Particle-Optical Component

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 . An objective lens arrangement comprising:
 a first pole piece, a second pole piece, and a third pole piece, wherein the first, second and third pole pieces are substantially rotationally symmetric with respect to an axis of symmetry, wherein the first, second and third pole pieces are disposed on a same side of an object plane of the objective lens arrangement, 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, and wherein a radial inner end of the third pole piece is disposed at a distance from the radial inner end of the second pole piece to form a second gap;   a first excitation coil for generating a focusing magnetic field in the first gap;   a second excitation coil for generating a compensating magnetic field in the second gap;   a first power supply for supplying an excitation current to the first excitation coil; and   a second power supply for supplying an excitation current to the second excitation coil;   wherein the first and second power supplies are configured to generate the excitation currents such that a magnetic flux generated by the first excitation coil in the second pole piece is oriented in a same direction as a magnetic flux generated by the second excitation coil in the second pole piece.   
     
     
         2 . The objective lens arrangement according to  claim 1 , wherein the first power supply is configured to generate the excitation currents such that a magnetic field in a region on the object plane and about the axis of symmetry is substantially zero. 
     
     
         3 . The objective lens arrangement according to  claim 1 , further comprising:
 a fourth pole piece which is substantially rotationally symmetric with respect to the axis of symmetry, wherein a third gap is formed between the fourth pole piece and the first pole piece, and wherein the third gap is disposed at a greater distance from the object plane than the first gap; and   a third excitation coil for generating an adjusting magnetic field in the third gap.   
     
     
         4 . The objective lens arrangement according to  claim 1 , wherein the second and third pole pieces are electrically connected with each other and wherein the first pole piece is electrically insulated from the second and third pole pieces by an insulating layer. 
     
     
         5 . The objective lens arrangement according to  claim 4 , wherein the insulating layer is provided between an outer cylindrical portion integrally formed with the first pole piece and a yoke formed by the second and third pole pieces. 
     
     
         6 . The objective lens arrangement according to  claim 4 , wherein the insulating layer is provided between an outer annular disc shaped portion integrally formed with the first pole piece, and an outer portion of the second pole piece. 
     
     
         7 . The objective lens arrangement according to  claim 4 , wherein the first pole piece comprises an inner member and an outer member with the inner and outer members being electrically insulated from one another by an insulating layer. 
     
     
         8 . The objective lens arrangement according to  claim 7 , wherein the insulating layer is provided between the outer member of the first pole piece and an outer portion of the second pole piece. 
     
     
         9 . The objective lens arrangement according to  claim 7 , wherein the outer member of the first pole piece is configured to accommodate the first excitation coil and wherein the inner member of the first pole piece comprises a substantially conical portion extending towards the axis of symmetry. 
     
     
         10 . The objective lens arrangement according to  claim 7 , wherein the outer member has a substantially annular shape. 
     
     
         11 . The objective lens arrangement according to  claim 1  wherein the first gap is a substantially axial gap and the second gap is a substantially radial gap. 
     
     
         12 . The objective lens arrangement according to  claim 11 , wherein the radial inner end of the third pole piece and the radial inner end of the second pole piece are disposed in substantially a same plane extending substantially parallel to the object plane. 
     
     
         13 . The objective lens arrangement according to  claim 11 , wherein the radial inner end of the third pole piece and the radial inner end of the second pole piece are disposed closer to the object plane than the radial inner end of the first pole piece. 
     
     
         14 . The objective lens arrangement according to  claim 1 , further comprising a heating system disposed within at least one of the first and second excitation coil, the heating system comprising a heating coils disposed in the vicinity of the at least one of the first and second excitation coils and a control portion for controlling and adjusting a current passing through the heating coil. 
     
     
         15 . The objective lens arrangement according to  claim 14 , wherein the control portion is configured to adjust the current passing through the heating coil in dependence of at least one of a current passing through the at least one of the first and second excitation coils, a temperature of the third pole piece and a temperature of the second pole piece. 
     
