Study on Critical Dimension of Printable Phase Defects Using an Extreme Ultraviolet Microscope: II. Definition of Printable Threshold Region for Hole-Pit Programmed Defects

摘要

This paper is concerned with the observation of phase defects in an extreme ultraviolet lithography (EUVL) mask using an EUV microscope developed by the University of Hyogo. It is very important to determine the type and size of defects on a substrate that are printable after deposition of a multilayer film. Thus, some mask blanks with programmed hole-pit defects with different widths and depths were fabricated by a new process. In addition, critical dimensions of a pit defect were investigated using the EUV microscope. As a result, 4.0-nm-deep hole-pit defects with widths larger than 35 nm were resolved. However, 4.0-nm-deep hole-pit defects with widths smaller than 25 nm were not resolved. On the other hand, 3.0- and 2.0-nm-deep hole-pit defects with widths larger than 60 nm were resolved. However, hole-pit defects with widths smaller than 40 nm were not resolved. Furthermore, the EUVM system was capable of clearly resolving 1.0-nm-deep hole-pit defects with widths larger than 70 nm. However, hole-pit defects with widths smaller than 60 nm were not resolved. From these results, we have determined the size of phase defects that are printable or not by observing phase defects that have various widths and depths on mask blanks utilizing the EUV microscope.