25 June 1999 Application of two-wavelength optical heterodyne alignment system in XS-1
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Abstract
This article presents the alignment performance of the two- wavelength optical heterodyne alignment system in the x-ray stepper XS-1. The alignment accuracy obtained by the double- exposure method with a single mask and a Si trench wafer was better than 20 nm. The dependence of the alignment accuracy on Si trench depth indicated that the two wavelengths compliment each other and ensure a 3(sigma) of less than 20 nm. The alignment capabilities for other processed test wafers were also investigated by mix-and-match exposure. For etched SiO2 and poly-Si film on a Si trench, an accuracy below 20 nm was obtained. For AlSiCu film sputtered on etched SiO2, there appeared systematic alignment offsets depended on die position, which are thought to be due to a wafer-induced shift. The systematic offset errors were eliminated by the use of send-ahead wafer and corrections for individual offsets on each die, and thus the alignment accuracy was improved to 20-40 nm for each alignment axis. The two-wavelength heterodyne alignment system of the XS-1 has sufficient potential for 130-nm lithography and below.
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Soichiro Mitsui, Takao Taguchi, Yukiko Kikuchi, Hajime Aoyama, Yasuji Matsui, Masanori Suzuki, Tsuneyuki Haga, Makoto Fukuda, Hirofumi Morita, Akinori Shibayama, "Application of two-wavelength optical heterodyne alignment system in XS-1", Proc. SPIE 3676, Emerging Lithographic Technologies III, (25 June 1999); doi: 10.1117/12.351120; https://doi.org/10.1117/12.351120
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