     
         16 . An objective lens arrangement, comprising:
 an object mount for mounting an object to be processed in an object plane, the object mount having an electrical connector for supplying an electrical voltage to the object;   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 there between, wherein the second pole piece is closer to the object mount than the first pole piece, and wherein the first and second pole pieces are electrically insulated from each other;   a first excitation coil for generating a focusing magnetic field in 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 such that the beam tube is at least about 15 kV, in particular at least about 30 kV, and in particular at least about 45 kV, above ground potential;   a second voltage source for supplying a voltage to the electrical connector such that the electrical connector is grounded or at least 0.1 kV, in particular at least about 15 kV, in particular at least about 30 kV, and in particular at least about 45 kV below ground potential.   
     
     
         17 . The objective lens arrangement according to  claim 16 , further comprising a third voltage source for supplying a voltage to the second pole piece such that a potential of the second pole piece is from about 0.1 kV to about 10 kV above a potential of the electrical connector. 
     
     
         18 . An objective lens arrangement according to  claim 17 , wherein the third voltage source is an adjustable voltage source. 
     
     
         19 . An objective lens arrangement according to  claim 16 , wherein the beam tube is electrically insulated from the first pole piece. 
     
     
         20 . The objective lens arrangement according to  claim 19 , wherein the first pole piece is set substantially at ground potential. 
     
     
         21 . The objective lens arrangement according to  claim 17 , wherein the third voltage source is connected to the electrical connector and the second pole piece. 
     
     
         22 . The objective lens arrangement according to  claim 17 , further comprising a third pole piece having a radial inner end which is disposed at a distance from the radial inner end of the second pole piece to form a second gap, wherein the first pole piece is electrically insulated from the second and third pole pieces by an insulating layer. 
     
     
         23 . The objective lens arrangement according to  claim 22 , wherein the insulating layer is provided between an outer portion of the first pole piece and an outer portion of the second pole piece. 
     
     
         24 . The objective lens arrangement according to  claim 23 , wherein the first pole piece comprises an inner member and an outer member, the outer member comprising the outer portion, with the inner and outer members being electrically insulated from each other by an insulating layer. 
     
     
         25 . The objective lens arrangement according to  claim 24 , wherein the outer member of the first pole piece is configured to accommodate the first excitation coil and wherein the inner member of the first pole piece comprises a substantially conical portion extending towards the axis of symmetry. 
     
     
         26 . The objective lens arrangement according to  claim 24 , wherein the inner member of the first pole piece is disposed adjacent to the beam tube and electrically connected thereto. 
     
     
         27 . An objective lens arrangement, comprising:
 a second pole piece and a third pole piece, wherein the second and third pole pieces are substantially rotationally symmetric with respect to an axis of symmetry, wherein the second and third pole pieces are disposed on a same side of an object plane of the objective lens arrangement, wherein a radial inner end of the third pole piece is disposed at a distance from a radial inner end of the second pole piece to form a second gap, wherein the second and third pole pieces are electrically connected with each other;   a second excitation coil for generating a magnetic field in the second gap; and   a second power supply for supplying an excitation current to the second excitation coil wherein the second power supply is substantially at ground potential, a third voltage source for supplying a voltage to the second pole piece such that the second pole piece is at a potential differing from a potential of the second excitation coil by more than about 15 kV, in particular more than 20 kV, in particular more than 25 kV, and in particular more than 30 kV.   
     
     
         28 . The objective lens arrangement according to  claim 27 , further comprising:
 a first pole piece, wherein the first pole piece is substantially rotationally symmetric with respect to the axis of symmetry, wherein the first pole piece is disposed on the same side of the object plane of the objective lens arrangement as the second and third pole pieces, wherein a radial inner end of the first pole piece is disposed at a distance from the radial inner end of the second pole piece to form a first gap, and wherein the first pole piece is electrically insulated from the second and third pole pieces,   wherein the third voltage source is further configured to supply the voltage to the second pole piece such that the second pole piece is at a potential differing from a potential of the first pole piece by more than about 15 kV, in particular more than 20 kV, in particular more than 25 kV, and in particular more than 30 kV; and   a first excitation coil for generating a magnetic field in the first gap.   
     
     
         29 . The objective lens arrangement according to  claim 27 , further comprising a cooling system having a cooling medium supply for supplying a cooling medium to the second excitation coil, wherein the cooling medium supply is substantially at ground potential. 
     
