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24 March 2016 Mixed-mode, high-order multi-patterning control strategy with small-spot, optical CD metrology on device structures
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The high-NA angle-resolved scatterometer YieldStar 1250D, with a small 12x12μm2 inspection area, has been used to inspect CD variation After Develop (ADI) and After Partition/Final Etch (APEI/AFEI) on various layers and features of a HVM DRAM process. During recipe set-up, CD-SEM data were used to verify full recipe quality. The high sampling density enabled by the small inspection area and high speed of the YieldStar angle-resolved scatterometer could be used to reveal various kinds of CD variations. An intra-field control-loop with scanner dose corrections was tested, using very dense ADI and APEI measurements, 400ppf, 4fields. This strategy demonstrated a 21% improvement in intra-field CDU, in line with expectations from predictions. Inter-field control loops with different strategies have been simulated for APEI CD control. To capture all variations in the inter-field fingerprints a dense sampling, 24ppf full wafer, in combination with a dynamic, context-based control strategy, appeared to be necessary. An improvement of 30% of the wafer CDU (excluding the intra-field) is feasible. For the Self-Aligned Double Patterning process, essential for the dense DRAM cells, the CD variation at APEI contributes to pitch-walking at final etch. Pitch walking is an alternating OV error, therefore these control strategies will also contribute to improvement of the OV control budget.
© (2016) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Hugo Cramer, Baukje Wisse, Stefan Kruijswijk, Thomas Theeuwes, Yi Song, Wei Guo, Alok Verma, Rui Zhang, Yvon Chai, Sharon Hsu, Rahul Khandelwal, Giacomo Miceli, Steven Welch, Kyu-Tae Sun, Taeddy Kim, Jin-Moo Byun, Sang-Hoon Jung, Moo-Young Seo, Hyun-Sok Kim, Dong-Gyu Park, and Jong-Mun Jeong "Mixed-mode, high-order multi-patterning control strategy with small-spot, optical CD metrology on device structures", Proc. SPIE 9778, Metrology, Inspection, and Process Control for Microlithography XXX, 97782E (24 March 2016);

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