Filter start-up study on HDPE membrane point-of-use filter for lithography application

An effective filter start-up method has been required by semiconductor device manufacturers, mainly in order to reduce waste volume of lithography process chemicals, which become more expensive as lithography technology advances. To quantify filter start-up status, remaining air in the filter was monitored during static-pressure-driven filter start-up using a sub-1 nm rated Pall high density polyethylene (HDPE) membrane filter varying the solvent type. As a result, correlation for the solvent throughput required for filter start-up to the solvent-membrane material affinity defined by Hansen solubility parameter (HSP) was seen. This is similar to Nylon 6,6 membrane filter results in our previous study. There are exceptions such as nBA requires less throughput than dodecane and so does PGME/PGMEA 7/3 mixture than cyclohexanone, while dodecane and cyclohexanone have better affinity to HDPE (=lower HSP distance). These exceptions can be explained by lower viscosity of nBA and PGME/PGMEA 7/3 mixture probably increasing solvent penetration speed into the filter membrane pores. These results show that quicker start-up of HDPE filtration products can be achieved for solvents with higher affinity and lower viscosity.