     
         30 . An objective lens arrangement, comprising:
 a second pole piece and a third pole piece, wherein the second and third pole pieces are substantially rotationally symmetric with respect to an axis of symmetry, wherein the second and third pole pieces are disposed on a same side of an object plane of the objective lens arrangement, wherein a radial inner end of the third pole piece is disposed at a distance from a radial inner end of the second pole piece to form a second gap, wherein the second and third pole pieces are electrically connected with each other;   a second excitation coil for generating a magnetic field in the second gap, wherein the second excitation coil comprises a plurality of windings of an insulated wire, and wherein at least one further insulating layer is provided for supporting the second excitation coil with respect to at least one of the second and third pole pieces; and   a third voltage source for supplying a voltage to the second pole piece such that the second pole piece is at a potential differing from a potential of the compensating coil by more than about 15 kV, in particular more than 20 kV, in particular more than 25 kV, in particular more than 30 kV, and in particular more than 45 kV.   
     
     
         31 . The objective lens arrangement according to  claim 30 , further comprising:
 a first pole piece, wherein the first pole piece is substantially rotationally symmetric with respect to the axis of symmetry, wherein the first pole piece is disposed on the same side of the object plane of the objective lens arrangement as the second and third pole pieces, wherein a radial inner end of the first pole piece is disposed at a distance from the radial inner end of the second pole piece to form a first gap, and wherein the first pole piece is electrically insulated from the second and third pole pieces,   wherein the third voltage source is further configured to supply the voltage to the second pole piece such that the second pole piece is at a potential differing from a potential of the first pole piece by more than about 15 kV, in particular more than 20 kV, in particular more than 25 kV, and in particular more than 30 kV; and   a first excitation coil for generating a magnetic field in the first gap.   
     
     
         32 . The objective lens arrangement according to  claim 30 , further comprising a cooling system having a cooling medium supply for supplying a cooling medium to the second excitation coil. 
     
     
         33 . An objective lens arrangement, comprising:
 an object mount for mounting an object to be processed in an object plane, the object mount having an electrical connector for supplying an electrical voltage to the object;   a third pole piece which is substantially rotationally symmetric with respect to an axis of symmetry, wherein the third pole piece extends transversely to the axis of symmetry;   a third voltage source for supplying a voltage to the third pole piece such that the third pole piece is at a potential differing from a potential of the electrical connector by about 0.1 kV to 10 kV; and   a shielding electrode electrically insulated from the third pole piece and disposed between the third pole piece and the object mount.   
     
     
         34 . The objective lens arrangement according to  claim 33 , wherein the shielding electrode is electrically connected to the electrical connector of the object mount. 
     
     
         35 . The objective lens arrangement according to  claim 33 , wherein the shielding electrode has a substantially annular shape, wherein the axis of symmetry passes through an inner aperture formed by the annular shape. 
     
     
         36 . The objective lens arrangement according to  claim 33 , wherein the third pole piece has a surface opposite to the object mount, wherein the third pole piece has a radial inner annular portion in which the surface extends substantially parallel to the object plane at a first distance therefrom, wherein the third pole piece has a radial outer annular portion in which the surface extends substantially parallel to the object plane at a second distance therefrom, wherein the second distance is greater than the first distance, wherein the shielding electrode has an inner aperture and wherein a radial outer end of the inner annular portion of the third pole piece is disposed radially within the inner aperture of the shielding electrode. 
     
     
         37 . The objective lens arrangement according to  claim 36 , wherein the radial outer annular portion is disposed at an angle of less than 30° with respect to the object plane. 
     
     
         38 . The objective lens arrangement according to  claim 36 , wherein the radial inner annular portion is disposed at an angle of less than 20° with respect to the object plane. 
     
     
         39 . The objective lens arrangement according to  claim 36 , further comprising a second pole piece, wherein a radial inner end of the third pole piece and a radial inner end of the second pole piece form a gap between them, wherein the second pole piece has an inner angular portion with a surface facing the third pole piece and wherein the third pole piece has an angular portion with a surface facing the second pole piece, wherein the surfaces of the third and second pole pieces facing each other form an angle of less than 40°, in particular less than 35° between them. 
     
     
         40 . The objective lens arrangement according to  claim 39 , wherein the gap is a substantially radial gap. 
     
