Industrial Hygiene and Control Technology Assessment of Ion Implantation Operations

Abstract

Ion implantation is a process used to create the functional units (pn junctions) of integrated circuits, photovoltaic (solar) cells and other semiconductor devices. During the process, ions of an impurity or a "dopant" material are created, accelerated and imbedded in wafers of silicon. Workers responsible for implantation equipment are believed to be at risk from exposure to both chemical (dopant compounds) and physical (ionizing radiation) agents. In an effort to characterize the chemical exposures, monitoring for chemical hazards was conducted near eleven ion implanters at three integrated circuit facilities, while ionizing radiation was monitored near four of these units at two of the facilities. The workplace monitoring suggests that ion implantation operators routinely are exposed to low-level concentrations of dopants. Although the exact nature of dopant compounds released to the work environment was not determined, area and personal samples taken during normal operating activities found concentrations of arsenic, boron and phosphorous below OSHA Permissible Exposure Limits (PELs) for related compounds; area samples collected during implanter maintenance activities suggest that a potential exists for more serious exposures. The results of badge dosimetry monitoring for ionizing radiation indicate that serious exposures are unlikely to occur while engineering controls remain intact. All emissions were detected at levels unlikely to result in exposures above the OSHA standard for the whole body (1.25 rems per calendar quarter). The success of existing controls in preventing worker exposures is discussed. Particular emphasis is given to the differential exposures likely to be experienced by operators and maintenance personnel.(ABSTRACT TRUNCATED AT 250 WORDS)

Toxicology and occupational hazards of new materials and processes in metal surface treatment, powder metallurgy, technical ceramics, and fiber-reinforced plastics.

“…Ionizing radiation should be measured after an implanter has been installed, and lead shielding should be applied if necessary. However, results of badge dosimetry monitoring of personnel operating ion implanters indicate that serious exposure to ionizing radiation normally does not occur (4).…”

“…For producing wear-resistant tools, the ions (N+, Ti " , Cr " , B+) are produced from nitrogen, titanium tetrachloride, chromium (VI) dioxychloride, and boron trichloride. In the semiconductor industry ion implantation is used to produce arsenic-or phosphide-doped silicon, and the dopant ions are generated from arsine and phosphine (4).…”

Arsenic Exposure during Preventive Maintenance of an Ion Implanter in a Semiconductor Manufacturing Factory

“…During PM tasks, debris may be dispersed in the air and workers can be exposed through inhalation (Choi et al, 2015). Arsenic exposure is a site-specific health hazard for PM workers assigned to cleaning ion implanters because of the use of arsine gas (Ungers and Jones, 1986;De Peyster and Silvers, 1995). Few studies have investigated the level of arsenic present during PM tasks in the semiconductor industry (Park et al, 2010).…”

“…Although most fabrication processes are automated, preventive maintenance (PM) tasks, such as cleaning the ion source and beam path, and troubleshooting of facilities, are performed manually by workers (Ungers and Jones, 1986). PM workers are assumed to have a higher exposure to hazardous agents than workers in other occupational settings (De Peyster and Silvers, 1995;Park et al, 2010;Yoon, 2012).…”

“…Arsenic and arsenic compounds, such as arsine gas, are widely used in the semiconductor and electronics industries (IARC, 2006). Arsenic, which is used as a dopant to create functional units for semiconductor devices because of its high solubility (Ungers and Jones, 1986;Jaeger, 2002), is the main hazardous material in the semiconductor fabrication process (Bender et al, 2007).…”