Method and apparatus for local polishing control

Abstract

A method and apparatus for local polishing and deposition control in a process cell is generally provided. In one embodiment, an apparatus for electrochemically processing a substrate is provided that selectively polishes discrete conductive portions of a substrate by controlling an electrical bias profile across a processing area, thereby controlling processing rates between two or more conductive portions of the substrate.

1 . A polishing pad comprising:
 one or more electrodes formed in the polishing pad at or near a polishing surface of the polishing pad; and   a plurality of counter electrodes positioned at or near apertures in the polishing pad and electrically isolated from the one or more electrodes, wherein the apertures are adapted to facilitate the flow of polishing fluid, and wherein at least two of the plurality of counter electrodes are independently electrically bias able relative to the one or more electrodes.   
     
     
         2 . The polishing pad of  claim 1 , further including non-conducting elements formed in the polishing pad to provide the electrical isolation between the one or more electrodes and the plurality of counter electrodes. 
     
     
         3 . The polishing pad of  claim 1 , further including a wiring network connected to the one or more electrodes and the plurality of counter electrodes. 
     
     
         4 . The polishing pad of  claim 3 , further including:
 an electrical connector electrically connected to the wiring network and adapted to maintain electrical contact with the wiring network when the polishing pad is in motion.   
     
     
         5 . The polishing pad of  claim 4 , further including:
 a power source electrically connected to the electrical connector and adapted to selectively bias the one or more electrodes and the plurality of counter electrodes through the electrical connector and the wiring network.   
     
     
         6 . The polishing pad of  claim 1 , further including one or more grooves formed in the polishing surface of the polishing pad. 
     
     
         7 . The polishing pad of  claim 1 , wherein the plurality of counter electrodes are concentrically arranged. 
     
     
         8 . A method of using a chemical mechanical polishing (CMP) tool to perform electrochemical mechanical polishing (ECMP) of a substrate having metal formed thereon, the method comprising:
 introducing an electrolytic polishing fluid between the substrate and a polishing surface of a polishing pad having one or more electrodes formed at or near the polishing surface and a plurality of counter electrodes positioned at or near apertures in the polishing pad so as to establish an electrical circuit between the one or more electrodes, the metal, and the plurality of counter electrodes;   electrically biasing at least one of the plurality of counter electrodes at a different voltage potential from another of the plurality of counter electrodes relative to the one or more electrodes; and   pressing the substrate against the polishing surface while moving at least one of the polishing pad and the substrate.   
     
     
         9 . The method of  claim 8 , wherein moving at least one of the polishing pad and the substrate includes rotating at least one of the polishing pad and the substrate. 
     
     
         10 . The method of  claim 8 , wherein the voltage potential is proportional to a removal rate of metal. 
     
     
         11 . The method of  claim 10 , wherein the plurality of counter electrodes are concentrically arranged. 
     
     
         12 . The method of  claim 8 , further comprising measuring at least one of current or voltage potential differences between portions of the metal formed on the substrate. 
     
     
         13 . The method of  claim 12 , further comprising controlling the electrically biasing based on the measured potential differences. 
     
     
         14 . A polishing pad, comprising:
 a first counter electrode embedded in an insulator;   at least a second counter electrode embedded in the insulator; and   one or more electrodes formed in the polishing pad at or near a polishing surface of the polishing pad, wherein the polishing surface has a plurality of apertures exposing the first counter electrode and the second counter electrode, wherein the first and second counter electrodes are independently electrically bias able relative to the one or more electrodes.   
     
     
         15 . The polishing pad of  claim 14 , wherein the first counter electrode belongs to a first set of counter electrodes and the second counter electrode belongs to a second set of counter electrodes. 
     
     
         16 . The polishing pad of  claim 15 , wherein the first set of counter electrodes is disposed radially inward of the second set of counter electrodes. 
     
     
         17 . The polishing pad of  claim 14 , wherein the first and second counter electrodes are part of a plurality of counter electrodes arranged in a polar array.