Environmental Impact and Speciation Analysis of Chemical Mechanical Planarization (CMP) Waste Following GaAs Polishing

Abstract

Chemical Mechanical Planarization (CMP) is a key enabling process used in semiconductor manufacturing to achieve local and global planarization of layers. Contemporary CMP process use nanoparticle slurries for the chemical and mechanical removal of material. As traditional silicon nears its scaling limits, next-generation devices will require the use of III-V materials such as Gallium Arsenide (GaAs). Planarization of GaAs increases Ga and As levels in wastewater, influencing the potential for environmental safety and health (ESH) concerns. Little is known about the environmental fate, behavior, and biological impact of this waste. Specific As species have vastly different magnitudes of toxicity. For example, inorganic As is more toxic than organic species and As(III) is much more toxic than As(V). As(III) is also more difficult to remove from wastewater and is typically oxidized to As(V) before removal. Knowing which specific As species are present in GaAs CMP waste is important for waste treatment and discharge. By measuring As species from a variety of GaAs CMP process conditions, we can discern the key factors affecting the balance of As(III) and As(V) in the CMP waste. In this work, we report on the ESH impacts of GaAs CMP waste, specifically on the (a) presence and speciation of Arsenic in the wastewater effluent; (b) presence and condition of Gallium; (c) physicochemical properties of the slurry nanoparticles after polishing; (d) effect of the slurry on typical oxidation methods and (e) effect of collected CMP wastes on human health, primarily cytotoxicity. The results from this research will help determine the specific effects of CMP slurry and processing conditions on wastewater containing elevated levels of Arsenic as well as provide insight on the type and relevance of remediation methods. Figure 1