Control of removal rates in CMP

Abstract

A two-step method for chemical mechanical polishing of a semiconductor substrate having successive layers, comprised of, a metal layer, an underlying barrier film and an underlying dielectric layer. The first polishing step is performed utilizing a slurry composition selective to the metal in the metal layer, to remove the metal at a high removal rate during polishing, and the second polishing step is performed utilizing a slurry composition selective to the barrier film and least selective to the metal layer and the underlying dielectric layer. In an alternate embodiment, the second polishing step is performed with a slurry equally selective to the barrier layer and the underlying dielectric layer and least selective to the metal of the metal layer, to remove the barrier layer at a high removal rate during polishing, and level a surface of the dielectric layer to the surface of the metal interconnection structure in the underlying dielectric layer.

What is claimed is:  
     
         1 . A method for chemical mechanical polishing (CMP) of a semiconductor substrate having a metal layer, an underlying barrier film and an underlying dielectric layer with metal interconnection structures, comprising the steps of: 
 removing the metal layer by first step CMP utilizing a first step slurry that is highly selective to the metal of the metal layer and less selective to the barrier material of the barrier film to remove the metal of the metal layer with a maximized rate of metal removal by polishing, and to minimize removal of the barrier material of the barrier film; and    removing the barrier material by second step CMP utilizing a second step slurry that is highly selective to the barrier material and is least selective to the metal layer and the dielectric layer, to remove the barrier film with a maximized rate by polishing, with minimized removal of the metal of the metal layer and minimized removal of the dielectric layer to provide the height of the dielectric layer at a surface level with the metal interconnection structures; wherein said second step slurry has a pH greater than 7.    
     
     
         2 . The method as recited in  claim 1 , wherein the step of removing the barrier film by second step CMP utilizes a second step slurry having a pH greater than 7, and a dispersion of colloidal silica having a Zeta Potential of negative (20 millivolts or greater) at said pH.  
     
     
         3 . The method as recited in  claim 1 , wherein the step of removing the barrier film by second step CMP utilizes a second step slurry having a pH greater than 7, and submicron abrasive particles of colloidal silica comprising up to about 30% by weight of said second step slurry.  
     
     
         4 . The method as recited in  claim 1 , wherein the step of removing the barrier film by second step CMP utilizes a second step slurry having a pH greater than 7, a dispersion of colloidal silica having a zeta potential of negative (20 millivolts or greater) at said pH, and submicron abrasive particles of colloidal silica comprising up to about 30% by weight of said second step slurry.  
     
     
         5 . The method as recited in  claim 1 , wherein the step of removing the barrier film by second step CMP utilizes a second step slurry; wherein said second step slurry comprises: submicron abrasive partices of colloidal silica comprising up to about 30% by weight of said second step slurry; a complexing agent up to about 5,000 ppm by weight of said second step slurry; a corrosion inhibitor up to about 110 ppm by weight of said second step slurry; a biocide up to about 200 ppm by weight of said second step slurry; an oxidizing agent up to about 15,000 ppm by weight of said second step slurry; an oxide suppressant up to about 5,000 ppm by weight of said second step slurry; and a chloride salt up to about 200 ppm by weight of said second step slurry.  
     
     
         6 . The method as recited in  claim 5 , wherein the step of removing the barrier film by second step CMP utilizes said second step slurry having a Zeta Potential of negative (20 millivolts or greater) at said pH.  
     
     
         7 . The method as recited in  claim 5 , wherein the step of removing the barrier film by second step CMP utilizes a second step slurry having a complexing agent selected from the group consisting of: malic acid, tartaric acid, gluconic acid, glycolic acid, citric acid, phthalic acid, pyrocatechol, pyrogallol, gallic acid, and tannic acid.  
     
     
         8 . The method as recited in  claim 5 , wherein the step of removing the barrier film by second step CMP utilizes a second step slurry having a copper corrosion inhibitor.  
     
     
         9 . The method as recited in  claim 5 , wherein the step of removing the barrier film by second step CMP utilizes a second step slurry having hydrogen peroxide as the oxidizing agent.  
     
     
         10 . The method as recited in  claim 5 , wherein the step of removing the barrier film by second step CMP utilizes a second step slurry having ammonium chloride as the chloride salt.  
     
