Tubular permanent magnet used in a multi-electron beam device

An electron beam device having a plurality of electron lenses arranged on a plane generally orthogonal to a Z axis, and emitting a plurality of electron beams to a sample, the electron beams emitted in the Z axis direction from electron guns, wherein each electron lens comprises:

• 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, the electron beam passing through;
• the tubular permanent magnet generating a magnetic field greater than 4000 Gauss immediately above the surface of the sample and focusing the electron beam to the surface of the sample;
• a ferromagnetic ring which is thinner than the tubular permanent magnet in the z axis direction and homogenizes the magnetic field generated by the tubular permanent magnet is located between the tubular permanent magnet and the sample, on an end surface of an electron beam emission side of the tubular permanent magnet along the Z axis direction with an outer diameter of the ferromagnetic ring being smaller than the outer diameter of the tubular permanent magnet and the inner diameter of the ferromagnetic ring is the same as the inner diameter of the tubular permanent magnet;
• and
• the electron lens is a final lens for the electron beam that is emitted to the sample.