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12 May 2005 Optimization of multi-pole aperture for via patterning of 90 nm logic devices by KrF lithography
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Optical resolution limit is one of the concerns for exposure tool selection. ArF lithography tools are the first choice for critical layers of 90 nm node with pitches narrower than 280 nm. However, high cost of ArF tools and photoresists make IC manufacturers try to seek for alternatives. Extension of KrF lithography has been widely discussed. For mass production of 130 nm node, KrF lithography has been pushed hard to achieve 160 nm contact holes with 320 nm pitch. In this paper, printing of via holes with the minimum pitch of 280 nm has been demonstrated with a special designed multi-pole aperture and high NA KrF lithography. With these illumination settings, reasonable process windows through all the pitches can be achieved for mass production of 90 nm node logic devices. Multi-pole illumination aperture settings are critical for balancing through-pitch process margins. Forbidden regions should not be found with optimum multi-pole illumination settings. In other words, the adequate combinations of multi-pole sizes and locations can minimize the forbidden proximity behavior and also keep the aerial imaging contrast balance through all the pitches. Mask bias is another factor to enlarge the common process windows. The process margin depth of focus (DOF) and mask enhanced error factor (MEEF) are investigated with various multi-pole settings and mask biases. Simulation works have been done for fine-tuning of the multi-pole aperture to reduce through pitch MEEF and optimize mask biases.
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Shu Ping Fang, Hsiang Yang, Hsien-an Chang, Paul Chiang, Benjamin Sue-Min Lin, and Kuei-Chun Hung "Optimization of multi-pole aperture for via patterning of 90 nm logic devices by KrF lithography", Proc. SPIE 5754, Optical Microlithography XVIII, (12 May 2005);

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