Characteristics of Peak Exposure of Semiconductor Workers to Extremely Low-Frequency Magnetic Fields.

Objectives: Peak exposure to extremely low-frequency magnetic fields (ELF-MF) among semiconductor workers was characterized by type of factory, operation, and job.

Methods: A portable EMDEX meter was used to monitor the ELF-MF exposure of 117 semiconductor workers who are involved in wafer fabrication (fab) and assembly operations. ELF-MF measurements were logged every 3 s and categorized by process and job or activity during working hours. Two values of 0.5 and 1 μT were adopted subjectively as cutoff values of peak exposure levels based on a literature review.

Results: All semiconductor workers who were involved in diffusion, ion implanter operation, module, and chip test were exposed to ELF-MF higher than 0.5 μT during their entire working time. Engineers who maintained electric facilities in the semiconductor operations were exposed to the highest ELF-MF peak levels (2.5 μT on average above 0.5 μT and 3.6 μT on average above 1 μT). Operators working in chip testing showed the highest daily contribution of their peak levels to their daily average ELF-MF exposure levels (98.1% and 83.9%). In contrast, chemical mechanical planarization engineers, wafer test operators, and administrative workers outside clean rooms showed average exposure to less than 0.5 μT and a low proportion of duration of time exposed above either the 0.5 μT or 1 μT peak level points, along with a low daily contribution of peak exposure levels (16.0, 11.9, and 18.7%).

Conclusions: Most of the activities and working locations next to machines generating ELF-MF in semiconductor operations showed high contributions of ELF-MF peak exposure to daily exposure dose despite their relative minor fraction of workers' daily time.