First measurements of the number size distribution of 1–2 nm aerosol particles released from manufacturing processes in a cleanroom environment. Issue 6 (3rd June 2017) - Ahonen, L. R.
ABSTRACT: This study was conducted to observe a potential formation and/or release of aerosol particles related to manufacturing processes inside a cleanroom. We introduce a novel technique to monitor airborne sub 2 nm particles in the cleanroom and present results from a measurement campaign during which the total particle number concentration (>1 nm and >7 nm) and the size resolved concentration in the 1 to 2 nm size range were measured. Measurements were carried out in locations where atomic layer deposition (ALD), sputtering, and lithography processes were conducted, with a wide variety of starting materials. During our campaign in the clean room, we observed several time periods when the particle number concentration was 10 5 cm −3 in the sub 2 nm size range and 10 4 cm −3 in the size class larger than 7 nm in one of the sampling locations. The highest concentrations were related to the maintenance processes of the manufacturing machines, which were conducted regularly in that specific location. Our measurements show that around 500 cm −3 sub 2 nm particles or clusters were in practice always present in this specific cleanroom, while the concentration of particles larger than 2 nm was less than 2 cm −3 . During active processes, the concentrations of sub 2 nm particles could rise to over 10 5 cm −3 due to an active new particle formation. The new particle formation was most likely induced by a combination of the supersaturated vapors, released from the machines, and the very low existing condensation sink, leading to pretty high formation rates J 1.4 nm = (9 ± 4) cm −3 s −1 and growth rates of particles (GR1.1–1.3 nm = (6 ± 3) nm/h and GR1.3–1.8 nm = (14 ± 3) nm/h). Copyright © 2017 American Association for Aerosol Research