半導體產業MOCVD機台維修工程師金屬物質暴露情形之探討

Abstract

背景：由於近年來各國政府開始禁售白熾燈泡，LED（Light Emitting Diode）漸漸取代傳統照明，自2008到2012年以來全球LED產值成長率高達100%以上。有機金屬化學氣相沉積（metal organic chemical vapor deposition, MOCVD）為製造LED的重要製程之一，但所使用的有機金屬化學物質對人體的健康效應卻仍不清楚。MOCVD機台需定期由工程師將其拆開進行維修保養（preventive maintenance），此時機台內部的製程殘餘物質可能逸散至環境中，造成維修保養工程師暴露之危害。 目的：了解維修工程師進行MOCVD機台維修保養作業時，潛在環境金屬暴露的情形；釐清機台維修過程中金屬化學物質暴露機會較高的作業內容；並評估維修工程師是否會將金屬物質帶離維修工作現場，造成二次汙染。 方法：利用直讀式儀器、沾黏採樣、擦拭採樣、空氣採樣等方法，針對某一LED廠MOCVD機台維修作業環境及不同作業單元進行採樣，並將樣本微波消化後利用感應耦合電漿質譜儀分析樣本中金屬濃度。 結果：維修保養作業當日環境中的懸浮微粒數目濃度高於非維修保養作業日約20-1600倍。沾黏採樣結果顯示維修保養作業後有相對較多金屬累積於手掌及手腕部位，樣本中最高鎵金屬含量分別為0.037及0.036 µg/cm2。重複使用的無塵衣物及防護具表面會殘留金屬，成為二次汙染源。擦拭採樣發現維修保養作業後會有大量的金屬物質留存於環境中，其樣本鎵金屬含量平均值為859.9 µg/100 cm2，最高值可達7399 µg/100 cm2。空氣採樣結果顯示，工程師在擦拭上蓋及擦拭零件等作業單元中暴露金屬的機會最高。 結論：本研究利用現場實測的數據，證實維修保養作業工程師有潛在暴露金屬物質之風險，其中鎵金屬之暴露量最高。同時應用空氣採樣、沾黏採樣、擦拭採樣等採樣方式，對此類作業時間短但環境中有高濃度金屬暴露的作業場所進行採樣，可有效協助評估吸入及皮膚暴露途徑的潛在風險。本研究期許能促使工業界及政府開始重視使用新興化學物質所衍生之問題，了解、改善作業環境之重要性，並可作為未來制定法規之參考依據。

Background: In recent years, as the sale of incandescent light bulb is prohibited in many countries, LED (Light Emitting Diode) products gradually replaced the traditional lights, and the global LED production value grew by more than 100% during 2008-2012. Metal-containing chemical substances were widely used in the LED optoelectronics industry for metal organic chemical vapor deposition (MOCVD). However, the health effects of these chemicals remain unclear. Preventive maintenance engineers working on MOCVD are potentially exposed to residues of toxic metals resulted from maintenance task through skin contact or inhalation. Objectives: To characterize potential metal exposure for engineers during their preventive maintenance on MOCVD, to clarify the tasks with relative high risk of metal exposure, and to verify if any metal residuals disseminated from working site by the preventive maintenance engineers. Materials and Methods: Direct-reading instrument, tape-strip sampling, wipe sampling, and air sampling were applied in this study to profile the metal exposure in the working environment by task during the MOCVD preventive maintenance. Collected samples were first digested with microwave and the metal concentrations were determined by inductively coupled plasma mass spectrometer. Results: The count concentration of particulates suspended in the work environment during preventive maintenance was 20-1600 times higher than non-maintenance work. Results of tape-strip samples showed that the highest amount of gallium accumulated on engineers’ palm and wrist after the preventive maintenance work, with maximum gallium of 0.037 and 0.036 µg/cm2, respectively. Besides, metal residues were detected on the surface of reused cleanroom clothing and personal protective equipment, which might cause secondary pollution. Results of wipe sample analysis showed that there were high amounts of metal residues in the environment after preventive maintenance work, and the average gallium loading on floor wipe samples was 859.9 µg/100 cm2, and the highest one was 7399 µg/100 cm2. Air samples showed the preventive engineers might be occupationally exposed to substantial metals during the MOCVD preventive maintenance, especially in the tasks of shelters cleaning and parts cleaning. Conclusions: In this study, we confirmed that the maintenance engineers might be potentially exposed to metal substances, especially for gallium. It’s demonstrated that simultaneously applying air sampling, tape-strip sampling, and wipe sampling methods would facilitate the evaluation of potential risks of metal exposure through inhalation and dermal exposure routes in this kind of workplace. It’s appropriate to use these methods in environmental monitoring for high metal concentration during a specific short-time task. It’s also expected that our findings would urge the industry and the government to pay more attention to the relevant issues resulted from the use of emerging chemicals, and to appreciate the importance of improving the working environment. In addition, these findings could also be used as references for the establishment of related regulations in the future.