Semiconductor nanocrystals, also called quantum dots (QDs), have been proven as powerful fluorescent probes. This paper presents a new method to evaluate the retention efficiency of nanofiltration membranes using sub-10 nm fluorescent QDs in organic solvents. Two different Cd-based QDs with uniformed sizes (nominal 8 nm and 4 nm) were used as challenge particles in this study. Fluorescence spectrophotometer was used as a detector to measure the QDs concentration before and after filtration. High resolution transmission electron microscope (HRTEM) and dynamic light scattering (DLS) were employed for measuring particle size and size distribution, which revealed the QDs used in this study were with a narrow size distribution. Three different types of Entegris UPE membranes were tested by using this method. The filters were rated at 3 nm, 5 nm and 10 nm using bubble-point extrapolative methods were further confirmed by the QDs retention tests in solvents.
In its relatively short history of use, the formulation complexity of bottom anti-reflective coatings (BARC) for semiconductor fabrication has become an enabling technology for nanoscale chip geometries. As lithography advancements are mastered, process material and equipment capabilities must follow. Typical photochemical solutions contain a variety of additives, often in trace amounts. The slightest unintended alteration of the photochemical formulation's chemical composition could have a detrimental effect on lithography process yield. The added complexity of BARC formulations leads suppliers of liquid microcontamination control technologies to develop filtration solutions that effectively remove the destructive particles and gels from BARC while maintaining the formulation's integrity during the filtration process.
In a joint study, Entegris and Brewer Science discovered that nylon has proven to be less chemically resistant to attack by certain BARC materials than next-generation ultrahigh molecular weight polyethylene (UPE) membrane materials. Essentially, UPE membrane-based filters remove the damaging particulate and gels without altering the delicate chemical formulation of BARC materials. It has also been experimentally proven that the UPE-based membrane maintains its material integrity during the filters' lifetime. This provides new opportunities for fabs and photochemical suppliers to enhance the performance, repeatability and reliability of semiconductor lithography processes.