Electrochemical/ mechanical polishing

Abstract

An electrochemical/mechanical polishing apparatus and method to planarize surfaces of a semiconductor device without damaging relatively soft dielectric materials. The electrochemical/mechanical polishing apparatus comprises a substrate chuck, nozzle assembly, power supply, and sweep mechanism. The substrate chuck receives a substrate to be processed. The nozzle assembly includes a nozzle plate having a plurality of nozzles to dispense an electrolyte solution. A pad is secured to the nozzle plate. The power supply provides a positive electric potential to an electrically conductive layer of the substrate and a negative electric potential to the nozzle plate. The sweep mechanism scans the nozzle assembly along the surface of the substrate, and the pad is positioned sufficiently close to the surface of the substrate to disturb an electrolyte/wafer boundary layer.

What is claimed is:  
     
         1 . An apparatus comprising: 
 a substrate chuck to receive a substrate;    a nozzle assembly comprising: 
 a nozzle plate having a plurality of nozzles to dispense an electrolyte solution; and  
 a pad secured to the nozzle plate;  
   a power supply to provide a positive electric potential to an electrically conductive layer of the substrate and to provide a negative electric potential to the nozzle plate; and    a sweep mechanism to scan the nozzle assembly along the surface of the substrate, the pad positioned sufficiently close to the surface of the substrate to disturb an electrolyte/wafer boundary layer.    
     
     
         2 . The apparatus of  claim 1 , wherein the pad is relatively soft and porous.  
     
     
         3 . The apparatus of  claim 1 , wherein the nozzle assembly further comprises an elongated body having a chamber to receive the electrolyte solution, and wherein the nozzle plate is disposed on the elongated body.  
     
     
         4 . The apparatus of  claim 1 , wherein the nozzle plate comprises stainless steel.  
     
     
         5 . The apparatus of  claim 1 , wherein the nozzle plate is a linear cathode and the substrate is an anode to electrochemically/mechanically remove a portion of the electrically conductive layer from the substrate.  
     
     
         6 . The apparatus of  claim 1 , wherein the substrate is a semiconductor wafer.  
     
     
         7 . The apparatus of  claim 1 , further comprising: 
 a chamber having a top opening, the chamber providing a reservoir for the electrolyte solution, the chamber containing the nozzle assembly and the sweep mechanism;    a lid to cover the top opening of the chamber, the substrate chuck disposed on an interior surface of the lid to downwardly face a frontside of the wafer when the lid is secured to the chamber, and the nozzle assembly located below the substrate to form an interlectrode gap, the electrolyte solution filling the interelectrode gap, the electrochemical/mechanical polishing occurring where the electrolyte solution impinges over the nozzle plate.    
     
     
         8 . The apparatus of  claim 7 , further comprising: 
 a nozzle pump to draw the electrolyte solution from the reservoir and to pump the electrolyte solution to the nozzle assembly.    
     
     
         9 . A method comprising: 
 providing a positive electric potential to an electrically conductive layer of a substrate;    providing a negative electric potential to a linear nozzle plate;    directing a jet of electrolyte solution from the linear nozzle plate to the electrically conductive layer of the substrate;    providing a pad on the linear nozzle plate to disturb an electrolyte/substrate boundary layer; and    scanning the linear nozzle plate along the surface of the electrically conductive layer of the substrate to uniformly electrochemically/mechanically polish the electrically conductive layer.    
     
     
         10 . The method of  claim 9 , maintaining an interelectrode gap during said scanning, the interelectrode gap being the distance between the surface of the substrate and the surface of the linear nozzle plate.  
     
     
         11 . The method of  claim 9 , further comprising: 
 forming the pad from a relatively soft and porous material to saturate the pad with the electrolyte solution.    
     
     
         12 . The method of  claim 9 , further comprising: 
 providing a chamber having a reservoir to contain the electrolyte solution and the linear nozzle plate;    sealing the chamber with a lid, the lid having a substrate chuck to receive the substrate, the conductive layer of the substrate facing downwardly when the chamber is sealed with the lid, the linear nozzle plate disposed below the wafer;    channeling spent electrolyte solution away from the pad;    returning the spent electrolyte solution to the reservoir; and    recirculating the spent electrolyte with the electrolyte solution.    
     
