| 摘要 |
Charged-particle-beam (CPB) optical systems are disclosed in which external magnetic fields are effectively canceled. Such systems are especially suitable for use in CPB microlithography systems in which extreme isolation from external magnetic fields is required in each of the lens columns of the system. In an embodiment, four magnetic-field sensors are situated downstream of the substrate stage of the CPB microlithography system. The sensors are located in a plane perpendicular to the optical axis and situated equi-angularly relative to each other about the optical axis. Each sensor can be configured as, e.g., a Hall-effect sensor, a magnetic-resistance sensor, or a search coil (the latter for detecting AC magnetic fields). Most desirably, the sensors are incorporated into a single sensor capable of detecting magnetic fields in each of the X, Y, and Z directions. The sensors can be used in conjunction with an active-canceller.
|
