Chemical mechanical polishing method for tungsten

Abstract

A process for chemical mechanical polishing a substrate containing tungsten is disclosed to reduce corrosion rate and inhibit dishing of the tungsten and erosion of underlying dielectrics. The process includes providing a substrate; providing a polishing composition, containing, as initial components: water; an oxidizing agent; nonionic polyacrylamide; a dicarboxylic acid, a source of iron ions; a colloidal silica abrasive having a negative zeta potential; and, optionally, a pH adjusting agent; providing a chemical mechanical polishing pad, having a polishing surface; creating dynamic contact at an interface between the polishing pad and the substrate; and dispensing the polishing composition onto the polishing surface at or near the interface between the polishing pad and the substrate; wherein some of the tungsten is polished away from the substrate, corrosion rate is reduced, dishing of the tungsten is inhibited as well as erosion of dielectrics underlying the tungsten.

1 - 8 . (canceled) 
     
     
         9 . A composition for chemical mechanical polishing tungsten consisting of, as initial components:
 water;
 an oxidizing agent; 
 nonionic polyacrylamide 
 a colloidal silica abrasive having a negative zeta potential; 
 a dicarboxylic acid, salt thereof or mixtures thereof, 
 a source of iron (III) ions; and, 
 optionally, a pH adjusting agent. 
   
     
     
         10 . The composition of  claim 9 , wherein the chemical mechanical polishing composition for tungsten consists of, as initial components:
 the water;   0.01 to 10 wt % of the oxidizing agent, wherein the oxidizing agent is hydrogen peroxide;   20 to 320 ppm of the nonionic polyacrylamide;   0.01 to 10 wt % of the colloidal silica abrasive having a negative zeta potential;   100 to 1,400 ppm of the dicarboxylic acid, salt thereof or mixtures thereof, wherein the dicarboxylic acid, salt thereof or mixtures thereof is malonic acid, salt thereof or mixtures thereof;   100 to 1,000 ppm of the source of iron (III) ions, wherein the source of iron (III) ions is ferric nitrate nonahydrate; and   optionally the pH adjusting agent; wherein the chemical mechanical polishing composition has a pH from 1 to 7.   
     
     
         11 . The composition of  claim 9 , wherein the chemical mechanical polishing composition for tungsten consists of, as initial components:
 the water;   1 to 3 wt % of the oxidizing agent, wherein the oxidizing agent is hydrogen peroxide;   50 to 320 ppm of the nonionic polyacrylamide;   0.2 to 2 wt % of the colloidal silica abrasive having a negative zeta potential;   120 to 1,350 ppm of the dicarboxylic acid, salt thereof or mixtures thereof, wherein the dicarboxylic acid, salt thereof or mixtures thereof is malonic acid, salt thereof or mixtures thereof;   250 to 400 ppm of the source of iron (III) ions, wherein the source of iron (III) ions is ferric nitrate nonahydrate; and   optionally the pH adjusting agent; wherein the chemical mechanical polishing composition has a pH from 2 to 2.5.