Process for the chemical-mechanical polishing of isolation layers produced using the STI technology, at elevated temperatures

Abstract

A process for the chemical-mechanical polishing of isolation layers based on the shallow trench isolation (STI) technology, using a basic polishing slurry which contains from about 5 to about 12.5% by weight of a colloidal silica abrasive, characterized in that the polishing slurry is applied to the wafer surface at a temperature of about 35° C. to about 80° C., increases the polishing selectivity with regard to the rate at which silica is removed compared to the rate at which silicon nitride is removed.

What is claimed is:  
     
         1 . A chemical-mechanical polishing process comprising applying a basic polishing slurry containing from about 5 to about 12.5% by weight of a colloidal silica abrasive to a wafer surface at a temperature ranging from about 35° C. to about 80° C. and polishing the wafer surface.  
     
     
         2 . The process according to  claim 1 , wherein the polishing slurry is applied at a temperature ranging from about 65° C. to about 75° C.  
     
     
         3 . The process according to  claim 1 , wherein the polishing slurry contains from about 6 to about 10% by weight of a colloidal silica abrasive.  
     
     
         4 . The process according to  claim 1 , wherein the polishing slurry contains from about 8 to about 15% by weight of a metal fluoride.  
     
     
         5 . The process according to  claim 4 , wherein the metal fluoride is selected from the group consisting of lithium fluoride, sodium fluoride and potassium fluoride.  
     
     
         6 . The process according to  claim 5 , wherein the metal fluoride is potassium fluoride.  
     
     
         7 . The process according to  claim 1 , wherein the process polishes a composite material which contains silica and silicon nitride.  
     
     
         8 . The process according to  claim 1 , wherein the pH at 22° C. of the polishing slurry is higher than about 10.5.  
     
     
         9 . The process according to  claim 1 , wherein the colloidal silica has a mean particle size ranging from about 10 nm to about 1 μm.  
     
     
         10 . A process comprising applying, at a temperature ranging from about 35° C. to about 80° C., a basic polishing slurry containing from about 5 to about 12.5% by weight of a colloidal silica abrasive to a surface of a wafer comprising a trench filled with SiO 2  and surface covered with a film of silica and polishing the wafer surface.  
     
     
         11 . The process according to  claim 10 , wherein the polishing slurry is applied at a temperature ranging from about 65° C. to about 75° C.  
     
     
         12 . The process according to  claim 10 , wherein the polishing slurry contains from about 6 to about 10% by weight of a colloidal silica abrasive.  
     
     
         13 . The process according to  claim 10 , wherein the polishing slurry contains from about 8 to about 15% by weight of a metal fluoride.  
     
     
         14 . The process according to  claim 4 , wherein the metal fluoride is selected from the group consisting of lithium fluoride, sodium fluoride and potassium fluoride.  
     
     
         15 . The process according to  claim 5 , wherein the metal fluoride is potassium fluoride.  
     
     
         16 . The process according to  claim 10 , wherein the process polishes a composite material which contains silica and silicon nitride.  
     
     
         17 . The process according to  claim 10 , wherein the pH at 22° C. of the polishing slurry is higher than about 10.5.  
     
     
         18 . The process according to  claim 10 , wherein the colloidal silica has a mean particle size ranging from about 10 nm to about 1 μm.  
     
     
         19 . In a shallow trench isolation process in which a trench is filled with SiO 2 , a wafer surface is covered with a film of silica and in which planarization is carried out with a chemical-mechanical polishing, the improvement comprising applying to the wafer surface at a temperature ranging from about 35° C. to about 80° C. a basic polishing slurry containing from 5 to 12.5% by weight of a colloidal silica abrasive and polishing the wafer surface.