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Proceedings Paper

Recent CD AFM probe developments for sub-45 nm technology nodes
Author(s): Hao-Chih Liu; Jason R. Osborne; Gregory A. Dahlen; Johann Greschner; Thomas Bayer; Samuel Kalt; Georg Fritz
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Paper Abstract

This paper reports on new developments of advanced CD AFM probes after the prior introduction of "trident probes" in SPIE Advanced Lithography 2007 [1]. Trident probes, having sharpened extensions in the tip apex region, make possible bottom CD measurements within a few nanometers of the feature bottom corner; an area where other CD probes have difficulties due to tip shape limitations. Moreover, new metrology applications of trident probes have been developed for novel devices such as FinFET and vertical read/write hard disk heads. For ever smaller technology nodes, new probes evolved from the design of the trident probe. For example, the number of sharpened tip flares was reduced from three (trident) to two (bi-pod) to prevent possible interference of the third leg in the slow scan direction, as shown in Figure 3. Maintaining tip lateral stiffness as the tip size shrinks to less than 30 nm is vital for successful scanning. Consequently, a significant recent improvement is the change of probe shank cross-sectional geometry in order to maintain tip vertical aspect ratio of 1:5 (and lateral stiffness > 1 N/m). Finally, modifications of probe substrate are proposed and evaluated for current and new CD AFM systems. Hydrophobic, self-assembled monolayer (SAM) coatings were applied on CD probes to reduced tip "pull-away" distance1 during CD AFM scanning. Test results show that the pull away distance can be reduced more than 5 times on average (in some cases, by a factor of 15). Consequently, use of hydrophobic SAM coatings on CD probes mitigates pull-away distance thus allowing narrow trench CD measurements. We discuss limitations of prior CD AFM probes and design considerations of new CD probes. The characterization of first prototypes and evaluation of scan performance are presented in this work.

Paper Details

Date Published: 9 April 2008
PDF: 7 pages
Proc. SPIE 6922, Metrology, Inspection, and Process Control for Microlithography XXII, 69222J (9 April 2008); doi: 10.1117/12.773057
Show Author Affiliations
Hao-Chih Liu, Veeco Instruments, Inc. (United States)
Jason R. Osborne, Veeco Instruments, Inc. (United States)
Gregory A. Dahlen, Veeco Instruments, Inc. (United States)
Johann Greschner, Team Nanotec GmbH (Germany)
Thomas Bayer, Team Nanotec GmbH (Germany)
Samuel Kalt, Team Nanotec GmbH (Germany)
Georg Fritz, Team Nanotec GmbH (Germany)

Published in SPIE Proceedings Vol. 6922:
Metrology, Inspection, and Process Control for Microlithography XXII
John A. Allgair; Christopher J. Raymond, Editor(s)

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