24 March 2016 Mixed-mode, high-order multi-patterning control strategy with small-spot, optical CD metrology on device structures
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Abstract
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.
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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, 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); doi: 10.1117/12.2220782; https://doi.org/10.1117/12.2220782
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