Alignment of low-energy electron beams using magnetic fields

摘要

For wafer or mask fabrication using electron beam scanning lithography, a registration mark which is a small magnetic field generator is located on the surface of the substrate which is being subject to processing. The magnetic field generator, which is typically a small area of ferromagnetic particles which are magnetically aligned, forms a magnetic field which penetrates through any overlying resist or oxide layer. The magnetic field of the registration mark is strong enough to alter the trajectory of secondary electrons produced by the incident low-energy electron beam. A suitably configured detector detects this alteration in the secondary electron beam caused by local presence of the magnetic fields. An example of a suitable registration mark is a small rectangular area of ferromagnetic particles.