24 July 2002 Importance of resist transparency and development rate control in via-first dual damascene processes
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We have investigated the requirements for resist materials in via-first dual damascene copper processes. We first patterned vias on a dielectric stack, and then, after via etching and stripping, we formed metal trench patterns using KrF/ArF lithography. A bottom anti-reflective coating (BARC) was used to fill the vias prior to the resist coating in order to protect the bottom of the vias during the trench etching. Trench patterns were formed on the BARC using chemically amplified resists. We found that resists with lower transparency and a lower maximum development rate (Rmax) were not developed in the vias on the partially filled BARC. When the trench patterns were etched with resist residue in the vias, severe fence defects were observed around the via openings at the bottom of the trenches. These defects cannot be removed by dry or wet stripping. Complete removal of the resists in the vias prevented the formation of fences. Simulation of the resist profile showed the use of resists with high transparency and a high Rmax prevented the accumulation of resist residue in the vias. A KrF resist formulated with higher transparency and a higher Rmax was completely developed even in the vias, so that trench patterns without the fences were formed after trench etching.
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Seiji Nagahara, Seiji Nagahara, Masashi Fujimoto, Masashi Fujimoto, Mitsuharu Yamana, Mitsuharu Yamana, Takeo Hashimoto, Takeo Hashimoto, } "Importance of resist transparency and development rate control in via-first dual damascene processes", Proc. SPIE 4690, Advances in Resist Technology and Processing XIX, (24 July 2002); doi: 10.1117/12.474259; https://doi.org/10.1117/12.474259

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