     
         13 . The method of  claim 12 , further comprising: 
 maintaining the electrolyte solution at a target temperature.    
     
     
         14 . The method of  claim 9 , wherein said scanning the linear nozzle plate further comprises sweeping the linear nozzle plate from one end of the substrate to an opposite end of the substrate.  
     
     
         15 . The method of  claim 9  wherein said directing a jet of electrolyte solution from the linear nozzle plate to the electrically conductive layer of the substrate further comprises: 
 coupling the linear nozzle plate with a chamber;  
 pumping the electrolyte solution from the reservoir to the chamber to pressurize the electrolyte solution; and  
 impinging jets of electrolyte solution onto the surface of the wafer.  
 
     
     
         16 . The method of  claim 9 , wherein said providing a pad on the linear nozzle plate planarizes the surface of the wafer by establishing a metal removal rate which is greater at peaks of the surface of the substrate than at valleys of the surface of the substrate.  
     
     
         17 . A method comprising: 
 forming a dielectric layer on a substrate;    patterning and etching the dielectric layer to form trenches;    covering the dielectric layer with an electrically conductive layer;    electrochemically/mechanically polishing the surface of the substrate, said electrochemically/mechanically polishing comprising: 
 directing a jet of electrolyte solution from the linear nozzle plate to the electrically conductive layer of the substrate;  
 providing a pad on the linear nozzle plate to disturb an electrolyte/substrate boundary layer; and  
 scanning the linear nozzle plate along the surface of the electrically conductive layer to uniformly electrochemically/mechanically polish the electrically conductive layer.  
   
     
     
         18 . The method of  claim 17 , further comprising: 
 providing a positive electric potential to the electrically conductive layer; and    providing a negative electric potential to a linear nozzle plate.    
     
     
         19 . The method of  claim 17 , wherein the electrically conductive layer is electrochemically/mechanically polished to form interconnect lines for a semiconductor device, and wherein the substrate is a silicon wafer.  
     
     
         20 . The method of  claim 17 , wherein the surface of the substrate is electrochemically/mechanically polished to the extent that a surface of the conductive layer is coplanar with a surface of the dielectric layer.  
     
     
         21 . The method of  claim 17 , wherein the dielectric layer is an ULK dielectric material.  
     
     
         22 . The method of  claim 17 , wherein the electrically conductive layer is copper.  
     
     
         23 . The method of  claim 17 , further comprising: 
 maintaining an interelectrode gap during said scanning, the interelectrode gap being the distance between the surface of the substrate and a surface of the linear nozzle plate.    
     
     
         24 . An apparatus comprising: 
 a substrate;    a dielectic layer on the substrate, the dielectric layer having trenches;    interconnect lines within the trenches, the interconnect lines having an electrically conductive material, the electrically conductive material and the dielectric layer partially removed by an electrochemical/mechanical polishing apparatus to form an upper surface of the dielectric layer which is coplanar with an upper surface of the electrically conductive material.    
     
     
         25 . The apparatus of  claim 24 , wherein the electrochemical/mechanical polishing apparatus comprises: 
 a linear nozzle plate to dispense an electrolyte solution onto the substrate;    a pad secured to the linear nozzle plate;    a power supply to negatively bias the linear nozzle plate and to positively bias the electrically conductive bias; and    a sweep mechanism to scan the linear nozzle plate along the surface of the substrate, the pad positioned sufficiently close to the surface of the substrate to disturb an electrolyte/wafer boundary layer.    
     
     
         26 . The apparatus of  claim 25 , wherein the substrate is a silicon wafer to form a semiconductor device.  
     
     
         27 . The apparatus of  claim 26 , wherein the semiconductor device is an integrated circuit.  
     
     
         28 . The apparatus of  claim 26 , wherein the dielectric layer is an ULK dielectric material, and wherein the electrically conductive material is copper.