22 March 2011 Self-aligned triple patterning for continuous IC scaling to half-pitch 15nm
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A self-aligned triple patterning (SATP) process is proposed to extend 193nm immersion lithography to half-pitch 15nm patterning. SATP process combines lithography and spacer techniques in a different manner than the conventional selfaligned double patterning (SADP) by keeping the mandrel lines and the second spacers. Compared with other scaling candidates such as self-aligned quadruple patterning (SAQP), it can relax the overlay accuracy requirement of critical layers and reduce their process complexity by using less masks. A 3-mask SATP mandrel recession (SMR) technique is invented to relax the overlay requirement of critical layer patterning. We also successfully demonstrate a 2-mask SATP process concept for patterning critical layers that contain lines/spaces, pads and peripheral circuits, thus opening an opportunity to significantly reduce the process costs. If applied in deep nano-scale IC fabrication, SATP technique will have a fundamental impact on the design methodology of integrated circuits. Using both dry and immersion lithography, we have fabricated half-pitch 21nm and 15nm patterns with a SATP process. It is found that the mandrels (lines) co-defined by lithography and etch processes have worse line width roughness (LWR) than that of spacers, which poses a unique problem to CD control in IC design. As a major focus of our early-stage research, patterning small mandrels/lines in SATP process is a non-trivial challenge. Different materials have been screened and an optimal scheme of mandrel and spacer materials is necessary to meet key requirements (e.g., LER and CDU) of the lithographic performance.
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Yijian Chen, Yijian Chen, Ping Xu, Ping Xu, Liyan Miao, Liyan Miao, Yongmei Chen, Yongmei Chen, Xumou Xu, Xumou Xu, Daxin Mao, Daxin Mao, Pokhui Blanco, Pokhui Blanco, Chris Bencher, Chris Bencher, Raymond Hung, Raymond Hung, Chris S. Ngai, Chris S. Ngai, } "Self-aligned triple patterning for continuous IC scaling to half-pitch 15nm", Proc. SPIE 7973, Optical Microlithography XXIV, 79731P (22 March 2011); doi: 10.1117/12.881645; https://doi.org/10.1117/12.881645

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