Magnetically shielded enclosures and associated methods for protecting a field-sensitive system from stray external magnetic fields

摘要

Magnetically shielded enclosures (e.g., rooms) and associated methods are disclosed for containing and magnetically shielding a field-sensitive system such as a charged-particle-beam (CPB) microlithography system without having to make the enclosure excessively large. The CPB microlithography system includes a lens column and substrate chamber collectively forming an internal shielding barrier. The shielded enclosure is in external surrounding relationship to the internal shielding barrier. The shielded enclosure includes a wall that defines an aperture through which some of the stray external magnetic field can penetrate to inside the enclosure. Some of the external magnetic field also leaks through the enclosure walls. The aperture is situated and configured such that the external magnetic flux leaking through the aperture (which flux tending to be directed toward the enclosure walls) and other external magnetic flux leaking through the enclosure walls (which flux tending to be directed toward the internal shielding barrier) at least partially cancel each other. This cancellation reduces the amount of the leakage flux that penetrates the internal shielding barrier to the field-sensitive system inside the barrier.