrate proximate to but not touching an auxiliary cell;    moving the auxiliary cell across the surface of the substrate;    flowing an electrolyte between an inner vessel and an outer vessel of the auxiliary cell and into contact with the surface of the substrate, wherein the outer vessel surrounds the inner vessel; and    applying power to an electrode in fluid contact with the electrolyte.    
   
   
       18 . An apparatus, comprising: 
 a contact ring configured to retain a substrate against a substrate support;    an electroplating cell;    a robotic arm; and    an auxiliary cell coupled to the robotic arm, wherein the auxiliary cell is located between the contact ring and electroplating cell and wherein the auxiliary cell comprises: 
 a chamber connected to the arm, wherein the chamber has an outer vessel surrounding an inner vessel and wherein electrolyte within the inner vessel can overflow into the outer vessel, a diameter of the outer vessel is small relative to the diameter of the substrate;  
 an electrode within the inner vessel;  
 a diffuser within the inner vessel;  
 an inlet manifold coupled to the inner vessel; and  
 an outlet manifold coupled to the outer vessel.  
   
   
   
       19 . The apparatus of  claim 18 , wherein the inlet is coupled to an electrolyte source.  
   
   
       20 . The apparatus of  claim 18 , wherein the outlet is coupled to the electrolyte source.  
   
   
       21 . The apparatus of  claim 18 , wherein the contact ring and substrate support are moveable between a raised position and a lowered position.