Toward Reducing CO ₂ Emissions from Ultra-Pure Semiconductor Gases: A Case Study of TEOS Purification Process Optimization and Renewable Feedstock Utilization

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.