EUVL defect printability: an industry challenge

Abstract

Extreme ultraviolet (EUV) patterning appears feasible using currently available EUV exposure tools, but some issues must still be resolved for EUV patterning to be used in production. Defects in EUV mask blanks are one such major issue, as evidenced by the research focused on defect printability. Inspection tools are needed to detect phase defects on EUV mask blanks that could possibly print on the wafer. Currently available inspection tools can capture defects on the mask, but they also need to be able to classify possible printable defects. Defect classification for repair and mitigation of printable defects is very difficult using DUV inspection tools; however, if the actinic inspection tool (AIT) could gather defect information from more multilayer stacks, it may be able to separate printable defects from unprintable defects. If unprintable defects could be eliminated, the defect information could be used for mask pattern shifts to reduce printable defects. Fewer defects would need to be repaired if there were a better chance of capturing printable defects using an actinic inspection tool. Being able to detect printable defects on EUV blanks is therefore critical in mask making. In this paper, we describe the characterization of native phase defects in the manufacturing of EUV mask blanks using the state-of-the-art mask metrology equipment in SEMATECH's Mask Blank Development Center (MBDC). Commercially available quartz substrates were used and Mo/Si multilayers were deposited on the substrates to characterize phase defects. Programmed defects of various dimensions were also prepared using e-beam patterning technology on which multilayers were deposited. Transmission electron microscopy (TEM) was used to study multilayer profile changes, while SEMATECH's AIT was used to image defects and predict their printability. A defect library for native defects and printability of programmed phase defects is introduced. Finally technical challenges for EUV defect printability will be discussed.