RF Plasma Source With Conductive Top Section

Abstract

A plasma source includes a chamber that contains a process gas. The chamber has a chamber top comprising a first section formed of a dielectric material that extends in a horizontal direction. A second section of the chamber top is formed of a dielectric material that extends a height from the first section in a vertical direction. A top section of the chamber top is formed of a conductive material that extends a length across the second section in the horizontal direction. A radio frequency antenna is positioned proximate to at least one of the first section and the second section. The radio frequency antenna induces radio frequency currents into the chamber that excite and ionize the process gas so as to generate a plasma in the chamber.

1 . A plasma source comprising: 
 a chamber that contains a process gas, the chamber having a chamber top comprising: a first section formed of a dielectric material that extends in a horizontal direction; a second section formed of a dielectric material that extends a height from the first section in a vertical direction; and a top section formed of a conductive material that extends a length across the second section in the horizontal direction; and    a radio frequency antenna that is positioned proximate to at least one of the first section and the second section, the radio frequency antenna inducing radio frequency currents into the chamber that excite and ionize the process gas so as to generate a plasma in the chamber.    
   
   
       2 . The plasma source of  claim 1  wherein a ratio of the height from the first section in the vertical direction to the length across the second section in the horizontal direction is approximately between 1.5 and 5.5.  
   
   
       3 . The plasma source of  claim 1  wherein the radio frequency antenna comprises a planar coil that is positioned proximate to the first section.  
   
   
       4 . The plasma source of  claim 1  wherein the radio frequency antenna comprises a coil that surrounds the second section.  
   
   
       5 . The plasma source of  claim 1  wherein the radio frequency antenna comprises a planar coil that is positioned adjacent to the first section and a coil that surrounds the second section.  
   
   
       6 . The plasma source of  claim 5  wherein the planar coil that is positioned adjacent to the first section and the coil that surrounds the second section are electrically connected.  
   
   
       7 . The plasma source of  claim 5  wherein the planar coil that is positioned adjacent to the first section and the coil that surrounds the second section are positioned in electromagnetic communication.  
   
   
       8 . The plasma source of  claim 1  wherein the radio frequency antenna comprises an active antenna that is electrically coupled to a radio frequency power supply and a parasitic antenna that is electromagnetically coupled to the active antenna.  
   
   
       9 . The plasma source of  claim 8  wherein one end of the parasitic antenna is electrically coupled to ground potential.  
   
   
       10 . The plasma source of  claim 1  wherein the top section comprises a fluid cooling system that regulates a temperature of the top section.  
   
   
       11 . The plasma source of  claim 1  wherein the chamber top is electrically connected to ground potential.  
   
   
       12 . The plasma source of  claim 1  further comprising a platen for holding a target that is positioned adjacent to the top section.  
   
   
       13 . The plasma source of  claim 12  further comprising a bias voltage power supply having an output that is electrically connected to the platen, the bias voltage power supply generating a voltage on the platen that attracts ions in the plasma to the target.  
   
   
       14 . A plasma source comprising: 
 a chamber that contains a process gas, the chamber having a chamber top comprising: a first section formed of a dielectric material that extends in a first direction; a second section formed of a dielectric material that extends a height from the first section in a second direction; and a top section formed of a conductive material that extends a length across the second section; and    a radio frequency antenna that is positioned proximate to at least one of the first section and the second section, the radio frequency antenna inducing radio frequency currents into the chamber that excite and ionize the process gas so as to generate a plasma in the chamber.    
   
   
       15 . The plasma source of  claim 14  wherein the first section is curved.  
   
   
       16 . The plasma source of  claim 14  wherein the first and second directions are not orthogonal.  
   
   
       17 . A method of generating a uniform plasma, the method comprising: 
 introducing a process gas into a chamber;    inducing a radio frequency current through at least one of a horizontal dielectric window and a vertical dielectric window of the chamber, the radio frequency current exciting and ionizing the process gas so as to generate a plasma in the chamber; and    biasing a target so that ions in the plasma are attracted to the target, wherein secondary electrons generated when the ions hit the target are dissipated by a top section of the chamber that is formed of a conductive material, thereby reducing charging effects and improving a uniformity of the plasma.    
   
   
       18 . The method of  claim 17  further comprising cooling the top section of the chamber to dissipate heat generated when the secondary electrons hit the target.  
   
   
       19 . A method of generating a uniform plasma, the method comprising: 
 introducing a process gas into a chamber;    inducing a radio frequency current through one of a horizontal dielectric window and a vertical dielectric window of the chamber, the radio frequency current exciting and ionizing the process gas so as to generate a plasma in the chamber;    electromagnetically coupling the induced radio frequency current from the one of the horizontal dielectric window and the vertical dielectric window to the other of the horizontal dielectric window and the vertical dielectric window; and    biasing a target so that ions in the plasma are attracted to the target, wherein secondary electrons generated when the ions hit the target are dissipated by a top section of the chamber that is formed of a conductive material, thereby reducing charging effects and improving a uniformity of the plasma.    
   
   
       20 . The method of  claim 19  further comprising adjusting the electromagnetic coupling to improve the uniformity of the plasma.  
   
   
       21 . A plasma source comprising: 
 a chamber that contains a process gas, the chamber having a chamber top comprising: a first section formed of a dielectric material that extends in a horizontal direction; a second section formed of a dielectric material that extends a height from the first section in a vertical direction; and a top section formed of a conductive material that extends a length across the second section in the horizontal direction;    an anode that is positioned in the chamber adjacent to the top section; and    a radio frequency antenna that is positioned proximate to at least one of the first section and the second section, the radio frequency antenna inducing radio frequency currents into the chamber that excite and ionize the process gas so as to generate a plasma in the chamber.    
   
   
       22 . The plasma source of  claim 21  wherein the position of the anode in the chamber relative to the top section is adjustable.  
   
   
       23 . The plasma source of  claim 21  wherein the position of the anode in the chamber relative to the top section is chosen to achieve a predetermined plasma uniformity.  
   
   
       24 . The plasma source of  claim 21  wherein a ratio of an area of the anode to an area of the top section is less than one.  
   
   
       25 . The plasma source of  claim 21  wherein the anode comprises a baffle that disperses the process gas.  
   
   
       26 . The plasma source of  claim 21  wherein the anode comprises a shower head that dispenses the process gas.  
   
   
       27 . The plasma source of  claim 21  wherein the anode is electrically connected to ground potential.  
   
   
       28 . A method of generating a plasma, the method comprising: 
 introducing a process gas into a chamber;    biasing an anode that is positioned in the chamber to emit electrons from the anode;    inducing a radio frequency current through a horizontal dielectric window of the chamber; and    inducing a radio frequency current through a vertical dielectric window of the chamber, wherein at least one of the electrons emitted by the anode and the induced radio frequency currents exciting and ionizing the process gas to ignite a plasma in the chamber.    
   
   
       29 . The method of  claim 28  wherein the biasing the anode comprises applying a pulsed direct current to the anode.  
   
   
       30 . The method of  claim 28  wherein the biasing the anode comprises applying a RF field to the anode.  
   
   
       31 . The method of  claim 28  wherein the biasing the anode comprises applying a combination of pulsed DC and RF signals.  
   
   
       32 . The method of  claim 28  further comprising sustaining the plasma with the induced radio frequency currents.  
   
   
       33 . The method of  claim 28  further comprising sustaining the plasma with the electrons generated from the anode.