Process for reducing dishing and erosion during chemical mechanical planarization

Abstract

This invention is directed to a slurry system and process of metal removal from a substrate. This invention is useful for polishing a microelectronic device. This invention is especially useful for chemical mechanical planarization of a semiconductor wafer for removal of an overburden thereof. The slurry system of the present invention includes a first slurry and a second slurry, wherein the first slurry has a higher abrasive concentration than the second slurry. The process of the present invention includes a first polish with the first slurry to partially remove metal from the substrate, and a second polish with the second slurry to further remove metal from the substrate.

1 . A slurry system for removal of a copper metal overburden from a substrate a microelectronic substrate comprising: 
 (a) a first slurry which comprises abrasive and provides for partial removal of said copper metal from said microelectronic substrate, wherein the first slurry defines a first static etch rate of the copper metal overburden; and    (b) a second slurry which provides for further removal of said copper metal from said microelectronic substrate, wherein said first slurry has higher concentration of said abrasive than said second slurry and wherein the second slurry has less than 70% of the static etch rate of the first slurry.    
   
   
       2 . The slurry system of  claim 1  wherein the second slurry has at least 20% of the static etch resistance of the first slurry.  
   
   
       3 . The slurry system of  claim 1  wherein said second slurry is abrasive free.  
   
   
       4 . The slurry system of  claim 1  wherein said abrasive of said first slurry is selected from alumina, titania, zirconia, gennania, silica, ceria, or mixtures thereof.  
   
   
       5 . The slurry system of  claim 1  wherein said abrasive of said first slurry is precipitated silica.  
   
   
       6 . The slurry system of  claim 1  wherein said abrasive is present in an amount of from 0.1 to 30 percent by weight of said first slurry.  
   
   
       7 . The slurry system of  claim 1  wherein at least one of said first and second slurries further comprise an oxidant.  
   
   
       8 . The slurry system of  claim 1  wherein at least one of said first and second slurries further comprise a material selected from complexing agent, anticorrosion agent, stopping compound, polyvalent cation sequestrant, thickener, or mixtures thereof.  
   
   
       9 . The slurry system of  claim 1  wherein at least one of said first and second slurries further comprises a polyvalent cation sequestrant, a anticorrosion agent, and a thickener.  
   
   
       10 . A method for polishing a microelectronic substrate to remove a metal overburden of the microelectronic substrate comprising the steps of: 
 (a) performing a first polish with a first slurry and polishing pad, wherein said first slurry comprises abrasive; and    (b) terminating the first polishing step of (a) prior to removal of the entire metal overburden leaving residual metal overburden on the substrate; and    (c) performing a second polish with a second slurry and polishing pad wherein said first slurry has higher concentration of said abrasive than said second slurry, and wherein the second polishing step is performed to substantially remove only the residual metal overburden of the substrate, wherein the step of substantially removing only the residual metal overburden of the substrate is defined by leaving a trace amount of the residual metal overburden that is less than 5% of the total metal overburden whereby steps a-c) remove more than 95% of the metal overburden.    
   
   
       11 . The method of  claim 10  wherein said metal overburden is copper.  
   
   
       12 . The method of  claim 10  further comprising the step of washing said substrate after completion of said first polish and prior to initiation of said second polish.  
   
   
       13 . The method of  claim 10  wherein the second slurry has less than 70% of the static etch rate of the first slurry.  
   
   
       14 . The method of  claim 10  wherein the metal overburden is copper and the copper removal rate for removing the residual copper in step c) is less than 50% of the removal rate of the copper using the first slurry in step a).  
   
   
       15 . The method of  claim 10  wherein the second slurry is abrasive free and the copper removal rate for removing the residual copper in step c) is less than 25% of the removal rate of the copper using the first slurry in step a).  
   
   
       16 . The method of  claim 10  wherein at least one of said first and second slurries further comprise an oxidant and the copper removal rate for removing the residual copper in step c) is less than 10% of the removal rate of the copper using the first slurry in step a).  
   
   
       17 . A method for polishing a microelectronic substrate to remove a metal overburden of the microelectronic substrate, said method comprising the steps of: 
 (a) applying to a substrate a first slurry which comprises an abrasive for a first polishing of the metal overburden;    (b) terminating the first polishing step of (a) prior to removal of the entire metal overburden leaving residual metal overburden on the substrate; and    (c) applying to said substrate a second slurry, wherein said first slurry has higher concentration of said abrasive than said second slurry, said second slurry has a lower static etch rate than a static etch rate of the first slurry and wherein the second polishing step is performed to substantially remove only the residual metal overburden of the substrate, wherein the step of substantially removing only the residual metal overburden of the substrate is defined by leaving a trace amount of the residual metal overburden that is less than 5% of the total metal overburden whereby steps a-c) remove more than 95% of the metal overburden.    
   
   
       18 . The method of  claim 17  wherein the second slurry has less than 70% of the static etch rate of the first slurry.  
   
   
       19 . The method of  claim 17  further comprising the step of washing said substrate after completion of said first polish and prior to initiation of said second polish.  
   
   
       20 . The method of  claim 10  wherein the copper removal rate for removing the residual copper in step c) is less than 10% of the removal rate of the copper using the first slurry in step a).