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.
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Hugo Cramer, Hugo Cramer, Baukje Wisse, Baukje Wisse, Stefan Kruijswijk, Stefan Kruijswijk, Thomas Theeuwes, Thomas Theeuwes, Yi Song, Yi Song, Wei Guo, Wei Guo, Alok Verma, Alok Verma, Rui Zhang, Rui Zhang, Yvon Chai, Yvon Chai, Sharon Hsu, Sharon Hsu, Rahul Khandelwal, Rahul Khandelwal, Giacomo Miceli, Giacomo Miceli, Steven Welch, Steven Welch, Kyu-Tae Sun, Kyu-Tae Sun, Taeddy Kim, Taeddy Kim, Jin-Moo Byun, Jin-Moo Byun, Sang-Hoon Jung, Sang-Hoon Jung, Moo-Young Seo, Moo-Young Seo, Hyun-Sok Kim, Hyun-Sok Kim, Dong-Gyu Park, Dong-Gyu Park, Jong-Mun Jeong, 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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