     
         11 . The method as recited in  claim 5 , wherein the step of removing the barrier film by second step CMP utilizes a second step slurry having polyvinylpyrrolidone as the oxide suppressant.  
     
     
         12 . A method for polishing a semiconductor substrate having a metal layer, an underlying barrier film and an underlying dielectric layer with metal interconnect structures, comprising the steps of: 
 removing the metal layer by first step CMP utilizing a first step slurry that is highly selective to the metal of the metal layer and less selective to the barrier film to remove the metal of the metal layer with a maximized rate of metal removal by polishing, and to minimize removal of the barrier film; and    removing the dielectric layer and barrier film by second step CMP utilizing a second step slurry that is equally highly selective to the barrier material and the dielectric material and least selective to the metal in the metal layer; wherein said second step slurry comprises a pH greater than 7; submicron abrasive partices of colloidal silica comprising up to about 30% by weight of said second step slurry; a complexing agent up to about 5,000 ppm by weight of said second step slurry; a corrosion inhibitor up to about 110 ppm by weight of said second step slurry; a biocide up to about 200 ppm by weight of said second step slurry; and an oxidizing agent up to about 15,000 ppm by weight of said second step slurry.    
     
     
         13 . The method as recited in  claim 12 , wherein the step of removing the barrier film or alternately the dielectric material by second step CMP utilizes said second step slurry having a Zeta potential of negative (20 millivolts or greater) at said pH.  
     
     
         14 . The method as recited in  claim 12 , wherein the step of removing the barrier film or alternately the dielectric material by second step CMP utilizes a second step slurry having a complexing agent selected from the group consisting of: malic acid, tartaric acid, gluconic acid, glycolic acid, citric acid, phthalic acid, pyrocatechol, pyrogallol, gallic acid, and tannic acid.  
     
     
         15 . The method as recited in  claim 12 , wherein the step of removing the barrier film or alternately the dielectric material by second step CMP utilizes a second step slurry having a copper corrosion inhibitor.  
     
     
         16 . The method as recited in  claim 12 , wherein the step of removing the barrier film by second step CMP utilizes a second step slurry having hydrogen peroxide as the oxidizer.  
     
     
         17 . An aqueous polishing composition for polishing semiconductor substrates comprising: a pH greater than 7; submicron abrasive partices of colloidal silica comprising up to about 30% by weight of said second step slurry; a complexing agent up to about 5,000 ppm by weight of said second step slurry; a corrosion inhibitor up to about 110 ppm by weight of said second step slurry; a biocide up to about 200 ppm by weight of said second step slurry; an oxidizing agent up to about 15,000 ppm by weight of said second step slurry; an oxide suppressant up to about 5,000 ppm by weight of said second step slurry; and a chloride salt up to about 200 ppm by weight of said second step slurry.  
     
     
         18 . A polishing composition according to  claim 17  wherein said complexing agent is citric acid.  
     
     
         19 . A polishing composition according to  claim 17  wherein said corrosion inhibitor is selected from a group consisting of benzotriazole, tolyltriazole and mixtures thereof.  
     
     
         20 . A polishing composition according to  claim 17  wherein the oxidizing agent is hydrogen peroxide.  
     
     
         21 . A polishing composition according to  claim 17  wherein the chloride salt is ammonium chloride.  
     
     
         22 . An aqueous polishing composition for polishing semiconductor substrates comprising a pH greater than 7; submicron abrasive partices of colloidal silica comprising up to about 30% by weight of said second step slurry; a complexing agent up to about 5,000 ppm by weight of said second step slurry; a corrosion inhibitor up to about 110 ppm by weight of said second step slurry; a biocide up to about 200 ppm by weight of said second step slurry; and an oxidizing agent up to about 15,000 ppm by weight of said second step slurry.  
     
     
         23 . A polishing composition according to  claim 22  wherein said complexing agent is citric acid.  
     
     
         24 . A polishing composition according to  claim 22  wherein said corrosion inhibitor is selected from a group consisting of benzotriazole, tolyltriazole and mixtures thereof.  
     
     
         25 . A polishing composition according to  claim 22  wherein the oxidizing agent is hydrogen peroxide.