A point of use filter with new pleats design for lithography applications

Point of use filter (POU) has been applied in various applications to remove particle, gels and metal etc. existing in each chemical. Filter start-up performance and particle removal efficiency are key performance metrics for POU, as these metrics can suppress chemical volume and tool down time for filter flushing in lithography process. In this study, we present new pleats design to improve filter start-up performance of POU filter with high-density polyethylene membrane. We used new pleats design to improve fluid flow efficiency, which was validated through flow dP (differential pressure drop) change trend test. Based on this result, the impact of new pleats design on filter cleanliness was tested by organics, metal extraction and initial liquid particle test, and the improvement in filter start-up performance was tested by defectivity evaluation on blanket wafers dispensed with 70/30 PGME/PGMEA solvent filtered through test filter. In defectivity evaluation on blanket wafers, initial defect density of the filter with new pleats design showed over 65% defect reduction comparing with the filter with standard pleats design. After starting dispensing thinner, the filter with new pleats design tended to show gradual defect reduction as increase thinner dispense volume and finally defect counts at 12L thinner dispense volume became less than 10 counts/wafer.