Etch chamber with dual frequency biasing sources and a single frequency plasma generating source

Abstract

A method and apparatus for selectively controlling a plasma in a processing chamber during wafer processing. The method includes providing process gasses into the chamber over a wafer to be processed, and providing high frequency RF power to a plasma generating element and igniting the process gases into the plasma. Modulated RF power is coupled to a biasing element, and wafer processing is performed according to a particular processing recipe. The apparatus includes a biasing element disposed in the chamber and adapted to support a wafer, and a plasma generating element disposed over the biasing element and wafer. A first power source is coupled to the plasma generating element, and a second power source is coupled to the biasing element. A third power source is coupled to the biasing element, wherein the second and third power sources provide a modulated signal to the biasing element.

1 . A method of processing a workpiece in a plasma reactor having electrode apparatus for coupling RF power to plasma in said reactor, said method comprising: 
 simultaneously applying RF power from three RF sources of three different RF frequencies to said electrode apparatus;    selecting respective power levels of said three RF sources to select respective characteristics of a plasma in said reactor.    
   
   
       2 . The method of  claim 1  wherein said electrode apparatus comprises a top electrode at a ceiling of the reactor and a bottom electrode at a wafer support of said reactor, and wherein the step of applying RF power comprises coupling first and second ones of said three RF sources to said bottom electrode.  
   
   
       3 . The method of  claim 2  wherein the step of applying RF power further comprises coupling a third one of said RF sources to said electrode apparatus.  
   
   
       4 . The method of  claim 3  wherein the step of coupling said third one of said RF sources to said electrode apparatus comprises coupling said third RF source to said top electrode.  
   
   
       5 . The method of  claim 1  wherein said respective characteristics comprise plasma ion density, plasma ion energy and wideness of energy band of said plasma ion energy.  
   
   
       6 . The method of  claim 1  wherein the frequencies of said first, second and third RF sources are VHF, HF and LF frequencies respectively.  
   
   
       7 . The method of  claim 6  wherein the step of selecting respective power levels comprises selecting the power levels of said first, second and third RF sources within respective predetermined ranges.  
   
   
       8 . A plasma reactor for processing a workpiece, comprising: 
 a reactor chamber and a wafer support within said chamber;    electrode apparatus for coupling RF power to plasma in said reactor;    three RF sources of three different RF frequencies coupled to said electrode apparatus.    
   
   
       9 . The reactor of  claim 8  wherein said three RF sources are independently controllable.  
   
   
       10 . The reactor of  claim 8  wherein said electrode apparatus comprises a top electrode at a ceiling location overlying said wafer support and a bottom electrode at said wafer support of said reactor.  
   
   
       11 . The reactor of  claim 10  wherein said first and second RF sources are coupled to said bottom electrode.  
   
   
       12 . The reactor of  claim 11  wherein said third RF sources is coupled to said top electrode.  
   
   
       13 . The reactor of  claim 8  further comprising first, second and third impedance match elements connected between said first, second and third RF sources, respectively, and said electrode apparatus.  
   
   
       14 . The method of  claim 8  wherein the frequencies of said first, second and third RF sources are VHF, HF and LF frequencies respectively.