Method of chemical-mechanical polishing

Abstract

A method of polishing a metal layer comprising the following steps. A structure having an upper patterned dielectric layer with an opening therein is provided. A barrier layer is formed over the patterned upper dielectric layer and lining the opening. A metal layer is formed over the barrier layer, filling the opening. A first polish step employing a first slurry composition is conducted to remove a portion of the overlying metal layer. A second polish step employing the first slurry composition is conducted to: polish the partially removed overlying metal layer; and to expose portions of the barrier layer overlying the patterned upper dielectric layer. A third polish step employing a second slurry composition is conducted to remove the exposed barrier layer portions and exposing underlying portions of the patterned upper dielectric layer. A fourth polish step employing the second slurry composition and BTA is conducted to buff the exposed upper dielectric layer portions.

1 . A method for polishing a semiconductor structure, comprising: 
 providing a semiconductor structure having first, second and third material layers;    conducting a first polishing step to remove a first portion of the first material layer;    conducting a second polishing step to remove a second portion of the first material layer and to expose a surface of the second material layer;    conducting a third polishing step to remove at least a portion of the second material layer and to expose a surface of the third material layer;    conducting a fourth polishing step to buff the exposed surface of the third material layer;    wherein the first polishing step comprises using a first slurry, and the third polishing step comprises using a second slurry, and wherein the first and second slurries have different compositions.    
   
   
       2 . The method of  claim 1 , wherein the second polishing step comprises using the first slurry and the fourth polishing step comprises using the second slurry.  
   
   
       3 . The method of  claim 1 , wherein the first slurry has a pH of from about 2.8 to about 4.3 and a particle size of from about 115 nm to about 155 nm; and the second slurry has a pH of from about 9.8 to about 11.4 and a particle size of from about 125 to about 185 nm.  
   
   
       4 . The method of  claim 1 , wherein the second slurry comprises a corrosion inhibitor.  
   
   
       5 . The method of  claim 1 , wherein the first material layer comprises a dielectric material, the second layer comprises a barrier material and the third material layer comprises a conductive material.  
   
   
       6 . The method of  claim 4 , wherein the conductive material comprises copper, aluminum or gold.  
   
   
       7 . The method of  claim 4 , wherein the barrier material comprises Tantalum or Tantalum Nitride.  
   
   
       8 . A method for polishing a multi-layered structure, comprising: 
 providing a semiconductor structure having a plurality of material layers;    conducting a first polishing step using a first slurry to remove a first portion of the plurality of material layers;    conducting a second polishing step using the first slurry to remove a second portion of the plurality of material layers;    conducting a third polishing step using a second slurry to remove a third portion of the plurality of material layers;    conducting a fourth polishing step using the second slurry to remove a fourth portion of the plurality of material layers;    wherein the first and second slurries have substantially different compositions.    
   
   
       9 . The method of  claim 8 , wherein the first slurry is acidic.  
   
   
       10 . The method of  claim 9 , wherein the first slurry has a pH of from about 2.8 to about 4.3.  
   
   
       11 . The method of  claim 8 , wherein the second slurry is alkaline.  
   
   
       12 . The method of  claim 11 , wherein the second slurry has a pH of from about 9.8 to about 11.4.  
   
   
       13 . The method of  claim 8 , wherein the first slurry comprises particles having a size of from about 115 nm to about 155 nm; and the second slurry comprises particles having a size of from about 125 to about 185 nm.  
   
   
       14 . The method of  claim 8 , wherein the first polishing step is performed at a first polishing pressure for a first time period and a second polishing pressure for a second time period, wherein the first polishing pressure is greater than the second polishing pressure.  
   
   
       15 . The method of  claim 14 , wherein the first polishing pressure is from about 2.0 to about 2.4 psi, and the second polishing pressure is from about 1.0 psi to about 1.4 psi.  
   
   
       16 . The method of  claim 8 , wherein the second slurry further comprises a corrosion inhibitor.  
   
   
       17 . A method for performing chemical-mechanical polishing (CMP), comprising: 
 providing a semiconductor structure having a dielectric layer, a barrier layer overlying at least a portion of the dielectric layer, and a metal layer overlying at least a portion of the barrier layer;    conducting a first CMP step using an acidic slurry to remove a first thickness of the semiconductor structure;    conducting a second CMP step the acidic slurry to remove a second thickness of the semiconductor structure;    conducting a third CMP step using an alkaline slurry to remove a third thickness of the semiconductor structure;    conducting a fourth CMP step using the alkaline slurry to remove a fourth thickness of the semiconductor structure;    wherein the first CMP step comprises removing at least a portion of the metal layer and the fourth CMP step comprises buffing a surface of the dielectric layer.    
   
   
       18 . The method of  claim 17 , wherein the acidic slurry has a pH of from about 2.8 to about 4.3.  
   
   
       19 . The method of  claim 17 , wherein the alkaline slurry has a pH of from about 9.8 to about 11.4.  
   
   
       20 . The method of  claim 17 , wherein the first slurry comprises particles having a size of from about 115 nm to about 155 nm; and the second slurry comprises particles having a size of from about 125 to about 185 nm.  
   
   
       21 . The method of  claim 17 , wherein the first CMP step is carried out at a first polishing pressure for a first time period and a second polishing pressure for a second time period, wherein the first polishing pressure is greater than the second polishing pressure.  
   
   
       22 . The method of  claim 17 , wherein the first polishing pressure is from about 2.0 psi to about 2.4 psi, and the second polishing pressure is from about 1.0 to about 1.4 psi.  
   
   
       23 . The method of  claim 17 , wherein the alkaline slurry further comprises a corrosion inhibitor.