Continuous Improvements and Future Challenges of Air Pollution Control at an Advanced Semiconductor Fab

This study reviews the air pollution control strategy at an advanced semiconductor fab focusing on its continuous improvements and future challenges. A wide range of air pollutants is emitted from various sources classified as organic solvents, corrosive, toxic and combustible gases. This effective strategy employs a two-stage treatment method to comply with national emission regulations. Eight different types of local scrubbers (typ. gas flow rate: 0.3-2.0 CMM for the dry type or 60-83.3 CMM for the wet type) are used as pre-treatment devices at the first stage to remove specific target pollutants with high concentrations emitted from process chambers. Exhaust gases from local scrubbers are then grouped and further treated by central control facilities at the second stage, including the dual zeolite rotor-concentrator plus the thermal oxidizer for VOCs (typ. gas flow rate: 2500 CMM), the dual-central wet scrubbers (CWS) and alkaline CWS (typ. Gas flow rate: 2000 CMM) for acid and alkaline gases, respectively. After the two-stage treatment, the removal efficiency of the VOCs can reach higher than 98.4%, surpassing the emission standard of 90%. The design parameters and operating conditions of the CWSs meet the criteria set in the emission standard for the semiconductor industry. In the future, CWS performance can further be improved by using advanced structured packing materials with larger specific surface areas to shorten the residence time and lower the chemical dosing amount and pressure drop while achieving higher removal efficiency for acid and alkaline gases at a reduced operating cost. The challenges to removing derived fine PM and white smoke still remain which can be resolved by using efficient control devices in the pre- and post-treatment stages, such as wet electrostatic precipitators. Finally, the by-product NOx can be minimized by using low-NOx burners or de-NOx control technologies in the future.