Metal ions in photoresists and solvents pose an ever greater contamination problem in photolithography’s advanced applications. The reduction of metal contaminants is critical in the entire photochemical supply chain. In this paper we demonstrate that two novel membrane purifiers dramatically reduced the metal contents in a range of organic solvents. These solvents are used for photoresist manufacturing and for wafer surface and dispense line rinse in track tools. The impact of flow rate and metal concentrations in the feed on the metal removal efficiency of the purifiers is presented. Furthermore, a study to determine the dominant mechanism of metal reduction in solvents is proposed.
Defect source reduction in leading-edge iArF resists is a critical requirement to improve device performance and overall yield in lithography manufacturing processes. It is believed that some polar polymers can aggregate and be responsible for single or multiple micro-bridge defects. Further investigation into the formation of these defects is needed. We have previously presented the effective removal of gel-like polymers using nylon media . However, as the industry is moving to smaller feature sizes, there is a need to further improve the defect removal efficiency. In this paper, a filter, comprised of a novel membrane called Azora with unique morphology and high flow performance is introduced. This new filter shows better on-wafer in an advanced ArF solution than conventional Nylon and UPE media. In addition, it shows improved stability during chemical storage. Results and possible retention mechanisms are discussed.
Weak-polar solvents like PGMEA (Propylene Glycol Monomethyl Ether Acetate) or CHN (Cyclohexanone) are used to dissolve hydrophobic photo-resist polymers, which are challenging for traditional cleaning methods such as distillation, ion-exchange resins service or water-washing processes. This paper investigated two novel surface modifications to see their effectiveness at metal removal and to understand the mechanism. The experiments yielded effective purification methods for metal reduction, focusing on solvent polarities based on HSP (Hansen Solubility Parameters), and developing optimal purification strategies.
Recently nylon filters have been widely implemented in photolithography processes to improve the
yields because many IC and photoresist manufacturers have empirical evidence indicating that the
nylon membrane can adsorb impurities. However, the mechanism by which the nylon membrane
reduces defects is unclear. It is useful to study different defect-causing mechanisms by focusing on the
particular components of photoresists. In this paper various adsorption tests were performed utilizing
surface modification and different photoresist components to measure the effect of nylon membranes
on resist properties, including surface tension, PAG (photoacid generator) concentration and quencher
concentration. Ultimately, the study hopes to determine the most effective way to increase yields by
focusing on how to best implement a nylon filtration strategy.