In this study, the integrity and the benefits of the DSA shrink process were verified through a via-chain test structure, which was fabricated by either DSA or baseline litho/etch process for via layer formation while metal layer processes remain the same. The nearest distance between the vias in this test structure is below 60nm, therefore, the following process components were included: 1) lamella-forming BCP for forming self-aligned via (SAV), 2) EUV printed guiding pattern, and 3) PS-philic sidewall. The local CDU (LCDU) of minor axis was improved by 30% after DSA shrink process. We compared two DSA Via shrink processes and a DSA_Control process, in which guiding patterns (GP) were directly transferred to the bottom OPL without DSA shrink. The DSA_Control apparently resulted in larger CD, thus, showed much higher open current and shorted the dense via chains. The non-optimized DSA shrink process showed much broader current distribution than the improved DSA shrink process, which we attributed to distortion and dislocation of the vias and ineffective SAV. Furthermore, preliminary defectivity study of our latest DSA process showed that the primary defect mode is likely to be etch-related. The challenges, strategies applied to improve local CD uniformity and electrical current distribution, and potential adjustments were also discussed.
Cheng Chi, Chi-Chun Liu, Luciana Meli, Jing Guo, Doni Parnell, Yann Mignot, Kristin Schmidt, Martha Sanchez, Richard Farrell, Lovejeet Singh, Tsuyoshi Furukawa, Kafai Lai, Yongan Xu, Daniel Sanders, David Hetzer, Andrew Metz, Sean Burns, Nelson Felix, John Arnold, and Daniel Corliss, "Electrical study of DSA shrink process and CD rectification effect at sub-60nm using EUV test vehicle," Proc. SPIE 10146, Advances in Patterning Materials and Processes XXXIV, 101460Q (Presented at SPIE Advanced Lithography: March 01, 2017; Published: 13 April 2017); https://doi.org/10.1117/12.2260454.
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