Generation of uniformly-distributed plasma

Abstract

Methods and apparatus for generating uniformly-distributed plasma are described. A plasma generator according to the invention includes a cathode assembly that is positioned adjacent to an anode and forming a gap there between. A gas source supplies a volume of feed gas and/or a volume of excited atoms to the gap between the cathode assembly and the anode. A power supply generates an electric field across the gap between the cathode assembly and the anode. The electric field ionizes the volume of feed gas and/or the volume of excited atoms that is supplied to the gap, thereby creating a plasma in the gap.

1 - 53 . (canceled)  
     
     
         54 . A plasma generator comprising: 
 a. an anode;    b. a cathode assembly that is positioned adjacent to the anode;    c. an excited atom source that generates at least one of excited atoms and excited molecules from a feed gas, the excited atom source supplying the at least one of excited atoms and excited molecules to the cathode assembly; and    d. a power supply that generates a pulsed electric field across the cathode assembly and the anode that ionizes the at least one of the excited atoms and excited molecules that are supplied to the cathode assembly by the excited atom source, at least one of a shape and a duration of at least one of a leading edge and a trailing edge of the pulsed electric field controlling a rate of ionization of the plasma.    
     
     
         55 . The plasma generator of  claim 54  wherein the cathode assembly comprises a target.  
     
     
         56 . The plasma generator of  claim 54  wherein the power supply generates a constant power.  
     
     
         57 . The plasma generator of  claim 54  wherein the power supply generates a constant voltage.  
     
     
         58 . The plasma generator of  claim 54  further comprising a magnet assembly that generates a magnet field that substantially traps electrons in the plasma.  
     
     
         59 . The plasma generator of  claim 54  wherein the cathode assembly comprises a hollow cathode comprising an inner surface that substantially surrounds the anode.  
     
     
         60 . The plasma generator of  claim 59  wherein the inner surface comprises a cylindrical wall.  
     
     
         61 . The plasma generator of  claim 54  wherein the plasma is substantially uniformly-distributed proximate to a surface of the cathode assembly.  
     
     
         62 . The plasma generator of  claim 54  wherein a peak plasma density of the plasma is in the range of about 10 7  cm −3  to 10 16  cm −1 .  
     
     
         63 . A plasma generator comprising: 
 a. an anode;    b. a cathode assembly that is positioned adjacent to the anode;    c. a gas source that supplies feed gas to the cathode assembly;    d. an excited atom source that generates at least one of excited atoms and excited molecules from feed gas supplied by the gas source, the excited atom source supplying the at least one of excited atoms and excited molecules to the cathode assembly; and    e. a power supply that generates an electric field across the cathode assembly and the anode, the electric field ionizing the at least one of excited atoms and excited molecules, thereby creating a plasma.    
     
     
         64 . The plasma generator of  claim 63  wherein a flow rate of the feed gas that is supplied to the cathode assembly from the gas source is chosen to increase a density of the plasma proximate to a surface of the cathode assembly.  
     
     
         65 . The plasma generator of  claim 63  wherein a flow rate of the feed gas that is supplied to the cathode assembly is chosen to increase uniformity of the plasma proximate to the surface of the cathode assembly.  
     
     
         66 . A method for generating a plasma, the method comprising: 
 a. generating at least one of excited atoms and excited molecules from a feed gas;    b. supplying the at least one of the excited atoms and excited molecules to a cathode assembly; and    c. applying a pulsed electric field across the cathode assembly and the anode, the pulsed electric field ionizing the at least one of the exited atoms and excited molecules, thereby creating a plasma; and    d. selecting at least one of a shape and a duration of at least one of a leading edge and a trailing edge of the pulsed electric field to control a rate of ionization of the plasma.    
     
     
         67 . The method of  claim 66  wherein the applying the pulsed electric field comprises applying the pulsed electric field at a constant power.  
     
     
         68 . The method of  claim 66  wherein the applying the pulsed electric field comprises applying the pulsed electric field at a constant voltage.  
     
     
         69 . The method of  claim 66  further comprising generating a magnetic field proximate to the plasma, the magnetic field trapping electrons in the plasma, thereby increasing the density of the plasma.  
     
     
         70 . The method of  claim 66  further comprising adjusting a flow rate of the feed gas to increase a density of the plasma.  
     
     
         71 . The method of  claim 66  further comprising adjusting a flow rate of the feed gas to increase plasma uniformity of the plasma proximate to a surface of the cathode assembly.  
     
     
         72 . The method of  claim 66  wherein a repetition rate of the pulsed electric field is in the range of about 0.1 Hz to 10 kHz.  
     
     
         73 . The method of  claim 66  wherein a magnitude of the pulsed electric field is chosen to reduce a probability of establishing an electrical breakdown condition leading to an undesirable electrical discharge.