Printability of buried mask defects in extreme UV lithography

Abstract

A programmed-defect mask consisting of both bump-and pit-type defects on the LTEM mask substrate has been successfully fabricated. It is seen that pit-type defects are less printable because they are more smoothed out by the employed MLM deposition process. Specifically, all bump-type defects print even at the smallest height split of 1.7 nm whereas pit-type defects print only at the largest depth split of 5.7 nm. At this depth, the largest nonprintable 1D and 2D defect widths are about 23 nm and 64 nm, respectively.

Exploring probability of shallow ML defect impact to defect assurance

“…In the past, several evaluation results of programmed ML defects which were fabricated by e-beam writing and etching process have been reported. 3,4 In these reports, normally the cross-section shape of the programmed defects are rectangle. On the other hand, very curious result are reported that defect printability and defect detectability of rectangular shape programmed defects and natural defects are very different.…”

Implementable and systematic mitigation of native defects in EUV masks

“…In a previous study [1], defects resulting from bumps and pits programmed in the LTEM substrate were used to find correlation with lithographic results on wafer. Combining the results obtained in that study with existing methods of mitigating EUV native defects [2,3], we propose a novel method which can identify the location of EUV native defects and then shift the layout pattern to avoid their printing on wafer.…”