7 June 1996 Swing curve characteristics of halftone PSM with off-axis illumination for i-line lithography
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Abstract
In this paper, swing curve characteristics of half-tone PSM (8 percent transmittance) with off- axis illumination are investigated. They are compared with the swing curve features of binary masks under the same off-axis illumination. I-line stepper (0.57NA) is used with annular illumination ((sigma) 0.6-0.4) for HTPSM and binary mask. Equal line and space patterns and isolated line patterns of 0.32 approximately 0.4micrometers CDs are focused to compare the performances of HTPSM and binary mask. Concerning dense lines, the swing heights of HTPSM are reduced that those of binary mask, by more than 20 nm. Isolated lines of both masks showed far severer CD variations than dense lines. The isolated lines of binary mask, of sub-0.35micrometers nominal CDs variations than dense lines. The isolated lines of binary mask, of sub-0.35micrometers nominal CDs, disappeared around the resist thickness for minimum CD. However the isolated lines of HTPSM, of sub-0.35micrometers nominal CDs, survived regardless of resist thickness, although the CD variations were still severe. These improved swing curve features of HTPSM for dense and isolated lines are attributed to the steep aerial image slopes of HTPSM for dense and isolated lines are attributed to the steep aerial image slopes of HTPSM. HTPSM with off-axis illumination is expected to be very profitable particularly for sub-0.35micrometers design rule devices in view of swing effect.
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Yong-Seok Choi, Yong-Seok Choi, Hoyoung Kang, Hoyoung Kang, Woo-Sung Han, Woo-Sung Han, Young-Bum Koh, Young-Bum Koh, "Swing curve characteristics of halftone PSM with off-axis illumination for i-line lithography", Proc. SPIE 2726, Optical Microlithography IX, (7 June 1996); doi: 10.1117/12.240948; https://doi.org/10.1117/12.240948
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