Risk assessment and safety design improvement for emission gas treatment system in semiconductor manufacturing process

Hydrogen gas is used as a reducing agent in semiconductor manufacturing processes. It suppresses the generation of impurities and oxides while aiding the formation of uniform, high-quality thin films. However, high concentrations of hydrogen gas released after use pose significant fire and explosion risks. Despite this risk, adequate safety design measures have not yet been developed owing to the lack of comprehensive risk assessment studies. This study aimed to assess the risk of an emission gas treatment system used in semiconductor manufacturing and to devise effective safety design measures. Pipe connections and vacuum pumps (particularly sealing elements of high-speed drive components) were identified as potential points of hydrogen gas leakage and classified based on the extent of the zones. Consequently, the extent of the zones was estimated to be less than 1 m, which cannot be verified using the hazardous-area distance estimation chart provided in IEC 60079-10-1:2020 (IEC). Therefore, Computational Fluid Dynamics (CFD) simulations were conducted to identify fire and explosion hazards and to further classify the extent of zones. A Hazard and Operability Study (HAZOP) was conducted to systematically identify potential risk factors within the system. For the identified factors, Layer of Protection Analysis (LOPA) was used to determine the need for additional Independent Protection Layers (IPLs) and to assess conformance with the risk tolerance criterion (<1 × 10⁻⁵). Finally, a safety design plan for the emission gas treatment system was developed, incorporating a Safety Instrumented Function (SIF) to mitigate the identified risks.