Airborne nanoparticle filtration in semiconductor manufacturing CFM: Contamination free manufacturing

This paper shows results from condensation particle counter for typical H14 & U15 filtration media (>99.995%, resp. >99.9995% efficiency at most penetrating particle size (MPPS)) using different raw materials and designs, down to 20 nm particle sizes. We demonstrate that glass fiber (GF) materials display very high nanoparticle removal efficiency compared to commercially available polytetrafluoroethylene (PTFE) based membranes thanks to its 3-dimensional fiber structure and the diffusion behavior of airborne nanoparticles. It shall also be noted that in all tested samples, the MPPS for PTFE membranes was in the range of 50 to 90 nm, well below the traditionally accepted range observed for GF based HEPA & ULPA filters (100–300 nm) and as outlined by the EN1822 standard. Below 50 nm the performance gap between glass and membrane materials is so high that the industry should be considering this difference when implementing new materials and processes generating nanoparticles or sensitive to nanoparticles. It is highly probable that semiconductor manufacturers do not have access to relevant filter performance information when assessing the risks associated with nanoparticle concentrations in different processes as extrapolations below MPPS is not explained in standard industrial filter QC reports. While PTFE membranes may provide energy efficient solutions to facility systems, end users shall be aware that higher nanoparticle counts will be measured below membrane materials when compared to GF based solutions.