Passive Magnetic Shielding System in ELF

The extremely low frequency (ELF) magnetic field has significant impact on yield rate especially when the technical note reaches less than 14 nanometer in next-generation nano-Fab. For sensitive equipment such as the SEMs, TEMs, STEMs, FIB writers, and E-beam writers, it suggests that the ELF magnetic field should be lower than 0.3 milli-Gauss to guarantee good yield. Therefore, mitigating the magnetic field by active/passive approaches such as the material shielding, and active canceling are highly demanded. This study focuses on the development of a passive magnetic field shielding system which consists of two types of materials, conductor and high magnetic permeability metal alloys, combining the assembling of materials and design of shape of the shielding box. With the help of shielding material’s magnetic permeability, eddy current, reflecting and absorbing to mitigate the incoming electromagnetic field, the order of material in different order will also be considered to make the best shielding effect. Base on the experiments in this study, the prototype system is able to reduce the magnetic field intensity from 9.88mG to 0.5mG at 60Hz and reducing over 95% at 9K Hz. This thesis begins with the introduction of the regulations about EMI nowadays, the theory about passive shielding works, and the shielding material properties. After describing the simulation framework, experimental results are presented.