| 摘要 |
To provide a method using compact, simple, lightweight apparatus, for canceling the effects, on a charged particle beam optical system, of magnetic fields external to the system, and of fields formed on the outer skin of a beam tube of the particle beam exposure system. External magnetic fields penetrate through the openings A, B, and C to the optical axis of the charged particle beam exposure system, disrupting the operation of the charged particle beam optical system. In this mode of the invention, as shown in the drawing, the coils 5, 6, and 7 are wound horizontally, on the illumination optical system beam tube 1 and the exposure optical system beam tube 2. Currents flowing in these coils can therefore create magnetic fields parallel to the optical axis such as to cancel external magnetic fields in that direction.. Each of the three coils (5, 6, and 7) in FIG. 3 are driven by separate power supplies capable of adjusting the individual coil currents as required to minimize the effects of flux leakage on the beam.
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