RF Coil Plasma Generation

Abstract

Apparatus comprising a plasma chamber, a radio frequency (RF) power source, and a coil centrally disposed in the plasma chamber. The plasma chamber is configured to generate plasma that feeds a vacuum chamber adjacent the plasma chamber, and a first end of the coil is electrically coupled to the RF power source while a second end of the coil is electrically open.

1 . An apparatus, comprising:
 a plasma chamber configured to generate plasma that feeds a vacuum chamber adjacent the plasma chamber;   a radio frequency (RF) power source; and   a coil centrally disposed in the plasma chamber, wherein a first end of the coil is electrically coupled to the RF power source and a second end of the coil is electrically open.   
   
   
       2 . The apparatus of  claim 1  further comprising a conductor disposed between the coil's outer perimeter and an inner wall of the plasma chamber wherein the conductor is substantially parallel to a central axis of the coil and laterally separated from the coil's outer perimeter, and wherein the conductor is electrically biased at a predetermined potential. 
   
   
       3 . The apparatus of  claim 2  wherein the conductor is electrically grounded. 
   
   
       4 . The apparatus of  claim 2  wherein the conductor is laterally separated from the coil's outer perimeter by a distance ranging between about 0.25″ and about 10″. 
   
   
       5 . The apparatus of  claim 2  wherein the conductor is laterally separated from the coil's outer perimeter by a distance ranging between about 10% of the coil's outer diameter and about 100% of the coil's outer diameter. 
   
   
       6 . The apparatus of  claim 1  wherein the coil has a number of turns ranging between about 4 and about 200. 
   
   
       7 . The apparatus of  claim 1  wherein the coil has a wire thickness and a pitch, wherein the pitch is less than about 150% of the wire thiclkness. 
   
   
       8 . The apparatus of  claim 7  wherein the pitch is about 110% of the wire thickness. 
   
   
       9 . The apparatus of  claim 1  wherein the coil has a wire thickness ranging between about 0.001″ and about 0.25″. 
   
   
       10 . The apparatus of  claim 1  wherein the coil substantially comprises aluminum. 
   
   
       11 . The apparatus of  claim 1  wherein the RF power source is a first RF power source and the coil is a first coil, the apparatus further comprising:
 a second RF power source; and   a second coil smaller in diameter than the first coil and centrally disposed within the first coil's inner diameter, wherein a first end of the second coil is electrically coupled to the second RF power source and a second end of the second coil is electrically open.   
   
   
       12 . The apparatus of  claim 1  further comprising:
 a gas inlet coupled to the plasma chamber and configured to allow flow of a plasma source gas into the plasma chamber; and   a feedthrough coupled to one of the plasma chamber and the vacuum chamber, through which an RF signal from the RF power source external to the plasma and vacuum chambers is deliverable to the coil inside the plasma chamber through at least one electrical conductor extending between the feedthrough and the coil.   
   
   
       13 . The apparatus of  claim 1  further comprising the vacuum chamber. 
   
   
       14 . The apparatus of  claim 13  wherein the apparatus is an electron microscope. 
   
   
       15 . The apparatus of  claim 13  wherein the apparatus is a scanning electron microscope (SEM). 
   
   
       16 . A method of manufacturing an apparatus, comprising:
 disposing a coil centrally in a plasma chamber, wherein a first end of the coil is electrically open, and wherein the plasma chamber is configured to generate plasma that feeds into a vacuum chamber adjacent the plasma chamber; and   coupling a radio frequency (RF) power source to a second end of the coil.   
   
   
       17 . The method of  claim 16  further comprising disposing a conductor between the coil's outer perimeter and an inner wall of the plasma chamber, such that the conductor is substantially parallel to a central axis of the coil and laterally separated from the coil's outer perimeter, and wherein the conductor is configured to be electrically biased at a predetermined potential. 
   
   
       18 . The method of  claim 17  wherein the conductor is electrically grounded. 
   
   
       19 . The method of  claim 17  wherein the disposed conductor is laterally separated from the coil's outer perimeter by a distance ranging between about 0.25″ and about 10″. 
   
   
       20 . The method of  claim 17  wherein the disposed conductor is laterally separated from the coil's outer perimeter by a distance ranging between about 10% of the coil's outer diameter and about 100% of the coil's outer diameter. 
   
