Removal of 12-nm Particles from High-Purity Water by a Combination of Ultrafiltration and Microfiltration
By Donald C. Grant, Dennis Chilcote, Ph.D., and Uwe Beuscher, Ph.D.
The critical feature size of state-of-the-art semiconductor devices is on the order of 30 nanometer (nm) and expected to decrease to < 20 nm by 2015 (1). Particles on the order of half this feature size in the ultrapure water (UPW*) used during device manufacturing can reduce manufacturing yield and finished device reliability. Microfiltration (MF) and ultrafiltration (UF) devices with particle removal ratings below 50 nm are often used to control particle concentrations in the process water used in device manufacturing. The ability of these filters to remove particles is typically measured using optical particle counters (OPCs), which have reached a practical measurement limit of 40 nm with a counting efficiency of only a few percent at this size. This size detection is considerably above the critical size for current and future semiconductor device technologies. Therefore, this metrology is unable to confirm the presence of damaging particles, and leaves the semiconductor manufacturers unaware of whether the filtration strategy used in the UPW systems is removing these small particles.
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