Toward Reducing CO2 Emissions from Ultra-Pure Semiconductor Gases: A Case Study of TEOS Purification Process Optimization and Renewable Feedstock Utilization

Abstract

This study evaluated the CO₂ emissions associated with the ultra-pure tetraethyl orthosilicate (TEOS), a typical raw material for the deposition of silicon dioxide films on silicon wafers via plasma-enhanced chemical vapor deposition (PECVD). First, we designed a purification process to remove organic impurities, metal contaminants, and particles from TEOS synthesized from metallic silicon. Simulation models were developed to assess the CO₂ emissions of these processes. Among the three purification steps, metal component removal led to the highest CO₂ emissions, and the TEOS recovery ratio was a key parameter for determining the CO₂ emissions. Second, we evaluated the effect of ultra-pure TEOS on CO₂ emissions from the PECVD process. The total CO₂ emissions, including direct emissions, purification-derived emissions, and material-derived emissions, was 23.6 g-CO₂ for deposition on a 300 mm ϕ silicon wafer. Because semiconductor manufacturing requires materials with ultra-high purity, reducing CO₂ emissions by improving the purification efficiency remains challenging. Finally, we explored the potential to reduce CO₂ emissions by replacing the conventional TEOS feedstock (metallic silicon) with a renewable feedstock (rice husk). Modeling indicates that this alternative feedstock could lower CO₂ emissions for depositing on a 300 mm ϕ silicon wafer by 38%, thereby enhancing PECVD sustainability.