Effects of Lighting Environment on Visual Sensitivity, Cognition Memory Performance, Fatigue and Comfort in Lithography Area

In the past decades, the semiconductor and the light emitting diode (LED) industries grew rapidly in Taiwan and the number of fab with lithography area kept increasing. Thus, workers exposed to yellow light at work increased as well. In order to protect photo resistor, light of wavelength less than 500 nm would be blocked using yellow fluorescent lightening, which might modify workers’ perception of color as well as visual performance. This study aimed to characterize on-site lighting environment in both lithography area and its adjacent area, and assess the workers’ exposure to the particular lighting at work in a wafer fab. To clarify the possible association between lighting environment and visual performance of workers, this study was carried out in the lithography area and its adjacent area of a LED fab for comparison. There were 24 workers recruited in this study, half of them working in lithography area (exposed group), and the others working in the adjacent area (control group). Spectrometer was applied to measure the lighting condition in both areas. Visual sensitivity test, cognition memory performance test, fatigue and comfort assessment were applied to assess the workers’ visual performance. Results of lighting measurement at work places demonstrated that not only light with wavelength less than 500 nm were blocked in lithography area, but also the illumination (292 lux) and correlated color temperature (2223 K) in this working area were much lower as compared to its adjacent area. Moreover, all the visual tests’ results showed poorer visual performance for workers in lithography area as compared to those workers in the adjacent area. The error scores of color perception test were 91.5 points and 26.8 points for exposed group and control group, respectively (p<0.0001). Besides, the workers in lithography area were prone to get visual fatigue and feel uncomfortable under yellow lighting. Results of this study suggested that the illumination of lithography area might need to be increased and the workers in lithography area might need to be routinely rotated in order to prevent adverse effect on visual performance. However, difference in visual performance between study groups was hard to be attributed to any lighting related parameter since none of them could be manipulated in this field study for research purpose. In future, a long-term follow-up study with larger sample size is warranted to clarify possible adverse effects resulting from working in lithography area by controlling confounding factors. It’s expected that our findings would urge the industry to improve and practice suitable management in lithography area for working environment and condition. In addition, these findings could be used as reference for the working area rotation plan.