Enhancing Filtration Efficiency via Nanofibrillation of Polypropylene Fibers for Advanced Slurry Depth Filters in Semiconductor Manufacturing

The chemical mechanical polishing process utilizes a slurry of fine abrasive particles for planarizing the wafer surface. However, any particulate matter in the slurry that is much larger than the abrasives can cause manufacturing defects such as micro-scratch during the polishing process. Thus, efficient filtration methods are essential to remove these “large” particles from the slurry. Here, we develop a depth filter with a multi-stage pore structure, which is made by using approximately 600 nm thick polypropylene nanofibers produced by the melt-blown method. Unlike conventional filters made of micrometer-thick fibers, the nanofiber filter dramatically increases filtration efficiency and reduces the pressure drop across the filter. While the filtration efficiency of the conventional microfiber filter is 79%, the nanofiber filter reaches 95%. The improved efficiency is attributed to the reduced pore size and enhanced porosity of nanofiber-based media, and along with fewer dead zones compared to the microfiber-based fabric. The polypropylene nanofiber filter significantly improves the slurry quality, reducing the large particle concentration and manufacturing defects in semiconductor manufacturing.