Characterization of airborne nanoparticulate matter in semiconductor manufacturingenvironments

Project: Research project

Project Details

Description

Characterization of airborne nanoparticulate matter in semiconductor manufacturingenvironments Characterization of airborne nanoparticulate matter in semiconductor manufacturingenvironments Semiconductor manufacturing facilities are typically clean environments with specially conditioned air, at low particle concentrations for most of the process (clean room settings). With the growing use of nanosized materials in processes such as chemical mechanical polishing (alumina, ceria, silica), UV photoresists (metal oxides), or thermal packaging (CNTs), there is an emerging concern for occupational exposure to these materials by inhalation if aerosolized in the process. In addition, nanosized particles can be generated by processes such as the wafer polishing and result in inhalation exposure by workers performing tasks in the fab and subfab (e.g. Brenner et al., 2016). While single nanoparticles <100 nm were not identified in this study, captured airborne particulate showed the existence of metal oxide NPs (100 nm-500 nm) as well as aggregates, agglomerates, and larger single particles (>1000 nm) (Brenner et al., 2016). Despite the mixed chemical composition and structure, Brenner et al., 2016b indicated low particulate counts and therefore low potential for worker inhalation exposure to nanoparticles used and/or generated during CMP-related tasks. However, in addition to NP generation during normal operations, preventive maintenance of various fabrication facilities (e.g., CMP, local scrubber, PECVD and ion implanters) may also cause significant release of nanoparticle in the breathing zone of the workers, especially during maintenance of ion implanters and PECVD (Liao et al., 2018). The chemical compositions of the particles coincided with those of the fabrication-related chemicals, indicating the potential exposure to the fabrication-related chemicals through the particles released during the maintenance (Liao et al., 2018). Furthermore, incidental, non-process particles can form at surfaces during the manufacturing process and/or be freed by abrasion (Osborne et al., 2017, Jiang et al., 2015) and even form through nucleation of gas phase contaminants. The nucleation pathway is a largely uninvestigated mechanism in clean rooms. The latter is surprising as in ambient air, nucleation is rather rare as the competitive process of condensation on existing particles, however in clean room environments, there are orders of magnitude less particles to condense on, hence favoring nucleation over condensation for limited volatile compounds like highly oxidized species. Overall air concentrations of nanoparticles are likely low compared to current exposure regulations such as NIOSH maximum total concentration level of 3,000 g/m3 or the existing similar levels for TiO2 or even CNTs. Such concentrations are orders of magnitude higher than anything that would be acceptable for semiconductor manufacturing processes in terms of clean environments. However, these regulations do not really consider nanoparticles specific exposure nor the specific materials used in the semiconductor industry. Currently, no occupational exposure limits (OELs) exists with respect to metal oxide NP used by the semiconductor industry. It is also not known if the existing NIOSH mass-based recommended exposure limits (RELs) are protective for the nanosized material, even though previous studies showed lower than REL concentrations for both silica and alumina (Brenner et al., 2016). Another example is CNT exposure limits, which are based on the same NIOSH standard for Diesel exhaust (e.g. in a bus depot or in coal mines). The fundamental challenge to establishing NP exposure limits is the analytical and capture capability in the composition-specific determination of NPs and their concentrations using existing monitoring and personal protection equipment (PPE). These largely analytical exposure assessment challenges, which have been overlooked relative to the extensive efforts focused on toxicity assessments. We therefore propose to address the following objectives and goals, which will achieved through the tasks outlined below.
StatusFinished
Effective start/end date1/1/1912/31/21

Funding

  • INDUSTRY: Domestic Company: $240,000.00

Fingerprint

Explore the research topics touched on by this project. These labels are generated based on the underlying awards/grants. Together they form a unique fingerprint.