Advantages to point of use filtration of photoresists in reducing contamination on the wafer surface

The trends toward narrower line widths in IC manufacture has placed an ever increasing burden on contamination control in every aspect of semiconductor fabrication. Point-of-use (POU) filtration of photoresists has been used to control particle contamination on the wafer surface during coating operations. The need for tighter filtration has led to the introduction of 0.05 μm as well as the traditional 0.10 μm membranes to control contamination during photoresist dispensing. With the introduction of tighter membranes for use in photoresist filtration, the end-user may have concerns that the photoresist may suffer some deleterious effects by undergoing filtration. This study centers on the use of 0.05 μm and 0.10 μm Pall Falcon(R) filters in dispensing Microposit S1813 photoresist for reduction of surface defects on the wafer surface. The results of gel permeation chromatography (GPC) on filtered and unfiltered photoresist showed no effect on the molecular weight of the photosensitive components. Viscosity and coating thickness results indicated no loss in solids that would have an effect on the viscosity and in turn the coating thickness on the wafer surface. G-line exposure demonstrated retention of photospeed, indicating no damaging effects on resin or photosensitive components. The applications of filtration to photoresist dispensing are demonstrated as a positive step to lowering contamination on the wafer surface without deleterious effects on the performance of the photoresist