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Proceedings Paper

Highly sensitive focus monitoring technique based on illumination and target co-optimization
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Paper Abstract

We present a cost-effective focus monitoring technique based on the illumination and the target co-optimization. An advanced immersion scanner can provide the freeform illumination that enables the use of any kind of custom source shape by using a programmable array of thousands of individually adjustable micro-mirrors. Therefore, one can produce non-telecentricity using the asymmetric illumination in the scanner with the optimized focus target on the cost-effective binary OMOG mask. Then, the scanner focus variations directly translate into easily measurable overlay shifts in the printed pattern with high sensitivity (ΔShift/Δfocus = 60nm/100nm). In addition, the capability of using the freeform illumination allows us to computationally co-optimize the source and the focus target, simultaneously, generating not only vertical or horizontal shifts, but also introducing diagonal pattern shifts. The focus-induced pattern shifts can be accurately measured by standard wafer metrology tools such as CD-SEM and overlay metrology tools.

Paper Details

Date Published: 24 March 2016
PDF: 10 pages
Proc. SPIE 9778, Metrology, Inspection, and Process Control for Microlithography XXX, 977826 (24 March 2016); doi: 10.1117/12.2218647
Show Author Affiliations
Myungjun Lee, KLA-Tencor Corp. (United States)
Mark D. Smith, KLA-Tencor Corp. (United States)
Pradeep Subrahmanyan, KLA-Tencor Corp. (United States)
Ady Levy, KLA-Tencor Corp. (United States)

Published in SPIE Proceedings Vol. 9778:
Metrology, Inspection, and Process Control for Microlithography XXX
Martha I. Sanchez, Editor(s)

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