1 April 2005 Contact hole formation by multiple exposure technique in ultralow k1 lithography
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J. of Micro/Nanolithography, MEMS, and MOEMS, 4(2), 023005 (2005). doi:10.1117/1.1899324
The double line and space (L&S) formation method with L&S masks and dipole illumination was found to have high capability to fabricate ~0.3 k1 contact hole (C/H) pattern. The procedure was as follows. The first L&S pattern was formed and was hardened to avoid the dissolution and mixing during the second resist coating. The second L&S pattern perpendicular to the first one was formed on the first resist pattern. The common space area of the two patterns became 1:1 C/H pattern. Simulation results showed that the double L&S formation method has much wider lithography latitude than other methods, such as single exposure of a C/H mask with quadrupole illumination, single exposure of a vortex mask with conventional illumination, and double exposure of L&S masks with dipole illumination to a single-layer resist. A 75 nm (0.30 k1) 1:1 C/H pattern was fabricated. An 80 nm (0.32 k1) 1:1 C/H pattern had 280 and 600 nm depth of focus in each resist layer at 8% exposure latitude. Moreover, a new method, in which a C/H mask replaces the L&S masks, is proposed to achieve cost reduction and the same high performance as the L&S masks.
Hiroko Nakamura, Yasunobu Onishi, Kazuya Sato, Satoshi Tanaka, Shoji Mimotogi, Koji Hashimoto, Soichi Inoue, "Contact hole formation by multiple exposure technique in ultralow k1 lithography," Journal of Micro/Nanolithography, MEMS, and MOEMS 4(2), 023005 (1 April 2005). https://doi.org/10.1117/1.1899324

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