Actinic Inspection of EUV Programmed Multilayer Defects andCross-comparison Measurements Page: 4 of 14
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EIPBN 2006, K. A. Goldberg, et al.,
annular pupil subtending 0.1 to 0.2 numerical aperture (NA), aligned at normal incidence to the
mask. The objective projects the darkfield image onto a low-noise scientific grade charge-
coupled device (CCD) where an entire image field is recorded at once. Careful calibrations are
performed to normalize the recorded signal [11]. The MIRAI tool was able to detect all of the
programmed defects with a high signal-to-noise ratio (SNR) and also noted the presence of a few
"native" defects that appeared after the measurements presented here.
B. The Berkeley actinic inspection tool. The Berkeley actinic inspection system [12], operated
by Goldberg, Barty and Liu, illuminates the mask with EUV light yet records data in a much
different manner than the MIRAI tool. A bending magnet beamline at LBNL's Advanced Light
Source provides monochromatic illumination to a pinhole; a 20x-demagnification Schwarzschild
objective re-images the illuminated pinhole onto the upward-facing reticle with a 60 angle of
incidence. During measurement, the beam focus remains stationary while the mask is translated
and rotated (r, 0) in a manner that allows a portion of the mask to be scanned. Using different
pinhole diameters, the beam size on the reticle can be varied from 1 pm to 5 pm: these
measurements were made with a 2.5-pm diameter beam.
The Berkeley inspection system is flexible in its detector geometry, and is capable of
simultaneously recording brightfield and darkfield signals at up to 100kHz. The inspection data
presented here was recorded with a new detector design that records darkfield light in an off-axis
angular range of 0.6 -35 from the central ray in one direction, and 4.30 in the perpendicular
direction, and with no intervening mirrors between the mask and the detector. In this way the
darkfield detection comes close to the specular beam; the detector was positioned to provide
optimal SNR for the defects in this study.
C. Two Lasertec inspection tools. The test mask was also measured in two non-EUV inspection
tools, both created by Lasertec Corp., and operated for these measurements by Kearney.
The Lasertec M1350, introduced in 2002, uses an argon-ion laser to generate light at the
488-nm illumination wavelength. The scanning confocal system uses a Multiple Image
Acquisition for Giga-bit Inspection with Confocal System (MAGICS) configuration to achieveElectronic mail: KAGoldberg@lbl.gov
ID#: 218, Session 4A.3
4/14
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Goldberg, Kenneth A.; Barty, Anton; Liu, Yanwei; Kearney,Patrick; Tezuka, Yoshihiro; Terasawa, Tsuneo et al. Actinic Inspection of EUV Programmed Multilayer Defects andCross-comparison Measurements, article, January 1, 2006; Berkeley, California. (https://digital.library.unt.edu/ark:/67531/metadc901769/m1/4/: accessed May 8, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.