In-depth survey report: control technology for gallium arsenide processing at M/A-COM, Lowell, Massachusetts, report no. CT-163-13b.
Control technology for gallium-arsenide (GaAs) processing was investigated at M/A-COM (SIC-3674), in Lowell, Massachusetts. GaAs wafers, field effect transistors, and monolithic microwave integrated circuits were produced by M/A-COM. Personal and area samples for arsenic (7440382) and gallium (7440553) were collected on 37 millimeter diameter cellulose ester, 0.8 micrometer pore size filters. Principles of control involve engineering measures, work practices, personal protection, and monitoring. Arsenic wipe samples were collected on various surfaces in specified areas of possible heavy contamination. Arsenic exposure was well controlled at this site with personal exposures falling well below the NIOSH standard of 2 micrograms/cubic meter. Area concentrations of arsenic were higher near the saws than at the grinders and edge bevelers. Arsenic concentrations were ten times higher on Thursday, the fourth day of the study, as compared to Monday when the study began, partly because two saws were operated on Thursday, whereas only one was in operation on Monday. The authors recommend that exposure of the Liquid Encapsulated Czochralski (LEC) cleaning operator to arsenic be reduced by controlling emission sources during cleaning. It also appeared that the local exhaust ventilation at the LEC wet bench may be inadequate for the control of acid emissions during certain operations such as acid removal of the frozen GaAs ingots.