Process using combined capacitively and inductively coupled plasma process for controlling plasma ion dissociation

Abstract

A method of processing a workpiece in the chamber of a plasma reactor includes introducing a process gas into the chamber, simultaneously (a) capacitively coupling VHF plasma source power into a process region of the chamber that overlies the wafer, and (b) inductively coupling RF plasma source power into the process region, and adjusting the extent of dissociation of species in the plasma by adjusting the ratio between the amounts of the capacitively coupled VHF power and the inductively coupled power. The method may further include controlling plasma ion density in the chamber by controlling the total amount of plasma source power capacitively and inductively coupled into the process region.

1 . A method of processing a workpiece in the chamber of a plasma reactor, comprising: 
 introducing a process gas into the chamber;    simultaneously (a) capacitively coupling VHF plasma source power into a process region of the chamber that overlies the wafer, and (b) inductively coupling RF plasma source power into said process region;    adjusting the extent of dissociation of species in the plasma by adjusting the ratio between the amounts of said capacitively coupled VHF power and said inductively coupled power.    
   
   
       2 . The method of  claim 1  further comprising: 
 controlling plasma ion density in the chamber by controlling the total amount of plasma source power capacitively and inductively coupled into said process region.    
   
   
       3 . The method of  claim 2  wherein said ratio is adjusted along a line of constant plasma density.  
   
   
       4 . The method of  claim 1  further comprising applying independently adjustable LF bias power and HF bias power to said workpiece; and  
   
   
       5 . The method of  claim 4  further comprising adjusting the average value and population distribution of ion energy at the surface of said workpiece by adjusting the ratio between said LF and HF bias powers.  
   
   
       6 . The method of  claim 2  wherein the control of plasma ion density and the adjustment of dissociation are performed substantially independently of one another.  
   
   
       7 . The method of  claim 1  further comprising further adjusting the extent of dissociation of species in the plasma by adjusting the effective frequency of said capacitively coupled VHF source power.  
   
   
       8 . The method of  claim 7  wherein the adjusting of the effective frequency of said capacitively coupled VHF source power comprises adjusting the ratio between the output power levels of a pair of VHF power generators having different fixed frequencies and coupled to deliver VHF power to said process region.  
   
   
       9 . The method of  claim 1  wherein the step of adjusting said ratio comprises: 
 adjusting the power levels of said capacitively coupled RF plasma source power and said inductively coupled RF plasma source power.    
   
   
       10 . The method of  claim 1  wherein the step of adjusting said ratio comprises: 
 pulsing at least said inductively coupled RF plasma source power and adjusting the ratio between the duty cycles of said inductively coupled plasma source power and said capacitively coupled plasma source power.    
   
   
       11 . The method of  claim 1  further comprising adjusting the chemical species content of plasma in said process region by adjusting the residency time of said process gas in said chamber.  
   
   
       12 . The method of  claim 11  wherein the step of adjusting the chemical species content comprises adjusting an evacuation rate of process gas in said chamber.  
   
   
       13 . The method of  claim 11  wherein the step of adjusting the residency time comprises adjusting a distance between said workpiece and a ceiling of said chamber.  
   
   
       14 . The method of  claim 1  wherein the step of introducing a process gas comprises introducing the process gas through an overhead gas distribution showerhead having plural gas inlet orifices, said method further comprising: 
 limiting the distance between said workpiece and said gas distribution showerhead so that a gas distribution pattern of said plural gas inlet orifices affects plasma distribution at said workpiece.    
   
   
       15 . The method of  claim 2  wherein said workpiece comprises a multi-layer thin film structure comprising different materials in different layers of said structure, and wherein said method is employed to etch successive ones of said different layers in different plasma process conditions, said method further comprising: 
 repeating the step of adjusting whenever said method causes a successive one of said layers to be exposed, whereby to customize plasma process conditions for each of said different layers.    
   
   
       16 . The method of  claim 1  wherein said ratio is adjusted to maximize plasma ion radial distribution uniformity.  
   
   
       17 . The method of  claim 1  wherein said ratio is adjusted by changing said inductively coupled and capacitively coupled power levels along lines of constant plasma density.  
   
   
       18 . The method of  claim 10  wherein said ratio is adjusted by changing said inductively coupled and capacitively coupled power duty cycles along lines of constant plasma density.  
   
   
       19 . The method of  claim 5  wherein the step of adjusting the average value and population distribution of ion energy comprises adjusting the effective frequency of said HF bias power to change the ion population distribution about an intermediate energy.  
   
   
       20 . The method of  claim 5  wherein the step of adjusting the average value and population distribution of ion energy comprises adjusting the effective frequency of said LF bias power to change the ion population distribution about a maximum energy.  
   
   
       21 . The method of  claim 1  wherein said VHF power is capacitively coupled through one or both of said ceiling and said wafer support.  
   
   
       22 . The method of  claim 1  wherein the step of capacitively coupled RF source power into said process region comprises capacitively coupling VHF power from both a ceiling of said chamber and a wafer support of said chamber simultaneously, said method comprising: 
 performing a further adjustment of the radial distribution of plasma ion density by adjusting the difference between the phase of VHF voltage or current at the ceiling and the phase of VHF voltage or current at the wafer support.