Nanoparticles separation by different conditions at asymmetric flow field- flow fractionation

As semiconductor manufacturing enters the era of sub-10 nm and 3D stacking, “cleanliness” in the process becomes a crucial factor for process yield. The measurement of nanoparticle concentration, size, and shape in various solutions that may cause contamination during the manufacturing process is currently an important research topic. Although there are various nanoparticle measurement techniques available, further technological development and breakthroughs are still needed for measuring low concentrations and complex mixtures of nanoparticles. Therefore, in this study, we attempted to address the measurement challenges posed by mixed particles by applying Asymmetric Flow Field-Flow Fractionation (AF4) in combination with Dynamic Light Scattering (DLS) and Ultraviolet (UV). The strategy involved separating the samples before measurement. For a nanomixture containing five different sizes of gold nanoparticles (AuNPs) with diameters of 20 nm, 40 nm, 60 nm, 80 nm, and 100 nm, three different methods were employed to control the driving force for particle separation during the elution stage: constant cross flow rate, linearly decreasing cross flow rate, and exponentially decreasing cross flow rate. The results demonstrated that different flow rate control methods indeed yielded variations in nanoparticle separation, with the constant flow rate method showing the best separation efficiency. Additionally, it was observed that the thickness of the experimental chamber played a significant role in affecting the retention time of the nanoparticles during separation.