SWHL aerial image is not sensitive to local defects of the holographic mask

Holographic mask does not need regular control, maintenance and repair and has extremely long lifetime due to its low sensitivity to local defects and particles (by a factor of 109 – 1011 compared to common projection masks), that might appear during mask manufacturing and exploitation.

In SWHL there is no one-to-one correspondence between mask and image elements thus the effect of local mask defects is almost completely eliminated.

SWHL imaging
SWHM without defects
Defect on the SWHM (0.8% of the total SWHM area)
Image generated by SWHM without defects (half-pitch – 240nm; average line edge roughness – 10nm)
Image generated by a corrupted SWHM (half-pitch – 240nm; average line edge roughness – 16nm)

We investigated influence of other mask defects and defects of optical elements. SWHL imposes much less requirements to optical elements positioning and quality of mask manufacturing.

On the contary, in traditional DUV lithography the problem of local defects is very urgent. Even a small mask defect inevitably leads to ruining of the corresponding section of the image.

DUVL imaging
DUVL mask defect
Corresponding aerial image