Simplified particle emitter and method of operating thereof

Abstract

An emitter assembly for emitting a charged particle beam along an optical axis is described. The emitter assembly being housed in a gun chamber and includes an emitter having an emitter tip, wherein the emitter tip is positioned at a first plane perpendicular to the optical axis and wherein the emitter is configured to be biased to a first potential, an extractor having an opening, wherein the opening is positioned at a second plane perpendicular to the optical axis and wherein the extractor is configured to be biased to a second potential, wherein the second plane has a first distance from the first plane of 2.25 mm and above.

1 . An emitter assembly for emitting a charged particle beam along an optical axis, the emitter assembly being housed in a gun chamber and comprising:
 an emitter having an emitter tip, wherein the emitter tip is positioned at a first plane perpendicular to the optical axis and wherein the emitter is configured to be biased to a first potential;   an extractor having an opening, wherein the opening is positioned at a second plane perpendicular to the optical axis and wherein the extractor is configured to be biased to a second potential,   wherein the second plane has a first distance from the first plane of 2.25 mm and above.   
     
     
         2 . The emitter assembly according to  claim 1 , further comprising:
 an extractor support supporting the extractor, wherein the extractor support is connected to the extractor and being connectable to a housing of the gun chamber.   
     
     
         3 . The emitter assembly according to  claim 2 , wherein the extractor support is an insulating extractor support configured to prevent arcing only for voltages of 10 kV and below. 
     
     
         4 . The emitter assembly according to  claim 2 , wherein the extractor support is adapted to separate the gun chamber in a first vacuum region and a second vacuum region. 
     
     
         5 . The emitter assembly according to  claim 1 , wherein the extractor has a cup-like shape. 
     
     
         6 . The emitter assembly according to  claim 5 , wherein the extractor includes a first portion with the opening, which is essentially perpendicular to the optical axis, and a second portion surrounding the optical axis and being adapted to shield the first potential applied to the emitter. 
     
     
         7 . The emitter assembly according to  claim 1 , wherein the emitter or the extractor is movable such that the first distance can be varied. 
     
     
         8 . The emitter assembly according to  claim 1 , further comprising:
 a suppressor configured to be biased to a suppressor potential, wherein the suppressor potential can be varied.   
     
     
         9 . A gun chamber for a charged particle beam device, comprising:
 an emitter assembly, the emitter being housed in the gun chamber and comprising:
 an emitter having an emitter tip, wherein the emitter tip is positioned at a first plane perpendicular to the optical axis and wherein the emitter is configured to be biased to a first potential; 
 an extractor having an opening, wherein the opening is positioned at a second plane perpendicular to the optical axis and wherein the extractor is configured to be biased to a second potential, 
 wherein the second plane has a first distance from the first plane of 2.25 mm and above; and 
   the gun chamber further comprises:   an electrode having an opening for trespassing of the charged particle beam and being configured to be biased to a third potential;   
     
     
         10 . The gun chamber according to  claim 9 , comprising:
 a housing of the gun chamber having at least one vacuum connection adapted for connecting a vacuum pump, wherein the extractor support is connected to the extractor and the housing of the gun chamber.   
     
     
         11 . The gun chamber according to  claim 10 , further comprising:
 a second vacuum connection adapted for connecting a vacuum pump, wherein the vacuum connection is positioned to evacuate the first vacuum region and the further vacuum connection is positioned to evacuate the second vacuum region.   
     
     
         12 . The gun chamber according to  claim 9 , wherein the electrode is positioned at a second plane perpendicular to the optical axis and wherein the distance between the third plane and the second plane is smaller than 1.5 times the first distance. 
     
     
         13 . The emitter assembly according to  claim 1 , wherein at least two of the emitter assemblies are combined to form a charged particle beam device. 
     
     
         14 . The emitter assembly according to  claim 13 , wherein each of the emitters of the at least two emitter assemblies is connected to one power supply for providing the first potential to the emitters. 
     
     
         15 . The emitter assembly according to  claim 13 , wherein the at least two emitter assemblies are provided within a gun chamber, wherein the gun chamber further comprises an electrode having an opening for trespassing of the charged particle beam and being configured to be biased to a third potential. 
     
     
         16 . A method of operating the emitter assembly according to  claim 10 , wherein the voltage between the first potential and the second potential is at least 20 kV. 
     
     
         17 . The method according to  claim 16 , further comprising:
 biasing an electrode having an opening for trespassing of the charged particle beam to a third potential, wherein the voltage between the second potential and the third potential is 15 kV or below, particularly 10 kV or below.   
     
     
         18 . The method according to  claim 17 , wherein the voltage between the second potential and the third potential is 10 kV or below. 
     
     
         19 . The method according to  claim 16 , wherein the first potential is shielded by a portion of the extractor surrounding the optical axis.