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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 and 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 deep ultraviolet (DUV) inspection tools; however, if the actinic inspection tool (AIT) could gather defect
information from more multilayer (ML) 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 programmed ML 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). Programmed defects of various dimensions were prepared using e-beam patterning technology and Mo/Si
MLs were deposited with SEMATECH's best known method (BKM) and pit smoothing conditions on programmed
defects to characterize ML phase defects. Atomic force microscopy (AFM) and transmission electron microscopy
(TEM) were used to study ML profile changes, while SEMATECH's AIT was used to image ML phase defects and
predict their printability. Multilayer defect reconstruction (MDR) was done using AFM images, which were then
compared to TEM images. Defect printability simulation (DPS) was used for comparison to AIT through-focus
images. 22 nm, 27 nm, and 32 nm line and space (L/S) absorber patterns were positioned on top of programmed
ML phase defects and simulated defect printability. The ML phase defects are located at the edge of L/S patterns
and at the center of space patterns and Bossung plot was used to separate printable defects from unprintable defects.
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