Methods for Selectively Modifying RF Current Paths in a Plasma Processing System

Abstract

Methods and apparatus for modifying RF current path lengths are disclosed. Apparatus includes a plasma processing system having an RF power supply and a lower electrode having a conductive portion. There is included an insulative component disposed in an RF current path between the RF power supply and the conductive portion. There are included a plurality of RF path modifiers disposed within the insulative component, the plurality of RF path modifiers being disposed at different angular positions relative to a reference angle drawn from a center of the insulative component, whereby at least a first one of the plurality of RF path modifiers is electrically connected to the conductive portion and at least a second one of the plurality of the plurality of RF path modifiers is not electrically connected to the conductive portion.

What is claimed is: 
     
         1 . A method for compensating for azimuthal non-uniformity in a plasma processing system having a plasma processing chamber, comprising:
 measuring, using at least one sensor associated with said chamber, indicia of said azimuthal non-uniformity; and   adjusting, responsive to said measuring, by selectively connecting a first RF path modifier of a plurality of RF path modifiers to a conductive portion of a lower electrode, whereby at least a second RF path modifier of said plurality of RF path modifiers is not connected to said conductive portion of said lower electrode after said adjusting and wherein said plurality of RF path modifiers are disposed in an insulator portion that is disposed in an RF current path between an RF current source and said conductive portion.   
     
     
         2 . The method of  claim 1 , wherein said RF path modifiers are implemented using conductive plugs. 
     
     
         3 . The method of  claim 1 , wherein said RF path modifiers are implemented using impedance devices. 
     
     
         4 . A method for compensating for azimuthal non-uniformity in a plasma processing system having a plasma processing chamber, comprising:
 measuring, using at least one sensor associated with said chamber, indicia of said azimuthal non-uniformity; and   adjusting, responsive to said measuring, by adjusting an impedance value of at least a first RF path modifier of a plurality of RF path modifiers to a first impedance value, whereby at least a second impedance value of a second RF path modifier of said plurality of RF path modifiers is different from said first impedance value after said adjusting and wherein said plurality of RF path modifiers are disposed in an insulator portion that is disposed in an RF current path between an RF current source and a conductive portion of a lower electrode in said plasma processing chamber.   
     
     
         5 . The method of  claim 4 , wherein said adjusting is performed automatically in-situ in response to computer readable instructions from computer. 
     
     
         6 . The method of  claim 4 , wherein said plurality of RF path modifiers are implemented using impedance devices, each of said impedance devices includes at least one of a capacitor and an inductor. 
     
     
         7 . A method for compensating for azimuthal non-uniformity in a plasma processing system having a plasma processing chamber, comprising:
 measuring, using at least one sensor associated with said chamber, indicia of said azimuthal non-uniformity; and   adjusting, responsive to said measuring, by selectively adjusting one or more of RF path modifiers of a plurality of RF path modifiers conductively coupled to a conductive portion of a lower electrode and wherein said plurality of RF path modifiers are disposed in an insulator portion that is disposed in an RF current path between an RF current source and said conductive portion, and each of the plurality of RF path modifiers is individually adjustable to define an intentional non-symmetric impedance at different locations around the lower electrode to compensate for measured indicia of said azimuthal non-uniformity in the plasma processing system.   
     
     
         8 . The method of  claim 7 , wherein the selectively adjusting is by connecting one or more of the RF path modifiers to the conductive portion of the lower electrode. 
     
     
         9 . The method of  claim 8 , wherein the adjusting is performed automatically in-situ responsive to computer readable instructions from a computer. 
     
     
         10 . The method of  claim 7 , wherein said lower electrode is an electrostatic chuck. 
     
     
         11 . The method of  claim 7 , wherein said plurality of RF path modifiers are implemented using machine tunable impedance devices, each of said impedance devices includes at least one of a capacitor and an inductor, wherein impedance value of each of said plurality of RF path modifiers is settable via at least one electrical control signal. 
     
     
         12 . The method of  claim 7 , wherein impedance values of said plurality of RF modifiers are set by machine tunable impedance devices in-situ on a wafer-by-wafer basis or for a plurality of wafers before processing in response to one or more sensor measurements. 
     
     
         13 . The method of  claim 7 , wherein impedance values of said plurality of RF modifiers are automatically tuned by machine tunable impedance devices in-situ at least on a wafer-by-wafer basis during production in response to sensor measurements that indicate manipulation of RF return currents may be needed to address azimuthal non-uniformity issues. 
     
     
         14 . The method of  claim 7 , wherein said plurality of RF path modifiers are implemented using impedance devices, each of said impedance devices includes at least one of a capacitor and an inductor. 
     
     
         15 . The method of  claim 7 , wherein said plurality of RF path modifiers are disposed at regular angular intervals relative to a reference angle. 
     
     
         16 . The method of  claim 7 , wherein said plurality of RF path modifiers are implemented using conductive plugs.