Magnetic focus rings for improved copper plating

Abstract

A method and system wherein magnets are employed on the outside of a plating bath chamber to control the field lines that are used during the plating process. By being able to control the field lines during the plating process, improved gap fill and uniformity can be achieved. The magnetic field acting on the bath can be continuous, pulsed, stressed (i.e., the shape of the field can be changed), sinusoidal, etc. The magnetic field can be modulated as function of time to produce a desired copper uniformity on the wafer. It is anticipated that there is no limit to how the shape of the magnets or magnetic field can be configured and controlled to achieve the desired result for both fill of deep contacts and the uniformity needed to match the succeeding polishing process.

1 . A method for using an anode to plate a cathode with ions in a bath chamber, comprising: applying a voltage to the anode and the cathode, the anode and cathode being disposed in the bath chamber, thereby causing ions to flow along field lines from the anode to the cathode in the bath chamber and plate the cathode; and using at least one magnet to adjust the field lines.  
     
     
         2 . A method as recited in  claim 1 , wherein the anode comprises copper and the cathode comprises a wafer.  
     
     
         3 . A method as recited in  claim 1 , wherein the step of using at least one magnet to adjust the field lines comprises using a plurality of permanent magnets.  
     
     
         4 . A method as recited in  claim 1 , wherein the step of using at least one magnet to adjust the field lines comprises using a plurality of electro-magnets.  
     
     
         5 . A method as recited in  claim 1 , wherein the step of using at least one magnet to adjust the field lines comprises using a control system and a plurality of electro-magnets connected to the control system.  
     
     
         6 . A method as recited in  claim 1 , wherein the step of using at least one magnet to adjust the field lines comprises using a plurality of magnets which are disposed outside of the bath chamber.  
     
     
         7 . A method as recited in  claim 1 , wherein the step of using at least one magnet to adjust the field lines comprises using a plurality of magnets which are disposed outside of the bath chamber, around a circumference of the bath chamber.  
     
     
         8 . A method as recited in  claim 1 , wherein the step of using at least one magnet to adjust the field lines comprises using a plurality of magnets and controlling the magnets such that the magnets provide a magnetic field which is at least one of continuous, pulsed, stressed and sinusoidal.  
     
     
         9 . A method as recited in  claim 1 , wherein the step of using at least one magnet to adjust the field lines comprises using a plurality of magnets and controlling the magnets such that the magnets provide a magnetic field which is modulated over time.  
     
     
         10 . A plating system comprising: a bath chamber; an anode disposed in the bath chamber; a cathode disposed in the bath chamber; a voltage source connected to the anode and cathode, wherein application of voltage causes ions to flow along field lines from the anode to the cathode in the bath chamber and plate the cathode; and at least one magnet disposed proximate the bath chamber, wherein said at least one magnet adjusts the field lines.  
     
     
         11 . A system as recited in  claim 10 , wherein the anode comprises copper and the cathode comprises a wafer.  
     
     
         12 . A system as recited in  claim 10 , wherein said at least one magnet comprises a plurality of permanent magnets.  
     
     
         13 . A system as recited in  claim 10 , wherein said at least one magnet comprises a plurality of electro-magnets.  
     
     
         14 . A system as recited in  claim 13 , further comprising a control system connected to the plurality of electro-magnets.  
     
     
         15 . A system as recited in  claim 10 , wherein said at least one magnet comprises a plurality of magnets which are disposed outside of the bath chamber.  
     
     
         16 . A system as recited in  claim 10 , wherein said at least one magnet comprises a plurality of magnets which are disposed outside of the bath chamber, around a circumference of the bath chamber.  
     
     
         17 . A system as recited in  claim 14 , wherein the control system is configured to control the electro-magnets such that the electro-magnets provide a magnetic field which is at least one of continuous, pulsed, stressed and sinusoidal.  
     
     
         18 . A system as recited in  claim 14 , wherein the control system is configured to control the electro-magnets such that the electro-magnets provide a magnetic field which is modulated over time.