Electron lens and the electron beam device

Abstract

There provided a device for effectively drawing a fine pattern using a permanent magnet. The device has an outer cylinder 201 composed of a cylindrical ferromagnet with a Z axis as a central axis, a cylindrical permanent magnet 202 located inside the outer cylinder and polarized along the Z axis direction, a correction coil 204 located inside the cylindrical permanent magnet with a gap from the cylindrical permanent magnet, for adjusting a magnetic field strength generated by the cylindrical permanent magnet along the Z axis direction, and a coolant passage 203 located in the gap between the cylindrical permanent magnet and the correction coil, for allowing a coolant to flow therethrough and controlling temperature changes in the cylindrical permanent magnet.

1 . An electron lens used in an electron beam device having an electron gun for emitting an electron beam in a Z axis direction, the electron lens comprising:
 an outer tube composed of a tubular ferromagnet with the Z axis as a central axis;   a tubular permanent magnet located inside the outer tube and polarized along the Z axis direction;   a correction coil located inside or outside the tubular permanent magnet with a gap from the tubular permanent magnet, for adjusting a magnetic field strength generated by the tubular permanent magnet along the Z axis direction; and   a coolant passage located in the gap between the tubular permanent magnet and the correction coil, for allowing a coolant to flow therethrough and controlling temperature changes in the tubular permanent magnet.   
     
     
         2 . The electron lens according to  claim 1 , wherein
 a ferromagnetic ring which is thinner in the z axis direction and homogenizes a magnetic field generated by the tubular permanent magnet is located on an end surface of an electron beam emission side of the tubular permanent magnet along the Z axis direction.   
     
     
         3 . The electron lens according to  claim 1 , wherein:
 the tubular permanent magnet includes a first tubular permanent magnet located on an electron beam incoming side and a second tubular permanent magnet located on the electron beam emission side, both tubular permanent magnets being aligned along the Z axis direction;   the first tubular permanent magnet and the second tubular permanent magnet are polarized so as to generate magnetic fields in opposite directions;   the first tubular permanent magnet has a larger inner diameter than the second tubular permanent magnet; and   a central magnetic field generated by the second tubular permanent magnet is overlapped with a central magnetic field generated by the first tubular permanent magnet.   
     
     
         4 . The electron lens according to  claim 1 , further comprising another tubular permanent magnet located on the electron beam incoming side of the tubular permanent magnet, wherein
 the another tubular permanent magnet is polarized along a radial direction so that a magnetic field generated on the tubular permanent magnet side is a magnetic field which strengthens the magnetic field generated by the tubular permanent magnet.   
     
     
         5 . The electron lens according to  claim 1 , wherein the coolant passage has a tubular passage located in the gap. 
     
     
         6 . An electron beam device having a plurality of electron lens according to  claim 1  arranged on a plane generally orthogonal to a Z axis, and emitting a plurality of electron beams to a sample. 
     
     
         7 . An electron lens used in an electron beam device having an electron gun for emitting an electron beam in a Z axis direction, the electron lens comprising:
 an outer tube composed of a tubular ferromagnet with a Z axis as a central axis;   a tubular permanent magnet located inside the outer tube, polarized along a radial direction, and having a length smaller than or equal to approximately half of the outer tube along the Z axis direction; and   an inner tube composed of a tubular ferromagnet, located inside the tubular permanent magnet and having a length greater than or equal to that of the tubular permanent magnet along the Z direction.   
     
     
         8 . The electron lens according to  claim 7 , wherein
 the lens has a tubular space therein where no magnetic material is included, and a radius of the tubular space is greater than approximately one-third of a radius of an outer circumference of the outer tube.   
     
     
         9 . The electron lens according to  claim 8 , further comprising, inside the outer tube, a pair of magnet coils located so as to sandwich the tubular permanent magnet polarized along the radial direction, each coil having an inner diameter approximately equal to the inner diameter of the tubular permanent magnet, wherein
 the pair of magnet coils generate opposite magnetic fields for correcting the strength of the tubular permanent magnet.   
     
     
         10 . The electron lens according to  claim 9 , further comprising, on one or both of an upper surface and a lower surface along the z axis direction of the outer tube, a circular plate-shaped ferromagnet having a circular aperture which is greater than one-third of the radius of the outer circumference of the outer tube. 
     
     
         11 . An electron beam device having a plurality of electron lens according to  claim 7  arranged on a plane generally orthogonal to a Z axis, and emitting a plurality of electron beams to a sample. 
     
     
         12 . The electron beam according to  claim 11 , wherein:
 groups of electron lenses are aligned along an X axis direction and a Y axis direction which are generally orthogonal to the Z axis direction such that a plurality of lenses are arranged at regular intervals with a pitch PX along the X axis direction, while a plurality of lenses are arranged at regular intervals with pitch PY along the Y axis direction; and   a temperature is controlled by causing a liquid or gas coolant to flow toward the groups of electron lens.