Industrial Hygiene Air Monitoring Techniques in Photolithography
Ellen C. Gunderson, CIH, CSP - Advanced Micro Devices (SSA Journal Volume 12 Number 3 - Fall 1998 pp. 17 - 21 )
Continuous air monitoring applications with portable monitors have been used successfully to improve the characterization of workplace airborne solvent levels and associated odors in photolithography areas. The results validated previous data showing extremely low airborne levels of cleaning solvents and photoresist solvents. Resulting data helped facilitate corrective actions to reduce solvent levels and odors even further. In one application, extensive monitoring was conducted with a portable gas chromatograph in response to periodic odors. The major solvents detected included acetone, isopropanol, and propylene glycol monomethly ether acetate (PGMEA). Airborne solvent levels found were typically in the parts per-billion range, and quite variable throughout a work shift depending on work activities. During normal operations, higher solvent levels usually occurred during short term cleaning operations conducted by technicians in non-exhausted areas. In another application, a portable photoionization monitor used with a datalogger continuously monitored airborne solvent levels at an exhausted photolithography maintenance sink. Monitoring results helped in the design of a new improved sink, and in the development of improved procedures to reduce potential solvent exposures. Monitoring conducted after the new sink installation showed a significant and measurable improvement in reducing airborne solvent levels over the previous operation.