Plasma generation and control using a dual frequency rf source

Abstract

A method and apparatus for generating and controlling a plasma in a semiconductor substrate processing chamber using a dual frequency RF source is provided. The method includes the steps of supplying a first RF signal from the source to an electrode within the processing chamber at a first frequency and supplying a second RF signal from the source to the electrode within the processing chamber at a second frequency. The second frequency is different from the first frequency by an amount equal to a desired frequency. Characteristics of a plasma formed in the chamber establish a sheath modulation at the desired frequency.

1 . Apparatus for etching a semiconductor substrate, comprising: 
 a first electrode located within a processing chamber; and    a dual frequency RF power source having a first output for supplying a first RF signal and a second output for supplying a second RF signal, the source adapted to establish a modulation of a plasma sheath at a desired frequency equal to the difference between the first and second RF signals.    
   
   
       2 . The apparatus of  claim 1 , further comprising: 
 a matching circuit having a common output coupled to the first electrode for matching the impedance of the first and second outputs of the RF source to the load in the chamber;    
   
   
       3 . The apparatus of  claim 1 , further comprising: 
 a second RF source coupled to a second electrode disposed in the chamber.    
   
   
       4 . The apparatus of  claim 1 , wherein the dual frequency RF power source is adapted to provide first and second RF signals for high frequency plasma excitation.  
   
   
       5 . The apparatus of  claim 1 , wherein the dual frequency RF power source is adapted to provide first and second RF signals for ion dissociation.  
   
   
       6 . The apparatus of  claim 1 , wherein the dual frequency RF power source is adapted to provide first and second RF signals centered about a desired high frequency for controlling a first set of plasma characteristics and separated by a quantity equal to a desired low frequency for controlling a second set of plasma characteristics.  
   
   
       4 . The apparatus of  claim 1 , further comprising: 
 a controller for controlling the dual frequency power source and having computer readable media containing a plurality of instructions that, when executed, cause the dual frequency RF power source to provide the first and second RF signals centered about a desired first frequency selected to control a first set of plasma characteristics and separated by a quantity equal to a desired second frequency for controlling a second set of plasma characteristics.    
   
   
       5 . Apparatus for plasma processing of a semiconductor substrate, comprising: 
 a processing chamber;    a substrate support pedestal disposed within the chamber;    a first electrode disposed within the pedestal;    a dual frequency RF power source coupled to the first electrode, the source adapted to supply a first and a second RF signal; and    a plasma formed in the chamber and having a plasma sheath, wherein the plasma sheath modulates at a desired frequency equal to the difference between the first and second RF signals.    
   
   
       6 . The apparatus of  claim 5 , further comprising: 
 a matching circuit having a common output coupled to the first electrode for matching the impedance of the first and second outputs of the RF source to the load in the chamber.    
   
   
       7 . The apparatus of  claim 5 , further comprising: 
 a second RF source coupled to a second electrode disposed in the chamber.    
   
   
       8 . The apparatus of  claim 5 , wherein the dual frequency RF power source is adapted to provide first and second RF signals for high frequency plasma excitation.  
   
   
       9 . The apparatus of  claim 5 , wherein the dual frequency RF power source is adapted to provide first and second RF signals for ion dissociation.  
   
   
       10 . The apparatus of  claim 5 , wherein the dual frequency RF power source is adapted to provide first and second RF signals centered about a desired high frequency for controlling a first set of plasma characteristics and separated by a quantity equal to a desired low frequency for controlling a second set of plasma characteristics.  
   
   
       11 . The apparatus of  claim 5 , further comprising: 
 a controller for controlling the dual frequency power source and having computer readable media containing a plurality of instructions that, when executed, cause the dual frequency RF power source to provide the first and second RF signals centered about a desired first frequency selected to control a first set of plasma characteristics and separated by a quantity equal to a desired second frequency for controlling a second set of plasma characteristics.    
   
   
       12 . Apparatus for plasma processing of a semiconductor substrate, comprising: 
 a processing chamber;    a substrate support pedestal disposed within the chamber;    a first electrode disposed within the pedestal;    a first RF power source coupled to the first electrode for supplying a first RF signal; and    a second RF power source coupled to the first electrode for supplying a second RF signal of about the same magnitude establish a modulation of a plasma sheath at a desired frequency equal to the difference between the first and second RF signals.    
   
   
       13 . The apparatus of  claim 12 , further comprising: 
 a matching circuit having a common output coupled to the first electrode for matching the impedance of the first and second outputs of the RF source to the load in the chamber.    
   
   
       14 . The apparatus of  claim 12 , further comprising: 
 a third RF source coupled to a second electrode disposed in the chamber.    
   
   
       15 . The apparatus of  claim 12 , wherein the first and second RF power sources are adapted to provide respective first and second RF signals centered about a desired high frequency for controlling a first set of plasma characteristics and separated by a quantity equal to a desired low frequency for controlling a second set of plasma characteristics.  
   
   
       16 . The apparatus of  claim 12 , further comprising: 
 a controller for controlling the dual frequency power source and having computer readable media containing a plurality of instructions that, when executed, cause the first and second RF power sources to provide the respective first and second RF signals centered about a desired first frequency selected to control a first set of plasma characteristics and separated by a quantity equal to a desired second frequency for controlling a second set of plasma characteristics.