Abstracts Category : Other

Potential Environmental and Health Risks from Nanoparticles and III-V Materials Used in Semiconductor Manufacturing

by Chao Zeng

Nanoparticles (NPs) have unique electronic, optical and chemical properties due to the extreme small size. Engineered nanoparticles (ENPs) are intentionally produced for desired applications, with specific properties related to shape, size, surface properties and chemistry. Nano-sized silica (SiO2), alumina (Al2O3) and ceria (CeO2) are three important ENPs with large production and wide applications. One of the principal uses of these ENPs is in chemical and mechanical planarization (CMP), a key process applied to polish wafers when fabricating integrated circuits in semiconductor manufacturing, in which SiO2, Al2O3 and CeO2 NPs are used as abrasive particles in CMP slurries. CMP generates large amounts of waste effluents containing high levels of ENPs. Some ENPs have been proven to be able to cause toxicity to microorganisms and higher life forms, including humans. Therefore, there are concerns about the potential risks that ENPs may pose to the natural environment and human health. In addition, III-V materials like indium arsenide (InAs) and gallium arsenide (GaAs) are increasingly used in electronic and photovoltaic devices. Besides ENPs, the waste streams from III-V manufacturing also contain dissolved and particulate materials removed from III-V films during CMP. Arsenic is one of the most notorious contaminants that has been widely studied, while only very limited ecotoxicity information is available for gallium and indium. Finally, since ENPs have high surface area, it is very likely they will interact with the soluble species (such as arsenic ions) in CMP wastewater. Therefore, it is of great importance to understand whether the interactions between these materials could alter their fate and toxicity. The objective of this work is to investigate the potential environmental and health risks from the ENPs and III-V materials used in semiconductor manufacturing. To this end, the physical, chemical and toxicological characterization of ENPs used in CMP was performed (Chapter 3). Furthermore, the fate and transport of the most used ENP, SiO2, in porous media was studied (Chapter 4). In addition, acute toxicity of As(III), As(V), In(III) and Ga(III) species was evaluated using different bioassays (Chapter 5). Finally, the cytotoxicity of ENPs used in CMP slurries to human lung bronchial epithelial cells was evaluated using an impedance based real time cell analysis (RTCA) assay (Chapter 6). In Chapter 3, four model slurries containing ENPs including colloidal silica (c-SiO2), fumed silica (f-SiO2) cerium oxide (CeO2) and aluminum oxide (Al2O3) were characterized for their physical, chemical and toxicological properties. Ecotoxicity of these slurries to the marine bacterium, Aliivibrio fischeri, was evaluated by measuring its bioluminescence activity as a function of the ENP concentration dosed. The results showed that f-SiO2 and CeO2 were not toxic at concentrations up to 700 and 1000 mg/L, respectively. On the other hand, c-SiO2 and Al2O3 were inhibitory only at very high concentrations (>600 mg/L). At about 1300Advisors/Committee Members: Sierra-Alvarez, Reyes (advisor), Sierra-Alvarez, Reyes (committeemember).