Apparatus and method for controlling plasma uniformity in a semiconductor wafer processing system

Abstract

An apparatus and method for controlling a plasma in a plasma processing system. The apparatus comprises a wafer support pedestal surrounded by a process kit that is driven by an RF signal. Both an electrode (cathode) in the pedestal and the process kit are driven with an RF signal to establish a primary plasma above the pedestal and a secondary plasma above the process kit.

What is claimed is:  
     
         1 . Apparatus for controlling a plasma in a plasma processing system, comprising: 
 a wafer support pedestal;    a process kit surrounding said wafer support pedestal; and    an RF power supply coupled to said process kit.    
     
     
         2 . The apparatus of    claim 1    wherein said RF power supply is also coupled to said wafer support pedestal.  
     
     
         3 . The apparatus of    claim 1    further comprising a second RF power supply coupled to said wafer support pedestal.  
     
     
         4 . The apparatus of    claim 1    wherein said wafer support pedestal contains a chuck with a peripheral flange, said process kit is supported by said flange.  
     
     
         5 . The apparatus of    claim 4    wherein said process kit is supported in a spaced apart relationship with respect to said flange to form a gap therebetween.  
     
     
         6 . The apparatus of    claim 5    further comprising a cooling gas source coupled to said gap.  
     
     
         7 . The apparatus of    claim 1    wherein the wafer support pedestal comprises an annular electrode that is located beneath the process kit and said RF power supply is coupled to said annular electrode.  
     
     
         8 . A plasma processing system comprising: 
 a chamber;    a wafer support pedestal disposed within said chamber;    a process kit surrounding said wafer support pedestal; and    an RF power supply coupled to said process kit.    
     
     
         9 . The system of    claim 8    wherein said RF power supply is also coupled to said wafer support pedestal.  
     
     
         10 . The system of    claim 8    further comprising a second RF power supply coupled to said wafer support pedestal.  
     
     
         11 . The system of    claim 9    wherein said RF power supply provides a signal having a first frequency to said wafer support and a second signal having a second frequency to said process kit.  
     
     
         12 . The system of    claim 9    wherein said first and second frequencies are different.  
     
     
         13 . The system of    claim 11    wherein said process kit is supported in a spaced apart relationship with respect to said wafer support whereby a gap is formed therebetween.  
     
     
         14 . The system of    claim 12    wherein said gap defines a pathway for a cooling gas.  
     
     
         15 . The system of    claim 13    further comprising a cooling gas source that supplies said cooling gas to said gap.  
     
     
         16 . The apparatus of    claim 8    wherein the wafer support pedestal comprises an annular electrode that is located beneath the process kit and said RF power supply is coupled to said annular electrode.  
     
     
         17 . In a semiconductor wafer processing system, having a chamber containing a gas, in a semiconductor processing system having a chamber, a wafer support pedestal, a process kit and an RF power supply, a method for controlling a plasma uniformity comprising the steps of: 
 (a) supplying a first RF signal to the wafer support pedestal to produce a primary plasma; and    (b) supplying a second RF signal to the process kit to produce a secondary plasma.    
     
     
         18 . The method of    claim 17    wherein said first and second RF signals have the same frequency.  
     
     
         19 . The method of    claim 17    wherein said first and second RF signals have different frequencies.  
     
     
         20 . The method of    claim 19    wherein said first frequency is approximately 400 KHz to 200 MHz.  
     
     
         21 . The method of    claim 19    said second frequency is approximately 400 kHz to 60 MHz.  
     
     
         22 . The method of    claim 17    further comprising the step of 
 c) controlling a temperature of said process kit.  
 
     
     
         23 . A computer readable storage medium having program code embodied therein, said program code, when executed by a computer, for controlling a plasma in a semiconductor processing system having a chamber containing a gas, a wafer support pedestal, a process kit and an RF power supply, said program code controlling the semiconductor processing system in accordance with the following steps: 
 (a) supplying a first RF signal to the wafer support to produce a primary plasma; and    (b) supplying a second RF signal to the process kit to produce a secondary plasma.    
     
     
         24 . The computer readable storage medium of    claim 23    wherein said first and second RF signals have the same frequency.  
     
     
         25 . The computer readable storage medium of    claim 23    wherein said first and second RF signals have different frequencies.  
     
     
         26 . The computer readable storage medium of    claim 24    wherein said first frequency is approximately 400 kHz to 200 MHz.  
     
     
         27 . The computer readable storage medium of    claim 24    wherein said second frequency is approximately 400 kHz to 60 MHz.  
     
     
         28 . The computer readable storage medium of    claim 24    wherein said program comprises the further step of controlling a temperature of said process kit.  
     
     
         29 . Apparatus for supporting a semiconductor wafer, comprising: 
 a wafer support having a periphery;    a cathode electrode disposed centrally with respect to said wafer support; and    a secondary electrode, disposed within said wafer support, adjacent said periphery.    
     
     
         30 . The apparatus of    claim 29    wherein said wafer support is adapted to receive a process kit that surrounds said periphery.  
     
     
         31 . The apparatus of    claim 30    wherein said wafer support has a peripheral flange.  
     
     
         32 . The apparatus of    claim 30    wherein said electrode is situated proximate said peripheral flange beneath said process kit.