Method of planarization

Abstract

A planarization method that utilizes a chemical-mechanical polishing operation. In the polishing operation, a first slurry for polishing a metallic layer is first employed to remove a greater portion of the metallic layer. Next, a second slurry for polishing a dielectric layer and having properties very similar to the metal-polishing slurry is added and mixed together with the slurry for polishing a metallic layer so that the polishing rate for the dielectric layer is increased. Consequently, metallic residues remaining on the dielectric layer are removed, and a planar dielectric layer is obtained at the same time.

What is claimed is:  
     
         1 . A planarization method that utilizes a chemical-mechanical polishing operation, the method comprising the steps of: 
 providing a semiconductor substrate that has a first metallic layer formed thereon;    forming a dielectric layer over the first metallic layer;    patterning the dielectric layer to form a via opening that exposes a portion of the first metallic layer;    forming a second metallic layer over the dielectric layer that completely fills the via opening;    performing a chemical-mechanical polishing operation, using a first slurry with an oxidant for polishing the second metallic layer, to remove the second metallic layer above the dielectric layer and form a plug inside the opening; and    adding a second slurry containing organic acid groups for polishing the dielectric material without first removing the first slurry, and then continuing the chemical-mechanical polishing operation until the dielectric layer is planarized and metallic residues of the second metallic layer are completely removed.    
     
     
         2 . The method of  claim 1 , wherein step of forming the second metallic layer includes depositing tungsten.  
     
     
         3 . The method of  claim 1 , wherein a pH value of the first slurry and a pH value of the second slurry are about the same.  
     
     
         4 . The method of  claim 1 , wherein the first slurry and the second slurry contain the same type of polishing agents.  
     
     
         5 . The method of  claim 1 , wherein the first slurry has a pH value of between 2.1-2.5, and includes a polishing agent containing silicon dioxide particles with a size of around 200 nm.  
     
     
         6 . The method of  claim 1 , wherein the second slurry has a pH value of between 2.1-2.5, and includes a polishing agent containing silicon dioxide particles with a size of around 200 nm.  
     
     
         7 . The method of  claim 1 , further comprising planarizing the dielectric layer after forming the dielectric layer.  
     
     
         8 . A planarization method that utilizes a chemical-mechanical polishing operation, the method comprising the steps of: 
 providing a semiconductor substrate that has a first metallic layer formed thereon;    forming a dielectric layer over the first metallic layer;    patterning the dielectric layer to form a via opening that exposes a portion of the first metallic layer;    forming a second metallic layer over the dielectric layer that completely fills the via opening;    performing a chemical-mechanical polishing operation, using a first slurry for polishing the second metallic layer, to remove the second metallic layer above the dielectric layer and form a plug inside the opening, wherein the first slurry comprises an oxidant; and    adding a second slurry containing an organic acid for polishing the dielectric material without first removing the first slurry for polishing the second metallic layer, and then continuing the chemical-mechanical polishing operation until the dielectric layer is planarized and metallic residues of the second metallic layer are completely removed, wherein a pH value of the slurry for polishing the second metallic layer and a pH value of the slurry for polishing the dielectric layer are about the same.    
     
     
         9 . The method of  claim 8 , wherein step of forming the second metallic layer includes depositing tungsten.  
     
     
         10 . The method of  claim 8 , wherein the first slurry and the second slurry contain the same type of polishing agents.  
     
     
         11 . The method of  claim 8 , wherein the first slurry has a pH value of between 2.1 to 2.5, and includes a polishing agent containing silicon dioxide particles with a size of around 200 nm.  
     
     
         12 . The method of  claim 8 , wherein the second slurry has a pH value of between 2.1 to 2.5, and includes a polishing agent containing silicon dioxide particles with a size of around 200 nm.