Multi-column electron beam exposure apparatus and magnetic field generation device

A multi-column electron beam exposure apparatus comprising:

• a plurality of column cells;
• an electron beam converging unit in which two annular permanent magnets and an electromagnetic coil are surrounded by a ferromagnetic frame, each of the two annular permanent magnets being magnetized in a direction of an optical axis and being symmetrical about the optical axis, the electromagnetic coil being disposed near the annular permanent magnets and used to adjust a magnetic field of the annular permanent magnets;
• a substrate provided with circular apertures through which electron beams used in the column cells pass, respectively, the substrate having the electron beam converging unit disposed in a side portion of each of the circular apertures;
• two annular permanent magnets are disposed one above the other in the direction of the optical axis with the electromagnetic coil directly interposed therebetween, and polarities of the annular permanent magnets are oriented in a same direction;
• and
• wherein strength of the magnetic field of the annular permanent magnets is within a range from 5% lower to 5% higher than required magnetic field strength.