In-chamber electron detector

Abstract

A secondary particle detector 302 for a charged particle beam system 300 includes a scintillator 304 and a transducer 312, such as a photomultiplier tube, positioned within a vacuum chamber 107 . Unlike prior art Everhart-Thornley detectors, the photomultiplier is positioned within the vacuum chamber, which improves detection by eliminating optical couplings and provides flexibility in positioning the detector.

1 . A charged particle beam system, comprising:
 a source of charged particles;   a focusing column for forming a charged particle beam from the charged particles emitted by the charged particle beam source;   a sample vacuum chamber containing a sample stage for holding a sample to which the charged;   a secondary particle detector positioned within the vacuum chamber, the detector including:
 a scintillator for emitting light when impacted by a secondary electron, and 
 a transducer for detecting the light emitted by the scintillator and converting the light to an electric current; 
   characterized in that the scintillator and transducer are all positioned within the sample vacuum chamber.   
     
     
         2 . The charged particle beam system of  claim 1  in which the transducer comprises a photomultiplier tube, a photodiode or a phototransistor. 
     
     
         3 . The charged particle beam system of  claim 1  further comprising a second source of charged particles and a second focusing column for forming a charged particle beam from the charged particles emitted by the second charged particle beam source. 
     
     
         4 . The charged particle beam system of  claim 1  in which the position of the secondary particle detector is adjustable within the vacuum chamber to improve the collection of secondary particles. 
     
     
         5 . The charged particle beam system of  claim 1  in which the secondary particle detector includes an ion-to-electron converter. 
     
     
         6 . The charged particle beam of  claim 1  further comprising a light tube to conduct light from the scintillator to the transducer. 
     
     
         7 . The charged particle beam system of  claim 6  in which the light tube is less than 25 mm long. 
     
     
         8 . The charged particle beam system of  claim 6  in which the light tube is less than 15 mm long. 
     
     
         9 . The charged particle beam system of  claim 1  in which the secondary particle detector is less than 120 mm long. 
     
     
         10 . The charged particle beam system of  claim 9  in which the secondary particle detector is less than 60 mm long. 
     
     
         11 . The charged particle beam system of  claim 1  further comprising a conductive grid before the scintillator, the grid attracting charged particles toward the detector. 
     
     
         12 . The charged particle beam system of  claim 1  further comprising an ion-to-electron converter positioned before the scintillator. 
     
     
         13 . The charged particle beam system of  claim 12  in which the ion-to-electron converter includes a cylindrical surface for converting secondary ions to electrons. 
     
     
         14 . A method of detecting secondary electrons, comprising:
 directing a primary charged particle beam toward a sample surface in a sample vacuum chamber;   attracting charged particles emitted from the surface upon impact of the primary charged particle beam toward a material within the vacuum chamber that emits photons upon the impact of a charged particle;   detecting the photons and converting the photons to an electric current using a transducer, the current being proportional to the number of charged particles detected from the sample surface upon impact of the charged particle beam; and   conducting the electric current from the vacuum chamber, characterized in that the photons are converted to an electric current within the vacuum chamber.   
     
     
         15 . The method of  claim 14  in which directing a primary charged particle beam toward a sample surface in sample vacuum chamber includes directing an ion beam or an electron beam. 
     
     
         16 . The method of  claim 14  in which the transducer is a photomultiplier tube, a photodiode or a phototransistor. 
     
     
         17 . The method of any of  claims 14  further comprising conducting photons through a light tube toward the transducer. 
     
     
         18 . The method of any of  claims 14  in which detecting and converting the photons to an electric current within the vacuum chamber includes detecting and converting the photons to an electric current within a device that is less than 15 cm long. 
     
     
         19 . The method of any of  claims 14  in which attracting charged particles emitted from the surface upon impact of the primary charged particle beam further includes attracting ions and further comprising converting the ions to electrons. 
     
     
         20 . A secondary particle detector sufficiently compact for being positioned within the vacuum chamber of a scanning, the detector comprising:
 a scintillator for emitting light when impacted by a secondary electron;   a transducer for detecting the light emitted by the scintillator and converting the light to an electric current;   a light guide for guiding light from the scintillator to a transducer, the light guide providing a light path from the scintillator to the transducer that is shorter than 50 mm.   
     
     
         21 . (canceled) 
     
     
         22 . (canceled) 
     
     
         23 . (canceled)