     
         41 . The objective lens arrangement according to  claim 39 , wherein the second pole piece has a radial inner portion wherein the surface facing the third pole piece is disposed at an angle of from between about 3° to about 35° with respect to the surface of the inner annular portion of the third pole piece facing the second pole piece. 
     
     
         42 . An objective lens arrangement, comprising:
 an object mount for mounting an object to be processed in an object plane;   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 second pole piece is closer to the object mount than the first pole piece;   a first excitation coil for generating a focusing magnetic field in the first gap;   a beam tube extending through a bore formed by the radial inner end of the first pole piece, wherein the bore extends from a first plane where a diameter of the bore is a minimum diameter to a second plane in which a front surface portion of the first pole piece is disposed, wherein the front surface portion is the portion of the first pole piece disposed closest to the object plane, wherein a diameter of the bore at the front surface portion is a front diameter, wherein a difference between the front diameter and the minimum diameter is more than about 10 mm, and wherein a distance between the first and second plane is more than about 5 mm; and   a first voltage source for supplying a voltage to the beam tube such that the beam tube is at a potential different from a potential of the second pole piece.   
     
     
         43 . A charged particle beam system, comprising:
 a charged particle source for generating a beam of charged particles;   at least one beam shaping lens traversed by the charged particles; and   an objective lens traversed by the charged particles, wherein the objective lens has a central axis and an object plane associated therewith, wherein at each location of the object plane where charged particles are incident, an average direction of incidence may be defined as an average over all directions under which charged particles are incident at the respective location;   wherein the at least one beam shaping lens and the objective lens are configured such that the average directions of incidence within a ring shaped inner portion of the object plane surrounding the central axis are oriented away from the central axis, and that the average directions of incidence within a ring shaped outer portion of the object plane surrounding the ring shaped inner portion are oriented towards the central axis.   
     
     
         44 . The charged particle beam system according to  claim 43 , wherein the following relation is fulfilled:
   0.5<|θ i |/|θ o |<2, wherein   θ i  is a maximum average angle of the average angles of incidence at the locations within the ring shaped inner portion, and   θ o  is a maximum average angle of the average angles of incidence at the locations within the ring shaped outer portion.   
     
     
         45 . The charged particle beam system according to  claim 44 , wherein |θ o |>1 mrad. 
     
     
         46 . The charged particle beam system according to  claim 45 , wherein the location in the outer ring shaped portion where the average angle of incidence is the maximum average angle is disposed at a distance of more than 30 μm from the central axis. 
     
     
         47 . An objective lens arrangement, comprising:
 an object mount for mounting an object to be processed in an object plane, the object mount having an electrical connector for supplying an electrical voltage to the object;   a first electrode disposed at a first distance from the object plane and having an aperture of a first diameter and concentric with a central axis of the objective lens arrangement;   a second electrode disposed at a second distance from the object plane and in between the first electrode and the object plane, and having an aperture of a second diameter and concentric with the central axis;   a first voltage supply connected to the first electrode such that the first electrode is at a first potential relative to the electrical connector;   a second voltage supply connected to the second electrode such that the second electrode is at a second potential relative to the electrical connector;   wherein the first and second distances, the first and second diameters and the first and second voltages are configured such that the following relation is fulfilled:   
       
         
           
             
               
                 
                   
                     ( 
                     
                       
                         E 
                         1 
                       
                       - 
                       
                         E 
                         2 
                       
                     
                     ) 
                   
                   
                     2 
                     · 
                     
                       ( 
                       
                         
                           E 
                           1 
                         
                         + 
                         
                           E 
                           2 
                         
                       
                       ) 
                     
                   
                 
                 < 
                 0.3 
               
               , 
             
           
         
         wherein 
         E 1  is an electrical field at the object plane in a situation where the first electrode is at the first potential relative to the electrical connector and the second electrode is at a same potential as the electrical connector; 
         E 2  is an electrical field at the object plane in a situation where the first electrode is at the first potential relative to the electrical connector and the second electrode is at a same potential as the first electrode. 
       
     
     
         48 . 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.   
     
     
         49 . The particle optical inspection system according to  claim 48 , 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. 
     
     
         50 . The particle-optical inspection system according to  claim 48 , 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. 
     
     
         51 . The particle optical inspection system according to  claim 50 , 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°.