Worker exposures during maintenance of ion implanters in the semiconductor industry

An industrial hygiene survey of two semiconductor plants was performed in order to characterize and quantify toxic emissions during preventive maintenance of standard ion implantation machinery used in the semiconductor industry. Maintenance personnel at both plants were monitored during routine preventive maintenance procedures. Plant B was evaluated during two separate ion implanter maintenance operations, while monitoring at plant A. was performed only once. The maintenance procedures differed for each sampling visit. A comparison is presented between grinding operations, bead blasting and use of Scotch Brite scouring pads and solvents. Personal breathing zone air samples were collected for the determination of arsenic, arsine, phosphine, and many constituent elements found during the dismantling operations. Personal samples were collected for the determination of the following cleaning solvent vapors which were during parts cleaning: methyl chloroform, acetone, isopropanal, and Freon 113. Wipe samples were obtained at plant B to determine the presence of any toxic substances, the potential for skin absorption or ingestion, and to define the extent of contaminated areas along with effectiveness of decontamination procedures. Area samples were obtained to determine the concentration of airborne contaminants at a fixed location within both plants. These samples provide information about engineering controls, sources of air contaminants, and the potential for employee exposure. The results of all the air sampling were compared to the threshold limit values and permissible exposure levels for these substances. Most of the air samples indicated low time-weighted averaged concentrations of the sampled contaminants. However, high arsenic exposures were seen during maintenance grinding operations. Arsine was generated during the grinding operation and in the course of bead blasting. Very low concentrations of the solvent vapors were detected during any of the cleaning operations. The potential for significant overexposure to hazardous substances during maintenance of ion implanters does exist, especially if grinding if preformed. These exposures can be minimized with the proper utilization systems, respiratory protection and adjustment of work practices.