The resolution of an electron beam lithography system (EBLS) is affected by low frequency magnetic noise due to trains, cars, elevators, and electrical devices. Active shielding, in which magnetic noise is shielded by compensation coils, can obtain a high shielding factor at low frequencies and provide better cost performance and flexibility than magnetically shielded rooms. In this paper, four configurations for the compensation coils of an active shield were proposed (large and small two- and four-square coils). Experiments using the EBLS model and 3-D magnetic field computations were carried out to find an optimal configuration for the compensation coils and for the position of the pickup sensor outside the EBLS, where the magnetic disturbance inside the EBLS could effectively be reduced.
