Objective lens arrangement usable in particle-optical systems

Abstract

An objective lens arrangement includes a first, second and third pole pieces, each being substantially rotationally symmetric. The first, second and third pole pieces are disposed on a same side of an object plane. An end of the first pole piece is separated from an end of the second pole piece to form a first gap, and an end of the third pole piece is separated from an end of the second pole piece to form a second gap. A first excitation coil generates a focusing magnetic field in the first gap, and a second excitation coil generates a compensating magnetic field in the second gap. First and second power supplies supply current to the first and second excitation coils, respectively. A magnetic flux generated in the second pole piece is oriented in a same direction as a magnetic flux generated in the second pole piece.

1 - 51 . (canceled) 
     
     
         52 . A particle optical inspection system, comprising an objective lens arrangement comprising:
 a first pole piece and a second pole piece, wherein the first and second pole pieces are substantially rotationally symmetric with respect to an axis of symmetry, wherein a radial inner end of the first pole piece is disposed at a distance from a radial inner end of the second pole piece to form a first gap, wherein the first pole piece has an inner portion extending at an angle towards the axis of symmetry and wherein the first and second pole pieces are electrically insulated from each other;   an first excitation coil for generating a focusing magnetic field in a region of the first gap;   a beam tube extending through a bore formed by the radial inner end of the first pole piece;   a first voltage source for supplying a voltage to the beam tube;   the particle-optical inspection system further comprising a beam path splitting arrangement comprising at least one magnetic field arrangement, wherein a lower end of the at least one magnetic field arrangement of the beam path splitting arrangement is disposed at a first distance from the object plane and wherein an upper end of the first excitation coil is disposed at a second distance from the object plane and wherein the first distance is shorter than the second distance.   
     
     
         53 . The particle optical inspection system according to  claim 52 , wherein the inner portion of the first pole piece extends towards the axis of symmetry such that the radial inner end of the first pole piece is disposed closer to the object plane than a radial outer end of the inner portion of the first pole piece and wherein the lower end of the at least one magnetic lens is disposed within a space defined by the inner portion of the first pole piece. 
     
     
         54 . The particle-optical inspection system according to  claim 52 , wherein the inner portion of the first pole piece has a substantially conical shape with the radial inner end being disposed closer to the object plane than a radial outer end and wherein the lower end of the at least one magnetic lens is disposed within the conus formed by the inner portion of the first pole piece. 
     
     
         55 . The particle optical inspection system according to  claim 54 , the conus formed by the inner portion of the first pole piece having a conus opening angle in a range of from about 20° to about 70°.