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Proceedings Paper

Large assist feature phase-shift mask for sub-quarter-micrometer window pattern formation
Author(s): Shinji Ishida; Tadao Yasuzato; Hiroyoshi Tanabe; Kunihiko Kasama
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Paper Abstract

To improve the depth of focus of isolated windows, large assist feather technique has been proposed. This large assist method uses the assist features having almost the same size as main patterns, and the quartz substrate was vertically etched at the assist features. These large assist features were not printed on a wafer by mask topography effect; that is, the light intensity at large assist feature was decreased by the scattering effect of the vertical quartz edges. In this large assist feature masks, the phase shift angle of an assist feature has large effect on focus latitude. We chose two phase shift angles: 180 degrees for small sigma illumination and 360 degrees for annular illumination. The performances of two large assist feature masks were evaluated by using a 0.55 NA, valuable sigma, and KrF excimer laser stepper. Moreover, we applied surface insoluble layer to the assist feature method. Large assist features having the same size as main patterns were not printed on resist surface for 0.16 - 0.2 micrometer windows. Wide DOF (0.8 micrometer) of 0.16 micrometer window was obtained by using this method.

Paper Details

Date Published: 28 July 1997
PDF: 11 pages
Proc. SPIE 3096, Photomask and X-Ray Mask Technology IV, (28 July 1997); doi: 10.1117/12.277278
Show Author Affiliations
Shinji Ishida, NEC Corp. (Japan)
Tadao Yasuzato, NEC Corp. (Japan)
Hiroyoshi Tanabe, NEC Corp. (Japan)
Kunihiko Kasama, NEC Corp. (Japan)

Published in SPIE Proceedings Vol. 3096:
Photomask and X-Ray Mask Technology IV
Naoaki Aizaki, Editor(s)

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