Ceric-ion slurry for use in chemical-mechanical polishing

Abstract

The invention provides a chemical-mechanical polishing slurry comprising a liquid, cerium ions as an oxidizer, an abrasive, and a pH increasing substance. The cerium ions are in the liquid in a quantity equal to the inclusion of at least 0.02 molar ammonium cerium nitrate in the liquid. The abrasive is also included in the liquid. The liquid, the cerium ions and the abrasive jointly have a first pH value. The pH increasing substance increases the first pH value to a second pH value above 1.5.

1 - 20 . (canceled)  
     
     
         21 . A method of forming a metal line, comprising: 
 forming a first layer, with an opening therein, over a semiconductor substrate;    depositing a metal layer which fills the opening and covers the first layer;    applying a chemical-mechanical polishing slurry onto the metal layer, the slurry comprising cerium ions as an oxidizer, and an abrasive;    contacting a polishing surface against the metal layer; and    moving the polishing surface over the metal layer.    
     
     
         22 . The method of  claim 21  wherein the slurry comprises cerium ions in quantity sufficient to oxidize a portion of the metal layer, and the abrasive in quantity sufficient to assist in removal of the oxidized portion when the polishing surface is moved over the metal layer.  
     
     
         23 . The method of  claim 21  wherein the metal layer is of a metal selected from the group consisting of copper and tungsten.  
     
     
         24 . The method of  claim 21  further comprising: 
 depositing a barrier layer over the first layer and before depositing the metal layer, the cerium ions selectively oxidizing the material of the metal layer over the material of the barrier layer.  
 
     
     
         25 . The method of  claim 21  wherein the metal layer is removed at a rate of at least 1000 angstroms per minute.