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Proceedings Paper

Overlay metrology for double patterning processes
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Paper Abstract

The double patterning (DPT) process is foreseen by the industry to be the main solution for the 32 nm technology node and even beyond. Meanwhile process compatibility has to be maintained and the performance of overlay metrology has to improve. To achieve this for Image Based Overlay (IBO), usually the optics of overlay tools are improved. It was also demonstrated that these requirements are achievable with a Diffraction Based Overlay (DBO) technique named SCOLTM [1]. In addition, we believe that overlay measurements with respect to a reference grid are required to achieve the required overlay control [2]. This induces at least a three-fold increase in the number of measurements (2 for double patterned layers to the reference grid and 1 between the double patterned layers). The requirements of process compatibility, enhanced performance and large number of measurements make the choice of overlay metrology for DPT very challenging. In this work we use different flavors of the standard overlay metrology technique (IBO) as well as the new technique (SCOL) to address these three requirements. The compatibility of the corresponding overlay targets with double patterning processes (Litho-Etch-Litho-Etch (LELE); Litho-Freeze-Litho-Etch (LFLE), Spacer defined) is tested. The process impact on different target types is discussed (CD bias LELE, Contrast for LFLE). We compare the standard imaging overlay metrology with non-standard imaging techniques dedicated to double patterning processes (multilayer imaging targets allowing one overlay target instead of three, very small imaging targets). In addition to standard designs already discussed [1], we investigate SCOL target designs specific to double patterning processes. The feedback to the scanner is determined using the different techniques. The final overlay results obtained are compared accordingly. We conclude with the pros and cons of each technique and suggest the optimal metrology strategy for overlay control in double patterning processes.

Paper Details

Date Published: 23 March 2009
PDF: 9 pages
Proc. SPIE 7272, Metrology, Inspection, and Process Control for Microlithography XXIII, 72720G (23 March 2009); doi: 10.1117/12.814182
Show Author Affiliations
Philippe Leray, IMEC (Belgium)
Shaunee Cheng, IMEC (Belgium)
David Laidler, IMEC (Belgium)
Daniel Kandel, KLA-Tencor Corp. (Israel)
Mike Adel, KLA-Tencor Corp. (Israel)
Berta Dinu, KLA-Tencor Corp. (Israel)
Marco Polli, KLA-Tencor Corp. (Israel)
Mauro Vasconi, STMicroelectronics (Italy)
Bartlomiej Salski, QWED (Poland)


Published in SPIE Proceedings Vol. 7272:
Metrology, Inspection, and Process Control for Microlithography XXIII
John A. Allgair; Christopher J. Raymond, Editor(s)

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