Charged particle beam device for inspection of a specimen with a plurality of charged particle beamlets

Abstract

The invention relates to a charged particle beam device for inspection of a specimen with a plurality of charged particle beamlets. The charged particle beam device comprises a specimen holder for holding a specimen; a source for producing a beam of charged particles; and an illuminator for converting said beam of charged particles into a plurality of charged particle beamlets and directing said plurality of charged particle beamlets onto said specimen. According to the disclosure, the illuminator comprises a multi-aperture lens plate having a plurality of apertures for defining the corresponding plurality of charged particle beamlets; as well as at least a first electrode for generating an electrical field at a surface of the multi-aperture lens plate. The apertures in said multi-aperture lens plate have a noncircular cross-sectional shape to correct for neighbouring aperture induced aberrations. This allows for decreased spot size, and with this imaging resolution of the device is increased.

1 . A charged particle beam device for inspection of a specimen with a plurality of charged particle beamlets, the charged particle beam device comprising:
 a specimen holder for holding a specimen;   a source for producing a beam of charged particles;   an illuminator for converting said beam of charged particles into a plurality of charged particle beamlets and directing said plurality of charged particle beamlets onto said specimen, wherein said illuminator comprises:
 a multi-aperture lens plate having a plurality of apertures for defining the corresponding plurality of charged particle beamlets, wherein said apertures have a noncircular cross-sectional shape; and 
 a first electrode for generating an electrical field at a surface of the multi-aperture lens plate; and 
   a detector for detecting a flux of radiation emanating from the specimen in response to said irradiation by said plurality of charged particle beamlets.   
     
     
         2 . The charged particle beam device according to  claim 1 , wherein said apertures are identical. 
     
     
         3 . The charged particle beam device according to  claim 1 , wherein the apertures have a continuously curved perimeter. 
     
     
         4 . The charged particle beam device according to  claim 1 , wherein the cross-sectional shape has a first axis as measured in a first direction, and a second axis as measured in a second direction substantially orthogonal to the first direction, wherein the second axis is larger than the first diameter. 
     
     
         5 . The charged particle beam device according to  claim 1 , wherein the cross-sectional shape has at least two axes of symmetry. 
     
     
         6 . The charged particle beam device according to  claim 1 , wherein the cross-sectional shape has at least four axes of symmetry. 
     
     
         7 . The charged particle beam device according to  claim 1 , wherein the apertures have an oval, ellipsoid, rounded square or rounded rectangular cross-sectional shape. 
     
     
         8 . The charged particle beam device according to  claim 1 , wherein the aperture plate additionally comprises at least one beamlet shape tuning element provided in between adjacent apertures and arranged for locally modifying said electrical field at said surface of the multi-aperture lens plate. 
     
     
         9 . The charged particle beam device according to  claim 8 , wherein said beamlet shape tuning element comprises a recess in said multi-aperture lens plate. 
     
     
         10 . The charged particle beam device according to  claim 9 , wherein said recess is a blind hole. 
     
     
         11 . The charged particle beam device according to  claim 8 , wherein said beamlet shape tuning element comprises a protrusion on said multi-aperture lens plate. 
     
     
         12 . The charged particle beam device according to  claim 8 , wherein said beamlet shape tuning element is provided substantially halfway in between said adjacent apertures. 
     
     
         13 . The charged particle beam device according to  claim 8 , wherein a diameter of said beamlet shape tuning element is in between 0.25 to 0.75 of a diameter of said apertures, and in particular equal to 0.5. 
     
     
         14 . A multi-aperture lens plate in a multi-beam charged particle beam device, comprising: a plurality of apertures for defining a plurality of charged particle beamlets, wherein each of the plurality of apertures has a noncircular cross-sectional shape. 
     
     
         15 . The multi-aperture lens plate according to  claim 14 , wherein a perimeter of each of the apertures does not have a sharp edge. 
     
     
         16 . The multiple-aperture lens plate according to  claim 14 , wherein the apertures have a continuously curved perimeter. 
     
     
         17 . The multi-aperture lens plate according to  claim 14 , wherein said apertures are identical in shape. 
     
     
         18 . The multi-aperture lens plate according to  claim 14 , wherein said apertures are identical in orientation. 
     
     
         19 . The multi-aperture lens plate according to  claim 14 , wherein the apertures have an oval, ellipsoid, rounded square or rounded rectangular cross-sectional shape. 
     
     
         20 . The multi-aperture lens plate according to  claim 14 , further comprising at least one beamlet shape tuning element provided in between adjacent apertures.