Reduced tolerance for defectivity is a well-documented consequence of the semiconductor industry's constant progress toward smaller IC device dimensions. Among all manufacturing functional areas, photolithography is arguably the most sensitive to process defects, and thus, strongly influences manufacturing process yield. Microbridging is a well-known type of "killer" defect that can become prevalent in KrF and ArF photoresist systems. When present in BEOL lithography layers, bridge defects can manifest as catastrophic, single-line open circuit faults ("opens") in the metal lines of the finished device. Previous work in BARC + resist systems has demonstrated the effectiveness of improved filtration in reducing bridge defects. The present work evaluates the impact of improved filtration on both litho defectivity and device yield. Application of asymmetric nylon 6,6 filters to a bi-layer resist yielded a significant reduction in microbridge defects via removal of gel-like particle defect precursors. Ultimately, these changes are responsible for two-thirds of baseline defectivity reduction in single-line opens. The same benefits are realized-though via a different mechanism-when all-fluoropolymer filters are introduced for a post-develop rinse, which uses ultrapure water (UPW) that is ozonated to 50ppb. Filtration is applied both to the water point-of-supply and at point-of-use. Over time, a significant reduction in microbridge defects-caused by residual developed resist-was realized for several BEOL KrF litho layers. As with the bi-layer resist process, enhanced filtration contributes significantly (36%) to reduction in the single-line opens defect baseline.

Date Published: 1 April 2009
PDF: 10 pages
Proc. SPIE 7273, Advances in Resist Materials and Processing Technology XXVI, 72730O (1 April 2009); doi: 10.1117/12.814374

Published in SPIE Proceedings Vol. 7273:
Advances in Resist Materials and Processing Technology XXVI
Clifford L. Henderson, Editor(s)