Method and apparatus to eliminate contaminant particles from an accelerated neutral atom beam and thereby protect a beam target

Abstract

An improved ANAB system or process substantially or fully eliminating contaminant particles from reaching a beam target by adding to the usual primary (first) ionizer of the ANAB system or process an additional (second) ionizer to ionize contaminant particles and means to block or retard the ionized particles to prevent their reaching the beam target.

What is claimed is: 
     
         1 . A method of processing a substrate target surface for one or more of etching, smoothing planarization or other modification of the substrate target surface, comprising the steps of:
 (a) forming gas cluster ions by a primary (first) ionization step in a reduced pressure ambient in a chamber,   (b) accelerating the gas cluster ions to form an accelerated gas cluster ion beam (GCIB) along a beam path within the chamber,   (c) promoting fragmentation and/or disassociation of at least a portion of the gas clusters along the beam path toward a substrate to be processed,   (d) removing charged particles from the beam path to form an accelerated neutral beam, and   (e) providing an assembly for deflecting or blocking contaminant particles such that no paths to a substrate to be processed exist other than through the assembly.   
     
     
         2 . The method of  claim 1  wherein the step of deflecting or blocking includes a secondary electron ionization step which is operated without detrimentally influencing the primary ionization by employing positive offset voltages and a surrounding ground screen to prevent electrons from escaping. 
     
     
         3 . The improved method of  claim 2  wherein a retarding field is employed in the assembly to block ionized particles from travelling to the target substrate surface. 
     
     
         4 . The improved method of  claim 2  wherein an electrostatic deflector is employed in the assembly to remove ionized particles from the path to the target substrate surface. 
     
     
         5 . A method of controlling the flow path of a beam of desired neutral monomer particles with contaminant neutral particles therein, with said two types of particles differing by at least one order of magnitude of speed and/or of size, by providing an ionization condition in the flow path that substantially ionizes the contaminant neutral particles of larger size and/or slower speed, and substantially fails to ionize desired neutral monomer particles of smaller size and/or higher speed than the desired particles of the neutral beam and providing a deflection or retarding step to enable separation of the ionized contaminant particles from the un-ionized neutral particles. 
     
     
         6 . An ANAB apparatus for treating a target substrate surface by neutral monomer beams comprising:
 a contaminant particle elimination assembly positioned in an ANAB system wherein generates a gas cluster ion beam with a primary ionizer and acceleration and means to direct the accelerated beam on a path to the target substrate surface, the assembly being within or affecting the beam path such that no paths exist to the target substrate surface other than through the assembly, the assembly being constructed and arranged to eliminate the contaminant particles.   
     
     
         7 . The apparatus of  claim 6  comprising:
 a secondary electron impact ionizer in the assembly constructed and arranged to ionize contaminant particles in the beam without detrimentally influencing the primary ionization by employing positive offset voltages and a surrounding ground screen to prevent electrons from escaping. 
 
     
     
         8 . The apparatus of  claim 7  comprising:
 means for providing a retarding field to block ionized particles from travelling to the target substrate surface. 
 
     
     
         9 . The apparatus of  claim 7  comprising:
 an electrostatic deflector to remove ionized particles from the path to the target substrate surface. 
 
     
     
         10 . Apparatus for processing a substrate target surface for one or more of etching, smoothing, planarization or other modification of the substrate target surface, comprising:
 (a) means for forming gas cluster ions by a primary ionization means in a reduced pressure ambient in a chamber,   (b) means for accelerating the gas cluster ions to form an accelerated gas cluster ion beam (GCIB) along a beam path within the chamber,   (c) means for promoting fragmentation and/or disassociation of at least a portion of the gas clusters along the beam path to provide a first beam portion of energetic neutral monomers and a second beam portion of charged particles,   (d) removing the charged particle second beam portion from the beam path to form an accelerated neutral beam and allowing the accelerated neutral beam to travel toward the substrate target surface to be processed, and   (e) an assembly for implementing a step of ionizing contaminant particles in the accelerated neutral beam, if any, of larger size than the monomers and/or of lower velocity than the monomers such that the contaminant particles are ionized and further for deflecting or blocking the ionized contaminant particles, if any, in the accelerated neutral beam such that no paths for the beam to the substrate target surface to be processed exist other than through the assembly.   
     
     
         11 . The apparatus of  claim 10  wherein the assembly includes a secondary electron ionization means which is operated without detrimentally influencing the primary ionization means by employing positive offset voltages and a surrounding ground screen to prevent electrons from escaping. 
     
     
         12 . The apparatus of  claim 11  wherein further comprising means in the assembly for creating a retarding field constructed and arranged to block ionized contaminant particles from travelling to the target substrate. 
     
     
         13 . The apparatus of  claim 11  wherein further comprising means in the assembly for creating an electrostatic deflection to remove ionized contaminant particles from the path to the target substrate surface.