Supercritical Carbon Dioxide in Microelectronics Manufacturing: Marginal Cradle-to-grave Emissions

This paper presents and discusses the marginal cradle-to-grave environmental impacts of using VLSI grade supercritical carbon dioxide (scCO2) as a rinsing agent in place of ultrapure water (UPW) in semiconductor fabrication. Impacts are estimated using a consequential life cycle assessment framework for recovered CO2. Upon factoring the cumulative yields of the CO2 recovery and purification processes, compressor energy use (566 kJ/kg CO2 output) together with refrigeration (540 kJ/kg CO2 output) accounts for about 90% of total on-site electricity use. Upstream emissions from production of propylene carbonate co-solvent contribute to more than 50% of the life cycle impacts of scCO2-based wafer cleaning. Overall impacts of scCO2-wafer cleaning, particularly water and energy use, are found to be significantly lower than UPW.