作業環境臭氧的逸散問題及改善研究

Abstract

在某硬碟零件廠使用短波長紫外光(UV)作為改變碟片表面特性之技術時，會因光敏氧化作用而產生具刺激氣味之臭氧，並隨著基板入口端及出口端逸散至潔淨室，造成工作環境中的空氣污染。本研究探討及改善此作業境污染問題，並提出改善方案。 本研究的實驗在Class 10的潔淨室內進行，於燈罩下方與基板出口加入抽氣系統及UV照射設備周圍加裝抗UV光外洩的壓克力防護，並將一般壓克力延伸至接近高效率空氣慮網(HEPA，High Efficiency Particulate Air Filters)處，增加UV照射設備內的下降層流壓力，減少UV燈與大氣環境接觸，可大幅降低臭氧產生，目前已降低設備周圍的臭氧濃度，由改善前的150ppb以上，降低至約75ppb，效率50%，單一設備硬體改善成本約為3~5萬元。 為了進一步降低臭氧逸散，使用流動氮氣注入UV燈管之腔體，阻絕UV光與大氣接觸，配合第一階段的研究，使設備周圍之臭氧濃度降至5ppb以下。而此改善方案之單一設備每年耗費氮氣成本為15萬7千元，改善臭氧逸散效率為96%。

The technology of Shortwave Ultraviolet has been widely applied in industrial productions, for instance, substrate (stuff) cleaning, exposure process of semiconductor, or for the purposes of having more stable characteristics of coating in baking procedure. However, when an equipment of Shortwave Ultraviolet technology is used, it produces poisonous ozone with stinky smell at the same time because the photosensitized oxidation happens during the process. The ozone may disperse into a clean room through input or output ports of the devices resulting in air pollution in work environments. In this thesis, we will talk about the operating environment pollution of ozone which results from the instruments of high power Ultraviolet (with 185nm shortwave or other wavelengths) will be discussed and the O3 reduction methods and results will be shown.

The experiment was conducted in a Class 10 clean room. In the first stage of the improvement, after the photomask was improved, the exposure of the UV light to the ambient atmosphere was decreased resulting in a substantial reduction of the amount of ozone produced. Air-extracting systems were also installed under lampshades and at the inlet port of the substrate. Besides, Anti-UV Acrylic shields were installed around the Ultraviolet Radiation devices and extended to the position of the HEPA(High Efficiency Particulate Air Filters). The pressure of descending air flow in a UV radiation equipment was found to be increased. After that, the average ozone concentration was decreased from more than 150ppb to about 75ppb.

In the second stage of the improvement, nitrogen was injected into a cavity of UV light to prevent ozone from the UV light from releasing to environmental atmosphere. Integrating with the first stage of the work, the average ozone concentration around the equipment was further decreased to 5ppb or less.