   
       21 . The method of  claim 16  wherein the coil has a number of turns ranging between about 4 and about 200. 
   
   
       22 . The method of  claim 16  wherein the coil has a wire thickness and a pitch, wherein the pitch is less than about 150% of the wire thickness. 
   
   
       23 . The method of  claim 22  wherein the pitch is about 110% of the wire thickness. 
   
   
       24 . The method of  claim 16  wherein the coil has a wire thickness ranging between about 0.001″ and about 0.25″. 
   
   
       25 . The method of  claim 16  wherein the coil substantially comprises aluminum. 
   
   
       26 . The method of  claim 16  wherein the RF power source is a first RF power source and the coil is a first coil, the method further comprising:
 disposing a second coil centrally within the first coil's inner diameter, wherein the second coil is smaller in diameter than the first coil and a first end of the second coil is electrically open; and   coupling a second RF power source to a second end of the second coil.   
   
   
       27 . The method of  claim 16  further comprising:
 establishing an electrical connection between the coil and a feedthrough coupled to one of the plasma chamber and the vacuum chamber, such that an RF signal from the RF power source external to the plasma and vacuum chambers is deliverable to the coil inside the plasma chamber.   
   
   
       28 . The method of  claim 16  further comprising coupling the plasma chamber to the vacuum chamber. 
   
   
       29 . The method of  claim 16  wherein the apparatus is an electron microscope. 
   
   
       30 . The method of  claim 16  wherein the apparatus is a scanning electron microscope (SEM). 
   
   
       31 . An apparatus, comprising:
 a vacuum chamber;   an emitter configured to emit a beam of at least one of ions and electrons into the vacuum chamber;   a plasma chamber coupled to the vacuum chamber;   means for supplying a plasma source gas into the plasma chamber;   a radio frequency (RF) power source; and   a coil located in a substantially central portion of the plasma chamber, wherein a first end of the coil is electrically coupled to the RF power source and a second end of the coil is electrically open.   
   
   
       32 . The apparatus of  claim 31  wherein the plasma source gas supplying means includes a flow controller configured to regulate pressure inside the plasma chamber. 
   
   
       33 . The apparatus of  claim 31  wherein the plasma source gas supplying means includes a valve configured to select between a plurality of different plasma source gas supplies. 
   
   
       34 . The apparatus of  claim 31  wherein the emitter includes a column configured to provide at least one of focusing and steering of the beam before the beam enters the vacuum chamber. 
   
   
       35 . The apparatus of  claim 31  further comprising a conductor disposed between the coil's outer perimeter and an inner wall of the plasma chamber, wherein the conductor is substantially parallel to a central axis of the coil and laterally separated from the coil's outer perimeter, and wherein the conductor is electrically biased at a predetermined potential. 
   
   
       36 . The apparatus of  claim 35  wherein the conductor is electrically grounded. 
   
   
       37 . The apparatus of  claim 35  wherein the conductor is laterally separated from the coil's outer perimeter by a distance ranging between about 0.25″ and about 10″. 
   
   
       38 . The apparatus of  claim 35  wherein the conductor is laterally separated from the coil's outer perimeter by a distance ranging between about 10% of the coil's outer diameter and about 100% of the coil's outer diameter. 
   
   
       39 . The apparatus of  claim 31  wherein the coil has a number of turns ranging between about 4 and about 200. 
   
   
       40 . The apparatus of  claim 31  wherein the coil has a wire thickness and a pitch, wherein the pitch is less than about 150% of the wire thiciness. 
   
   
       41 . The apparatus of  claim 40  wherein the pitch is about 110% of the wire thickness. 
   
   
       42 . The apparatus of  claim 31  wherein the coil has a wire thickness ranging between about 0.001″ and about 0.25″. 
   
   
       43 . The apparatus of  claim 31  wherein the coil substantially comprises aluminum. 
   
   
       44 . The apparatus of  claim 31  wherein the RF power source is a first RF power source and the coil is a first coil, the apparatus further comprising:
 a second RF power source; and   a second coil centrally located within the first coil, wherein a first end of the second coil is electrically coupled to the second RF power source and a second end of the second coil is electrically open.   
   
   
       45 . The apparatus of  claim 31  wherein the apparatus is an electron microscope. 
   
   
       46 . The apparatus of  claim 31  wherein the apparatus is a scanning electron microscope (SEM).