Evaluation of Arsenic Exposure Improvement Program for the Preventative Maintenance of Ion Implanter

• Main Authors: I-Chun Lu, 呂逸群
• Other Authors: Yaw-Huei Hwang
• Format: Others
• Language: zh-TW
• Published: 2002
• Online Access: http://ndltd.ncl.edu.tw/handle/24370834611908771626

碩士 === 國立臺灣大學 === 職業醫學與工業衛生研究所 === 90 === Ion implantation is a critical process in semiconductor fabrication. Usually, the elements of group III and V(A) of the periodical table are the choice for dopants in this process. Among them, arsenic was used more frequently comparing with others. After a period of operation, the preventative maintenance would be performed for the ion implanter. During this work, the engineers have potential exposure to arsenic when they were disassembling or cleaning the parts of implanter. The study aim of the present study was to identify the exposure of arsenic and arsine at work environment and for the engineers in order to provide an arsenic exposure improvement program and evaluate its effectiveness. Both arsenic and arsine existed in the work area. The arsenic residues were always coated on source chamber or certain parts of the implanter. However, arsine did not come from the fabrication process or duct leaking but the byproduct of the chemical reaction of elemental arsenic and H2O2, which was used as oxidant in the arsenic-cleaning process. Therefore, there was a higher arsine level during the process of spraying H2O2 to finish source chamber clean-up. Furthermore, wipe samples manifested that the arsenic (As) would deposit on floors, tools and surface of cleans suits. In order to prevent the hazard of arsenic and arsine, the proposed improvement program was not only recommended but also executed in field in the present study. The practice included the use of supplied air respirator (SAR) with full facepiece, wearing Tyvek suit, and correctly conducting local ventilation and good housekeeping. Although the results of the present study showed that airborne arsenic (As) and arsine (AsH3) levels were very low and all below the permissible exposure limit (PEL) in Taiwan, i.e., 0.5 mg/m3 for arsenic, and 0.05 ppm for arsine, it does not mean that the preventative maintenance of ion implanter is absolutely safe, especially for inorganic arsenic, which has already been concerned as human carcinogen. A work environment improvement program following the principle of “Plan-Do-Check-Action” (P-D-C-A) is expected to prevent the arsenic exposure at work.