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Two versions of a specific 2 nm rated filter containing filtration medium and all other components produced from high density polyethylene (HDPE), one subjected to standard cleaning, the other to specialized ultra-cleaning, were evaluated in terms of their cleanliness characteristics, and also defectivity of wafers processed with photoresist filtered through each. With respect to inherent cleanliness, the ultraclean version exhibited a 70% reduction in total metal extractables and 90% reduction in organics extractables compared to the standard clean version. In terms of particulate cleanliness, the ultraclean version achieved stability of effluent particles 30nm and larger in about half the time required by the standard clean version, also exhibiting effluent levels at stability almost 90% lower. In evaluating defectivity of blanket wafers processed with photoresist filtered through either version, initial defect density while using the ultraclean version was about half that observed when the standard clean version was in service, with defectivity also falling more rapidly during subsequent usage of the ultraclean version compared to the standard clean version. Similar behavior was observed for patterned wafers, where the enhanced defect reduction was primarily of bridging defects. The filter evaluation and actual process-oriented results demonstrate the extreme value in using filtration designed possessing the optimal intrinsic characteristics, but with further improvements possible through enhanced cleaning processes.

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Photolithography is a key technology driver enabling next generation processes. As line widths decrease to 0.18 tm and below, the critical size ofparticulate contamination decreases proportionately. The implementation of filtration below O.ljim within existing dispense systems raises concern as the removal rating of the filter approaches the size of large molecular weight components of the photoresist.This study was undertaken in order to determine the effects, if any, of 0.05 im and fmer filtration on photoresist performance. Utilizing 248 nm DUV resist, filters were tested in two latest generation dispense pumps, one nitrogen pressurization, and the other having a stepper motor arid diaphragm. The coated 200 mm wafers were exposed at increasing exposure dose and focus in a DUVscanner to produce 0. 1 8 jtm features.This study concludes that as the filter removal rating 'became fmer, the resist performance in terms of photospeed, process window or thermal stability did not change. This indicates that, using existing dispense systems, photoresists can be filtered as fme as 0.03 jtm without significant polymer shearing or the unintentional removal of important materials from the resist. Based on these data, appropriate protection in terms of particle removal is possible as line widths necessitate the use of fmer filters in resist dispense pumps.

No abstract