Studies on the Toxicity, Bioaccumulation and Biopersistence of Model and Commercial Chemical Mechanical Planarization Slurries with Daphnia Magna

Date

2018-08

ORCID

Journal Title

Journal ISSN

Volume Title

Publisher

item.page.doi

Abstract

Nanoparticle (NP) abrasives are components of chemical mechanical planarization (CMP) slurries used to polish wafers of semiconducting materials such as silicon. The semiconductor industry is interested in understanding the potential environmental toxicity associated with CMP NPs because the NPs may be discharged to aquatic ecosystems. However, assessing the toxicity of these specialized CMP NPs is challenging because commercial slurries may contain undefined toxic constituents. In response to this challenge, a manufacturer produced four model CMP slurries comprising colloidal or fumed silicon oxide (c-SiO₂ or f-SiO₈), cerium oxide (CeO₂), or aluminum oxide (Al₂O₃) NPs without known soluble toxicants to permit toxicity assessments of actual NPs used in commercial CMP slurries. This dissertation presents, for the first time, studies on the acute and chronic toxicities, the bioaccumulation, and the biopersistence of model CMP NPs with Daphnia magna (D. magna) – a fresh-water organism used in ecotoxicity assessments. The major findings presented in chapter two are that different model CMP slurries exert distinct effects on D. magna morbidity, growth, and reproductive output, and that the CeO₂ and Al₂O₃ CMP slurries severely reduced D. magna reproduction upon chronic exposure at sub-lethal applied doses, which could have adverse consequences to aquatic ecosystems. The major findings presented in chapter two are that different model CMP slurries exert distinct effects on D. magna morbidity, growth, and reproductive output, and that the CeO₂ and Al₂O₃ CMP slurries severely reduced D. magna reproduction upon chronic exposure at sub-lethal applied doses, which could have adverse consequences to aquatic ecosystems. The major findings in chapter three are that CeO₂ and Al₂O₃ NPs were accumulated in different amounts by D. magna, and that after 48 h of depuration, D. magna exposed to 0.10 mg/mL CeO₂ eliminated 85% of the CeO₂ load, and D. magna exposed to 0.10 mg/mL of Al₂O₃ eliminated 78% of the Al₂O₃ load. The fourth and the final chapter of this dissertation addresses the question of whether polishing a gallium arsenide (GaAs) wafer can impart added toxicity to CMP NPs. Using a commercial c-SiO₂ CMP slurry (Ultra-Sol® 200S), the key findings were that neither the pristine or spent slurry at 0.10 mg/mL c-SiO₂ NPs was toxic after a 21-day exposure, but both slurries led to a slight increase in body size and a ~2-fold increase in reproduction, indicative of a hormetic response. Further testing revealed that the effector was a soluble component(s) in the pristine slurry, and not the pristine or spent NPs.

Description

Keywords

Environmental toxicology, Nanoparticles, Chemical mechanical planarization, Slurry, Abrasives, Daphnia magna

item.page.sponsorship

Rights

©2018 The Author. Digital access to this material is made possible by the Eugene McDermott Library. Further transmission, reproduction or presentation (such as public display or performance) of protected items is prohibited except with permission of the author.

Citation